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Curl-FAQ

on May 20, 2016

FAQ -- Frequently Asked Questions
Philosophy

1.1 What is cURL?
1.2 What is libcurl?
1.3 What is curl not?
1.4 When will you make curl do XXXX ?
1.5 Who makes curl?
1.6 What do you get for making curl?
1.7 What about CURL from curl.com?
1.8 I have a problem who do I mail?
1.9 Where do I buy commercial support for curl?
1.10 How many are using curl?
1.11 Why don't you update ca-bundle.crt
1.12 I have a problem who can I chat with?
1.13 curl's ECCN number?
1.14 How do I submit my patch?
1.15 How do I port libcurl to my OS?
Install Related Problems

2.1 configure doesn't find OpenSSL even when it is installed
2.1.1 native linker doesn't find OpenSSL
2.1.2 only the libssl lib is missing
2.2 Does curl work/build with other SSL libraries?
2.3 Where can I find a copy of LIBEAY32.DLL?
2.4 Does curl support SOCKS (RFC 1928) ?
2.5 Install libcurl for both 32bit and 64bit?
Usage Problems

3.1 curl: (1) SSL is disabled, https: not supported
3.2 How do I tell curl to resume a transfer?
3.3 Why doesn't my posting using -F work?
3.4 How do I tell curl to run custom FTP commands?
3.5 How can I disable the Accept: / header?
3.6 Does curl support ASP, XML, XHTML or HTML version Y?
3.7 Can I use curl to delete/rename a file through FTP?
3.8 How do I tell curl to follow HTTP redirects?
3.9 How do I use curl in my favorite programming language?
3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
3.11 How do I POST with a different Content-Type?
3.12 Why do FTP specific features over HTTP proxy fail?
3.13 Why does my single/double quotes fail?
3.14 Does curl support Javascript or PAC (automated proxy config)?
3.15 Can I do recursive fetches with curl?
3.16 What certificates do I need when I use SSL?
3.17 How do I list the root dir of an FTP server?
3.18 Can I use curl to send a POST/PUT and not wait for a response?
3.19 How do I get HTTP from a host using a specific IP address?
3.20 How to SFTP from my user's home directory?
3.21 Protocol xxx not supported or disabled in libcurl
3.22 curl -X gives me HTTP problems
Running Problems

4.1 Problems connecting to SSL servers.
4.2 Why do I get problems when I use & or % in the URL?
4.3 How can I use {, }, [ or ] to specify multiple URLs?
4.4 Why do I get downloaded data even though the web page doesn't exist?
4.5 Why do I get return code XXX from a HTTP server?
4.5.1 "400 Bad Request"
4.5.2 "401 Unauthorized"
4.5.3 "403 Forbidden"
4.5.4 "404 Not Found"
4.5.5 "405 Method Not Allowed"
4.5.6 "301 Moved Permanently"
4.6 Can you tell me what error code 142 means?
4.7 How do I keep user names and passwords secret in Curl command lines?
4.8 I found a bug!
4.9 Curl can't authenticate to the server that requires NTLM?
4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!
4.11 Why does my HTTP range requests return the full document?
4.12 Why do I get "certificate verify failed" ?
4.13 Why is curl -R on Windows one hour off?
4.14 Redirects work in browser but not with curl!
4.15 FTPS doesn't work
4.16 My HTTP POST or PUT requests are slow!
4.17 Non-functional connect timeouts on Windows
4.18 file:// URLs containing drive letters (Windows, NetWare)
4.19 Why doesn't cURL return an error when the network cable is unplugged?
4.20 curl doesn't return error for HTTP non-200 responses!
4.21 Why is there a HTTP/1.1 in my HTTP/2 request?
libcurl Issues

5.1 Is libcurl thread-safe?
5.2 How can I receive all data into a large memory chunk?
5.3 How do I fetch multiple files with libcurl?
5.4 Does libcurl do Winsock initing on win32 systems?
5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?
5.6 What about Keep-Alive or persistent connections?
5.7 Link errors when building libcurl on Windows!
5.8 libcurl.so.X: open failed: No such file or directory
5.9 How does libcurl resolve host names?
5.10 How do I prevent libcurl from writing the response to stdout?
5.11 How do I make libcurl not receive the whole HTTP response?
5.12 Can I make libcurl fake or hide my real IP address?
5.13 How do I stop an ongoing transfer?
5.14 Using C++ non-static functions for callbacks?
5.15 How do I get an FTP directory listing?
5.16 I want a different time-out!
5.17 Can I write a server with libcurl?
5.18 Does libcurl use threads?
License Issues

6.1 I have a GPL program, can I use the libcurl library?
6.2 I have a closed-source program, can I use the libcurl library?
6.3 I have a BSD licensed program, can I use the libcurl library?
6.4 I have a program that uses LGPL libraries, can I use libcurl?
6.5 Can I modify curl/libcurl for my program and keep the changes secret?
6.6 Can you please change the curl/libcurl license to XXXX?
6.7 What are my obligations when using libcurl in my commercial apps?
PHP/CURL Issues

7.1 What is PHP/CURL?
7.2 Who wrote PHP/CURL?
7.3 Can I perform multiple requests using the same handle?

  1. Philosophy

1.1 What is cURL?

cURL is the name of the project. The name is a play on 'Client for URLs', originally with URL spelled in uppercase to make it obvious it deals with URLs. The fact it can also be pronounced 'see URL' also helped, it works as an abbreviation for "Client URL Request Library" or why not the recursive version: "Curl URL Request Library".

The cURL project produces two products:

libcurl

A free and easy-to-use client-side URL transfer library, supporting DICT, FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3, POP3S, RTMP, RTSP, SCP, SFTP, SMB, SMBS, SMTP, SMTPS, TELNET and TFTP.

libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading, Kerberos, SPNEGO, HTTP form based upload, proxies, cookies, user+password authentication, file transfer resume, http proxy tunneling and more!

libcurl is highly portable, it builds and works identically on numerous platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HP-UX, IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, BeOS, Mac OS X, Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS, Symbian, OSF, Android, Minix, IBM TPF and more...

libcurl is free, thread-safe, IPv6 compatible, feature rich, well supported and fast.

curl

A command line tool for getting or sending files using URL syntax.

Since curl uses libcurl, curl supports the same wide range of common Internet protocols that libcurl does.

We pronounce curl with an initial k sound. It rhymes with words like girl and earl. This is a short WAV file to help you:

http://media.merriam-webster.com/soundc11/c/curl0001.wav
There are numerous sub-projects and related projects that also use the word curl in the project names in various combinations, but you should take notice that this FAQ is directed at the command-line tool named curl (and libcurl the library), and may therefore not be valid for other curl-related projects. (There is however a small section for the PHP/CURL in this FAQ.)

1.2 What is libcurl?

libcurl is a reliable and portable library which provides you with an easy interface to a range of common Internet protocols.

You can use libcurl for free in your application, be it open source, commercial or closed-source.

libcurl is most probably the most portable, most powerful and most often used C-based multi-platform file transfer library on this planet - be it open source or commercial.

1.3 What is curl not?

Curl is not a wget clone. That is a common misconception. Never, during curl's development, have we intended curl to replace wget or compete on its market. Curl is targeted at single-shot file transfers.

Curl is not a web site mirroring program. If you want to use curl to mirror something: fine, go ahead and write a script that wraps around curl to make it reality (like curlmirror.pl does).

Curl is not an FTP site mirroring program. Sure, get and send FTP with curl but if you want systematic and sequential behavior you should write a script (or write a new program that interfaces libcurl) and do it.

Curl is not a PHP tool, even though it works perfectly well when used from or with PHP (when using the PHP/CURL module).

Curl is not a program for a single operating system. Curl exists, compiles, builds and runs under a wide range of operating systems, including all modern Unixes (and a bunch of older ones too), Windows, Amiga, BeOS, OS/2, OS X, QNX etc.

1.4 When will you make curl do XXXX ?

We love suggestions of what to change in order to make curl and libcurl better. We do however believe in a few rules when it comes to the future of curl:

Curl -- the command line tool -- is to remain a non-graphical command line tool. If you want GUIs or fancy scripting capabilities, you should look for another tool that uses libcurl.

We do not add things to curl that other small and available tools already do very fine at the side. Curl's output is fine to pipe into another program or redirect to another file for the next program to interpret.

We focus on protocol related issues and improvements. If you wanna do more magic with the supported protocols than curl currently does, chances are big we will agree. If you wanna add more protocols, we may very well agree.

If you want someone else to make all the work while you wait for us to implement it for you, that is not a very friendly attitude. We spend a considerable time already on maintaining and developing curl. In order to get more out of us, you should consider trading in some of your time and efforts in return. Simply go to the GitHub repo which resides at https://github.com/curl/curl, fork the project, and create pull requests with your proposed changes.

If you write the code, chances are bigger that it will get into curl faster.

1.5 Who makes curl?

curl and libcurl are not made by any single individual. Daniel Stenberg is project leader and main developer, but other persons' submissions are important and crucial. Anyone can contribute and post their changes and improvements and have them inserted in the main sources (of course on the condition that developers agree on that the fixes are good).

The full list of all contributors is found in the docs/THANKS file.

curl is developed by a community, with Daniel at the wheel.

1.6 What do you get for making curl?

Project cURL is entirely free and open. No person gets paid for developing curl on full time. We do this voluntarily, mostly on spare time. Occasionally companies pay individual developers to work on curl, but that's up to each company and developer. It is not controlled by nor supervised in any way by the project.

We still get help from companies. Haxx provides web site, bandwidth, mailing lists etc, sourceforge.net hosts project services we take advantage from, like the bug tracker, and GitHub hosts the primary git repository at https://github.com/curl/curl. Also again, some companies have sponsored certain parts of the development in the past and I hope some will continue to do so in the future.

If you want to support our project, consider a donation or a banner-program or even better: by helping us coding, documenting, testing etc.

1.7 What about CURL from curl.com?

During the summer 2001, curl.com was busy advertising their client-side programming language for the web, named CURL.

We are in no way associated with curl.com or their CURL programming language.

Our project name curl has been in effective use since 1998. We were not the first computer related project to use the name "curl" and do not claim any rights to the name.

We recognize that we will be living in parallel with curl.com and wish them every success.

1.8 I have a problem who do I mail?

Please do not mail any single individual unless you really need to. Keep curl-related questions on a suitable mailing list. All available mailing lists are listed in the MANUAL document and online at https://curl.haxx.se/mail/

Keeping curl-related questions and discussions on mailing lists allows others to join in and help, to share their ideas, contribute their suggestions and spread their wisdom. Keeping discussions on public mailing lists also allows for others to learn from this (both current and future users thanks to the web based archives of the mailing lists), thus saving us from having to repeat ourselves even more. Thanks for respecting this.

If you have found or simply suspect a security problem in curl or libcurl, mail curl-security at haxx.se (closed list of receivers, mails are not disclosed) and tell. Then we can produce a fix in a timely manner before the flaw is announced to the world, thus lessen the impact the problem will have on existing users.

1.9 Where do I buy commercial support for curl?

curl is fully open source. It means you can hire any skilled engineer to fix your curl-related problems.

We list available alternatives on the curl web site: https://curl.haxx.se/support.html

1.10 How many are using curl?

It is impossible to tell.

We don't know how many users that knowingly have installed and use curl.

We don't know how many users that use curl without knowing that they are in fact using it.

We don't know how many users that downloaded or installed curl and then never use it.

In May 2012 Daniel did a counting game and came up with a number that may be completely wrong or somewhat accurate. Over 500 million!

See https://daniel.haxx.se/blog/2012/05/16/300m-users/

1.11 Why don't you update ca-bundle.crt

The ca cert bundle that used to shipped with curl was very outdated and must be replaced with an up-to-date version by anyone who wants to verify peers. It is no longer provided by curl. The last curl release ever that shipped a ca cert bundle was curl 7.18.0.

In the cURL project we've decided not to attempt to keep this file updated (or even present anymore) since deciding what to add to a ca cert bundle is an undertaking we've not been ready to accept, and the one we can get from Mozilla is perfectly fine so there's no need to duplicate that work.

Today, with many services performed over HTTPS, every operating system should come with a default ca cert bundle that can be deemed somewhat trustworthy and that collection (if reasonably updated) should be deemed to be a lot better than a private curl version.

If you want the most recent collection of ca certs that Mozilla Firefox uses, we recommend that you extract the collection yourself from Mozilla Firefox (by running 'make ca-bundle), or by using our online service setup for this purpose: https://curl.haxx.se/docs/caextract.html

1.12 I have a problem who can I chat with?

There's a bunch of friendly people hanging out in the #curl channel on the IRC network irc.freenode.net. If you're polite and nice, chances are big that you can get -- or provide -- help instantly.

1.13 curl's ECCN number?

The US government restricts exports of software that contains or uses cryptography. When doing so, the Export Control Classification Number (ECCN) is used to identify the level of export control etc.

Apache Software Foundation gives a good explanation of ECCNs at https://www.apache.org/dev/crypto.html

We believe curl's number might be ECCN 5D002, another possibility is 5D992. It seems necessary to write them (the authority that administers ECCN numbers), asking to confirm.

Comprehensible explanations of the meaning of such numbers and how to obtain them (resp.) are here

http://www.bis.doc.gov/licensing/exportingbasics.htm http://www.bis.doc.gov/licensing/do_i_needaneccn.html

An incomprehensible description of the two numbers above is here http://www.access.gpo.gov/bis/ear/pdf/ccl5-pt2.pdf

1.14 How do I submit my patch?

When you have made a patch or a change of whatever sort, and want to submit that to the project, there are a few different ways we prefer:

o send a patch to the curl-library mailing list. We're many subscribers

there and there are lots of people who can review patches, comment on them and "receive" them properly.

o if your patch changes or fixes a bug, you can also opt to submit a bug

report in the bug tracker and attach your patch there. There are less people involved there.

Lots of more details are found in the CONTRIBUTE and INTERNALS docs.

1.15 How do I port libcurl to my OS?

Here's a rough step-by-step:

  1. copy a suitable lib/config-*.h file as a start to lib/config-[youros].h

  2. edit lib/config-[youros].h to match your OS and setup

  3. edit lib/curl_setup.h to include config-[youros].h when your OS is

    detected by the preprocessor, in the style others already exist

  4. compile lib/*.c and make them into a library

  5. Install Related Problems

2.1 configure doesn't find OpenSSL even when it is installed

This may be because of several reasons.

2.1.1 native linker doesn't find openssl

Affected platforms:

Solaris (native cc compiler)
HPUX (native cc compiler)
SGI IRIX (native cc compiler)
SCO UNIX (native cc compiler)
When configuring curl, I specify --with-ssl. OpenSSL is installed in /usr/local/ssl Configure reports SSL in /usr/local/ssl, but fails to find CRYPTO_lock in -lcrypto

Cause: The cc for this test places the -L/usr/local/ssl/lib AFTER -lcrypto, so ld can't find the library. This is due to a bug in the GNU autoconf tool.

Workaround: Specifying "LDFLAGS=-L/usr/local/ssl/lib" in front of ./configure places the -L/usr/local/ssl/lib early enough in the command line to make things work

2.1.2 only the libssl lib is missing

If all include files and the libcrypto lib is present, with only the libssl being missing according to configure, this is mostly likely because a few functions are left out from the libssl.

If the function names missing include RSA or RSAREF you can be certain that this is because libssl requires the RSA and RSAREF libs to build.

See the INSTALL file section that explains how to add those libs to configure. Make sure that you remove the config.cache file before you rerun configure with the new flags.

2.2 Does curl work/build with other SSL libraries?

Curl has been written to use a generic SSL function layer internally, and that SSL functionality can then be provided by one out of many different SSL backends.

curl can be built to use one of the following SSL alternatives: OpenSSL, GnuTLS, yassl, NSS, PolarSSL, axTLS, Secure Transport (native iOS/OS X), WinSSL (native Windows) or GSKit (native IBM i). They all have their pros and cons, and we try to maintain a comparison of them here: https://curl.haxx.se/docs/ssl-compared.html

2.3 Where can I find a copy of LIBEAY32.DLL?

That is an OpenSSL binary built for Windows.

Curl can be built with OpenSSL to do the SSL stuff. The LIBEAY32.DLL is then what curl needs on a windows machine to do https:// etc. Check out the curl web site to find accurate and up-to-date pointers to recent OpenSSL DLLs and other binary packages.

2.4 Does curl support SOCKS (RFC 1928) ?

Yes, SOCKS 4 and 5 are supported.

2.5 Install libcurl for both 32bit and 64bit?

In curl's configure procedure one of the regular include files get created with platform specific information. The file 'curl/curlbuild.h' in the installed libcurl file tree is therefore somewhat tied to that particular platform.

To allow applications to get built for either 32bit or 64bit you need to install libcurl headers for both setups and unfortunately curl doesn't do this automatically.

A commonly used procedure is this:

$ ./configure [32bit platform]
$ mv curl/curlbuild.h curl/curlbuild-32bit.h
$ ./configure [64bit platform]
$ mv curl/curlbuild.h curl/curlbuild-64bit.h
Then you make a toplevel curl/curlbuild.h replacement that only does this:

ifdef IS_32BIT

include "curlbuild-32bit.h"

else

include "curlbuild-64bit.h"

endif

  1. Usage problems

3.1 curl: (1) SSL is disabled, https: not supported

If you get this output when trying to get anything from a https:// server, it means that the instance of curl/libcurl that you're using was built without support for this protocol.

This could've happened if the configure script that was run at build time couldn't find all libs and include files curl requires for SSL to work. If the configure script fails to find them, curl is simply built without SSL support.

To get the https:// support into a curl that was previously built but that reports that https:// is not supported, you should dig through the document and logs and check out why the configure script doesn't find the SSL libs and/or include files.

Also, check out the other paragraph in this FAQ labelled "configure doesn't find OpenSSL even when it is installed".

3.2 How do I tell curl to resume a transfer?

Curl supports resumed transfers both ways on both FTP and HTTP. Try the -C option.

3.3 Why doesn't my posting using -F work?

You can't simply use -F or -d at your choice. The web server that will receive your post expects one of the formats. If the form you're trying to submit uses the type 'multipart/form-data', then and only then you must use the -F type. In all the most common cases, you should use -d which then causes a posting with the type 'application/x-www-form-urlencoded'.

This is described in some detail in the MANUAL and TheArtOfHttpScripting documents, and if you don't understand it the first time, read it again before you post questions about this to the mailing list. Also, try reading through the mailing list archives for old postings and questions regarding this.

3.4 How do I tell curl to run custom FTP commands?

You can tell curl to perform optional commands both before and/or after a file transfer. Study the -Q/--quote option.

Since curl is used for file transfers, you don't normally use curl to perform FTP commands without transferring anything. Therefore you must always specify a URL to transfer to/from even when doing custom FTP commands, or use -I which implies the "no body" option sent to libcurl.

3.5 How can I disable the Accept: / header?

You can change all internally generated headers by adding a replacement with the -H/--header option. By adding a header with empty contents you safely disable that one. Use -H "Accept:" to disable that specific header.

3.6 Does curl support ASP, XML, XHTML or HTML version Y?

To curl, all contents are alike. It doesn't matter how the page was generated. It may be ASP, PHP, Perl, shell-script, SSI or plain HTML files. There's no difference to curl and it doesn't even know what kind of language that generated the page.

See also item 3.14 regarding javascript.

3.7 Can I use curl to delete/rename a file through FTP?

Yes. You specify custom FTP commands with -Q/--quote.

One example would be to delete a file after you have downloaded it:

curl -O ftp://download.com/coolfile -Q '-DELE coolfile'
or rename a file after upload:

curl -T infile ftp://upload.com/dir/ -Q "-RNFR infile" -Q "-RNTO newname"
3.8 How do I tell curl to follow HTTP redirects?

Curl does not follow so-called redirects by default. The Location: header that informs the client about this is only interpreted if you're using the -L/--location option. As in:

curl -L http://redirector.com
Not all redirects are HTTP ones, see 4.14

3.9 How do I use curl in my favorite programming language?

There exist many language interfaces/bindings for curl that integrates it better with various languages. If you are fluid in a script language, you may very well opt to use such an interface instead of using the command line tool.

Find out more about which languages that support curl directly, and how to install and use them, in the libcurl section of the curl web site: https://curl.haxx.se/libcurl/

All the various bindings to libcurl are made by other projects and people, outside of the cURL project. The cURL project itself only produces libcurl with its plain C API. If you don't find anywhere else to ask you can ask about bindings on the curl-library list too, but be prepared that people on that list may not know anything about bindings.

In October 2009, there were interfaces available for the following languages: Ada95, Basic, C, C++, Ch, Cocoa, D, Dylan, Eiffel, Euphoria, Ferite, Gambas, glib/GTK+, Haskell, ILE/RPG, Java, Lisp, Lua, Mono, .NET, Object-Pascal, O'Caml, Pascal, Perl, PHP, PostgreSQL, Python, R, Rexx, Ruby, Scheme, S-Lang, Smalltalk, SP-Forth, SPL, Tcl, Visual Basic, Visual FoxPro, Q, wxwidgets and XBLite. By the time you read this, additional ones may have appeared!

3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?

Curl adheres to the HTTP spec, which basically means you can play with any protocol that is built on top of HTTP. Protocols such as SOAP, WEBDAV and XML-RPC are all such ones. You can use -X to set custom requests and -H to set custom headers (or replace internally generated ones).

Using libcurl is of course just as fine and you'd just use the proper library options to do the same.

3.11 How do I POST with a different Content-Type?

You can always replace the internally generated headers with -H/--header. To make a simple HTTP POST with text/xml as content-type, do something like:

curl -d "datatopost" -H "Content-Type: text/xml" [URL]
3.12 Why do FTP specific features over HTTP proxy fail?

Because when you use a HTTP proxy, the protocol spoken on the network will be HTTP, even if you specify a FTP URL. This effectively means that you normally can't use FTP specific features such as FTP upload and FTP quote etc.

There is one exception to this rule, and that is if you can "tunnel through" the given HTTP proxy. Proxy tunneling is enabled with a special option (-p) and is generally not available as proxy admins usually disable tunneling to other ports than 443 (which is used for HTTPS access through proxies).

3.13 Why does my single/double quotes fail?

To specify a command line option that includes spaces, you might need to put the entire option within quotes. Like in:

curl -d " with spaces " url.com

or perhaps

curl -d ' with spaces ' url.com

Exactly what kind of quotes and how to do this is entirely up to the shell or command line interpreter that you are using. For most unix shells, you can more or less pick either single (') or double (") quotes. For Windows/DOS prompts I believe you're forced to use double (") quotes.

Please study the documentation for your particular environment. Examples in the curl docs will use a mix of both these ones as shown above. You must adjust them to work in your environment.

Remember that curl works and runs on more operating systems than most single individuals have ever tried.

3.14 Does curl support Javascript or PAC (automated proxy config)?

Many web pages do magic stuff using embedded Javascript. Curl and libcurl have no built-in support for that, so it will be treated just like any other contents.

.pac files are a netscape invention and are sometimes used by organizations to allow them to differentiate which proxies to use. The .pac contents is just a Javascript program that gets invoked by the browser and that returns the name of the proxy to connect to. Since curl doesn't support Javascript, it can't support .pac proxy configuration either.

Some workarounds usually suggested to overcome this Javascript dependency:

Depending on the Javascript complexity, write up a script that translates it to another language and execute that.

Read the Javascript code and rewrite the same logic in another language.

Implement a Javascript interpreter, people have successfully used the Mozilla Javascript engine in the past.

Ask your admins to stop this, for a static proxy setup or similar.

3.15 Can I do recursive fetches with curl?

No. curl itself has no code that performs recursive operations, such as those performed by wget and similar tools.

There exist wrapper scripts with that functionality (for example the curlmirror perl script), and you can write programs based on libcurl to do it, but the command line tool curl itself cannot.

3.16 What certificates do I need when I use SSL?

There are three different kinds of "certificates" to keep track of when we talk about using SSL-based protocols (HTTPS or FTPS) using curl or libcurl.

CLIENT CERTIFICATE

The server you communicate may require that you can provide this in order to prove that you actually are who you claim to be. If the server doesn't require this, you don't need a client certificate.

A client certificate is always used together with a private key, and the private key has a pass phrase that protects it.

SERVER CERTIFICATE

The server you communicate with has a server certificate. You can and should verify this certificate to make sure that you are truly talking to the real server and not a server impersonating it.

CERTIFICATE AUTHORITY CERTIFICATE ("CA cert")

You often have several CA certs in a CA cert bundle that can be used to verify a server certificate that was signed by one of the authorities in the bundle. curl does not come with a CA cert bundle but most curl installs provide one. You can also override the default.

The server certificate verification process is made by using a Certificate Authority certificate ("CA cert") that was used to sign the server certificate. Server certificate verification is enabled by default in curl and libcurl and is often the reason for problems as explained in FAQ entry 4.12 and the SSLCERTS document (https://curl.haxx.se/docs/sslcerts.html). Server certificates that are "self-signed" or otherwise signed by a CA that you do not have a CA cert for, cannot be verified. If the verification during a connect fails, you are refused access. You then need to explicitly disable the verification to connect to the server.

3.17 How do I list the root dir of an FTP server?

There are two ways. The way defined in the RFC is to use an encoded slash in the first path part. List the "/tmp" dir like this:

curl ftp://ftp.sunet.se/%2ftmp/
or the not-quite-kosher-but-more-readable way, by simply starting the path section of the URL with a slash:

curl ftp://ftp.sunet.se//tmp/
3.18 Can I use curl to send a POST/PUT and not wait for a response?

No.

But you could easily write your own program using libcurl to do such stunts.

3.19 How do I get HTTP from a host using a specific IP address?

For example, you may be trying out a web site installation that isn't yet in the DNS. Or you have a site using multiple IP addresses for a given host name and you want to address a specific one out of the set.

Set a custom Host: header that identifies the server name you want to reach but use the target IP address in the URL:

curl --header "Host: www.example.com" http://127.0.0.1/

You can also opt to add faked host name entries to curl with the --resolve option. That has the added benefit that things like redirects will also work properly. The above operation would instead be done as:

curl --resolve www.example.com:80:127.0.0.1 http://www.example.com/

3.20 How to SFTP from my user's home directory?

Contrary to how FTP works, SFTP and SCP URLs specify the exact directory to work with. It means that if you don't specify that you want the user's home directory, you get the actual root directory.

To specify a file in your user's home directory, you need to use the correct URL syntax which for sftp might look similar to:

curl -O -u user:password sftp://example.com/~/file.txt

and for SCP it is just a different protocol prefix:

curl -O -u user:password scp://example.com/~/file.txt

3.21 Protocol xxx not supported or disabled in libcurl

When passing on a URL to curl to use, it may respond that the particular protocol is not supported or disabled. The particular way this error message is phrased is because curl doesn't make a distinction internally of whether a particular protocol is not supported (i.e. never got any code added that knows how to speak that protocol) or if it was explicitly disabled. curl can be built to only support a given set of protocols, and the rest would then be disabled or not supported.

Note that this error will also occur if you pass a wrongly spelled protocol part as in "htpt://example.com" or as in the less evident case if you prefix the protocol part with a space as in " http://example.com/".

3.22 curl -X gives me HTTP problems

In normal circumstances, -X should hardly ever be used.

By default you use curl without explicitly saying which request method to use when the URL identifies a HTTP transfer. If you just pass in a URL like "curl http://example.com" it will use GET. If you use -d or -F curl will use POST, -I will cause a HEAD and -T will make it a PUT.

If for whatever reason you're not happy with these default choices that curl does for you, you can override those request methods by specifying -X [WHATEVER]. This way you can for example send a DELETE by doing "curl -X DELETE [URL]".

It is thus pointless to do "curl -XGET [URL]" as GET would be used anyway. In the same vein it is pointless to do "curl -X POST -d data [URL]"... But you can make a fun and somewhat rare request that sends a request-body in a GET request with something like "curl -X GET -d data [URL]"

Note that -X doesn't actually change curl's behavior as it only modifies the actual string sent in the request, but that may of course trigger a different set of events.

Accordingly, by using -XPOST on a command line that for example would follow a 303 redirect, you will effectively prevent curl from behaving correctly. Be aware.

  1. Running Problems

4.1 Problems connecting to SSL servers.

It took a very long time before we could sort out why curl had problems to connect to certain SSL servers when using SSLeay or OpenSSL v0.9+. The error sometimes showed up similar to:

16570:error:1407D071:SSL routines:SSL2_READ:bad mac decode:s2_pkt.c:233:

It turned out to be because many older SSL servers don't deal with SSLv3 requests properly. To correct this problem, tell curl to select SSLv2 from the command line (-2/--sslv2).

There have also been examples where the remote server didn't like the SSLv2 request and instead you had to force curl to use SSLv3 with -3/--sslv3.

4.2 Why do I get problems when I use & or % in the URL?

In general unix shells, the & symbol is treated specially and when used, it runs the specified command in the background. To safely send the & as a part of a URL, you should quote the entire URL by using single (') or double (") quotes around it. Similar problems can also occur on some shells with other characters, including ?*!$~(){}<>|;`. When in doubt, quote the URL.

An example that would invoke a remote CGI that uses &-symbols could be:

curl 'http://www.altavista.com/cgi-bin/query?text=yes&q=curl'
In Windows, the standard DOS shell treats the percent sign specially and you need to use TWO percent signs for each single one you want to use in the URL.

If you want a literal percent sign to be part of the data you pass in a POST using -d/--data you must encode it as '%25' (which then also needs the percent sign doubled on Windows machines).

4.3 How can I use {, }, [ or ] to specify multiple URLs?

Because those letters have a special meaning to the shell, and to be used in a URL specified to curl you must quote them.

An example that downloads two URLs (sequentially) would do:

curl '{curl,www}.haxx.se'

To be able to use those letters as actual parts of the URL (without using them for the curl URL "globbing" system), use the -g/--globoff option:

curl -g 'www.site.com/weirdname[].html'

4.4 Why do I get downloaded data even though the web page doesn't exist?

Curl asks remote servers for the page you specify. If the page doesn't exist at the server, the HTTP protocol defines how the server should respond and that means that headers and a "page" will be returned. That's simply how HTTP works.

By using the --fail option you can tell curl explicitly to not get any data if the HTTP return code doesn't say success.

4.5 Why do I get return code XXX from a HTTP server?

RFC2616 clearly explains the return codes. This is a short transcript. Go read the RFC for exact details:

4.5.1 "400 Bad Request"

The request could not be understood by the server due to malformed syntax. The client SHOULD NOT repeat the request without modifications.

4.5.2 "401 Unauthorized"

The request requires user authentication.

4.5.3 "403 Forbidden"

The server understood the request, but is refusing to fulfil it. Authorization will not help and the request SHOULD NOT be repeated.

4.5.4 "404 Not Found"

The server has not found anything matching the Request-URI. No indication is given of whether the condition is temporary or permanent.

4.5.5 "405 Method Not Allowed"

The method specified in the Request-Line is not allowed for the resource identified by the Request-URI. The response MUST include an Allow header containing a list of valid methods for the requested resource.

4.5.6 "301 Moved Permanently"

If you get this return code and an HTML output similar to this:

Moved Permanently

The document has moved here.
it might be because you request a directory URL but without the trailing slash. Try the same operation again with the trailing URL, or use the -L/--location option to follow the redirection.

4.6 Can you tell me what error code 142 means?

All curl error codes are described at the end of the man page, in the section called "EXIT CODES".

Error codes that are larger than the highest documented error code means that curl has exited due to a crash. This is a serious error, and we appreciate a detailed bug report from you that describes how we could go ahead and repeat this!

4.7 How do I keep user names and passwords secret in Curl command lines?

This problem has two sides:

The first part is to avoid having clear-text passwords in the command line so that they don't appear in 'ps' outputs and similar. That is easily avoided by using the "-K" option to tell curl to read parameters from a file or stdin to which you can pass the secret info. curl itself will also attempt to "hide" the given password by blanking out the option - this doesn't work on all platforms.

To keep the passwords in your account secret from the rest of the world is not a task that curl addresses. You could of course encrypt them somehow to at least hide them from being read by human eyes, but that is not what anyone would call security.

Also note that regular HTTP (using Basic authentication) and FTP passwords are sent in clear across the network. All it takes for anyone to fetch them is to listen on the network. Eavesdropping is very easy. Use more secure authentication methods (like Digest, Negotiate or even NTLM) or consider the SSL-based alternatives HTTPS and FTPS.

4.8 I found a bug!

It is not a bug if the behavior is documented. Read the docs first. Especially check out the KNOWN_BUGS file, it may be a documented bug!

If it is a problem with a binary you've downloaded or a package for your particular platform, try contacting the person who built the package/archive you have.

If there is a bug, read the BUGS document first. Then report it as described in there.

4.9 Curl can't authenticate to the server that requires NTLM?

NTLM support requires OpenSSL, GnuTLS, NSS, Secure Transport, or Microsoft Windows libraries at build-time to provide this functionality.

NTLM is a Microsoft proprietary protocol. Proprietary formats are evil. You should not use such ones.

4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!

Many web servers allow or demand that the administrator configures the server properly for these requests to work on the web server.

Some servers seem to support HEAD only on certain kinds of URLs.

To fully grasp this, try the documentation for the particular server software you're trying to interact with. This is not anything curl can do anything about.

4.11 Why does my HTTP range requests return the full document?

Because the range may not be supported by the server, or the server may choose to ignore it and return the full document anyway.

4.12 Why do I get "certificate verify failed" ?

You invoke curl 7.10 or later to communicate on a https:// URL and get an error back looking something similar to this:

curl: (35) SSL: error:14090086:SSL routines:
SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
Then it means that curl couldn't verify that the server's certificate was good. Curl verifies the certificate using the CA cert bundle that comes with the curl installation.

To disable the verification (which makes it act like curl did before 7.10), use -k. This does however enable man-in-the-middle attacks.

If you get this failure but are having a CA cert bundle installed and used, the server's certificate is not signed by one of the CA's in the bundle. It might for example be self-signed. You then correct this problem by obtaining a valid CA cert for the server. Or again, decrease the security by disabling this check.

Details are also in the SSLCERTS file in the release archives, found online here: https://curl.haxx.se/docs/sslcerts.html

4.13 Why is curl -R on Windows one hour off?

During daylight savings time, when -R is used, curl will set a time that appears one hour off. This happens due to a flaw in how Windows stores and uses file modification times and it is not easily worked around. For details on this problem, read this: http://www.codeproject.com/datetime/dstbugs.asp

4.14 Redirects work in browser but not with curl!

curl supports HTTP redirects fine (see item 3.8). Browsers generally support at least two other ways to perform redirects that curl does not:

Meta tags. You can write a HTML tag that will cause the browser to redirect to another given URL after a certain time.

Javascript. You can write a Javascript program embedded in a HTML page that redirects the browser to another given URL.

There is no way to make curl follow these redirects. You must either manually figure out what the page is set to do, or you write a script that parses the results and fetches the new URL.

4.15 FTPS doesn't work

curl supports FTPS (sometimes known as FTP-SSL) both implicit and explicit mode.

When a URL is used that starts with FTPS://, curl assumes implicit SSL on the control connection and will therefore immediately connect and try to speak SSL. FTPS:// connections default to port 990.

To use explicit FTPS, you use a FTP:// URL and the --ftp-ssl option (or one of its related flavours). This is the most common method, and the one mandated by RFC4217. This kind of connection then of course uses the standard FTP port 21 by default.

4.16 My HTTP POST or PUT requests are slow!

libcurl makes all POST and PUT requests (except for POST requests with a very tiny request body) use the "Expect: 100-continue" header. This header allows the server to deny the operation early so that libcurl can bail out already before having to send any data. This is useful in authentication cases and others.

However, many servers don't implement the Expect: stuff properly and if the server doesn't respond (positively) within 1 second libcurl will continue and send off the data anyway.

You can disable libcurl's use of the Expect: header the same way you disable any header, using -H / CURLOPT_HTTPHEADER, or by forcing it to use HTTP 1.0.

4.17 Non-functional connect timeouts

In most Windows setups having a timeout longer than 21 seconds make no difference, as it will only send 3 TCP SYN packets and no more. The second packet sent three seconds after the first and the third six seconds after the second. No more than three packets are sent, no matter how long the timeout is set.

See option TcpMaxConnectRetransmissions on this page: https://support.microsoft.com/en-us/kb/175523/en-us

Also, even on non-Windows systems there may run a firewall or anti-virus software or similar that accepts the connection but does not actually do anything else. This will make (lib)curl to consider the connection connected and thus the connect timeout won't trigger.

4.18 file:// URLs containing drive letters (Windows, NetWare)

When using cURL to try to download a local file, one might use a URL in this format:

file://D:/blah.txt

You'll find that even if D:\blah.txt does exist, cURL returns a 'file not found' error.

According to RFC 1738 (https://www.ietf.org/rfc/rfc1738.txt), file:// URLs must contain a host component, but it is ignored by most implementations. In the above example, 'D:' is treated as the host component, and is taken away. Thus, cURL tries to open '/blah.txt'. If your system is installed to drive C:, that will resolve to 'C:\blah.txt', and if that doesn't exist you will get the not found error.

To fix this problem, use file:// URLs with three leading slashes:

file:///D:/blah.txt

Alternatively, if it makes more sense, specify 'localhost' as the host component:

file://localhost/D:/blah.txt

In either case, cURL should now be looking for the correct file.

4.19 Why doesn't cURL return an error when the network cable is unplugged?

Unplugging a cable is not an error situation. The TCP/IP protocol stack was designed to be fault tolerant, so even though there may be a physical break somewhere the connection shouldn't be affected, just possibly delayed. Eventually, the physical break will be fixed or the data will be re-routed around the physical problem through another path.

In such cases, the TCP/IP stack is responsible for detecting when the network connection is irrevocably lost. Since with some protocols it is perfectly legal for the client to wait indefinitely for data, the stack may never report a problem, and even when it does, it can take up to 20 minutes for it to detect an issue. The curl option --keepalive-time enables keep-alive support in the TCP/IP stack which makes it periodically probe the connection to make sure it is still available to send data. That should reliably detect any TCP/IP network failure.

But even that won't detect the network going down before the TCP/IP connection is established (e.g. during a DNS lookup) or using protocols that don't use TCP. To handle those situations, curl offers a number of timeouts on its own. --speed-limit/--speed-time will abort if the data transfer rate falls too low, and --connect-timeout and --max-time can be used to put an overall timeout on the connection phase or the entire transfer.

A libcurl-using application running in a known physical environment (e.g. an embedded device with only a single network connection) may want to act immediately if its lone network connection goes down. That can be achieved by having the application monitor the network connection on its own using an OS-specific mechanism, then signalling libcurl to abort (see also item 5.13).

4.20 curl doesn't return error for HTTP non-200 responses!

Correct. Unless you use -f (--fail).

When doing HTTP transfers, curl will perform exactly what you're asking it to do and if successful it will not return an error. You can use curl to test your web server's "file not found" page (that gets 404 back), you can use it to check your authentication protected web pages (that get a 401 back) and so on.

The specific HTTP response code does not constitute a problem or error for curl. It simply sends and delivers HTTP as you asked and if that worked, everything is fine and dandy. The response code is generally providing more higher level error information that curl doesn't care about. The error was not in the HTTP transfer.

If you want your command line to treat error codes in the 400 and up range as errors and thus return a non-zero value and possibly show an error message, curl has a dedicated option for that: -f (CURLOPT_FAILONERROR in libcurl speak).

You can also use the -w option and the variable %{response_code} to extract the exact response code that was return in the response.

4.21 Why is there a HTTP/1.1 in my HTTP/2 request?

If you use verbose to see the HTTP request when you send off a HTTP/2 request, it will still say 1.1.

The reason for this is that we first generate the request to send using the old 1.1 style and show that request in the verbose output, and then we convert it over to the binary header-compressed HTTP/2 style. The actual "1.1" part from that request is then not actually used in the transfer. The binary HTTP/2 headers are not human readable.

  1. libcurl Issues

5.1 Is libcurl thread-safe?

Yes.

We have written the libcurl code specifically adjusted for multi-threaded programs. libcurl will use thread-safe functions instead of non-safe ones if your system has such. Note that you must never share the same handle in multiple threads.

There may be some exceptions to thread safety depending on how libcurl was built. Please review the guidelines for thread safety to learn more: https://curl.haxx.se/libcurl/c/threadsafe.html

5.2 How can I receive all data into a large memory chunk?

[ See also the examples/getinmemory.c source ]

You are in full control of the callback function that gets called every time there is data received from the remote server. You can make that callback do whatever you want. You do not have to write the received data to a file.

One solution to this problem could be to have a pointer to a struct that you pass to the callback function. You set the pointer using the CURLOPT_WRITEDATA option. Then that pointer will be passed to the callback instead of a FILE * to a file:

/ imaginary struct /
struct MemoryStruct {
char memory;
size_t size;
};
/
imaginary callback function /
size_t
WriteMemoryCallback(void
ptr, size_t size, size_t nmemb, void data)
{
size_t realsize = size
nmemb;
struct MemoryStruct mem = (struct MemoryStruct )data;
mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);
if (mem->memory) {
memcpy(&(mem->memory[mem->size]), ptr, realsize);
mem->size += realsize;
mem->memory[mem->size] = 0;
}
return realsize;
}
5.3 How do I fetch multiple files with libcurl?

libcurl has excellent support for transferring multiple files. You should just repeatedly set new URLs with curl_easy_setopt() and then transfer it with curl_easy_perform(). The handle you get from curl_easy_init() is not only reusable, but you're even encouraged to reuse it if you can, as that will enable libcurl to use persistent connections.

5.4 Does libcurl do Winsock initialization on win32 systems?

Yes, if told to in the curl_global_init() call.

5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?

Yes, but you cannot open a FILE and pass the pointer to a DLL and have that DLL use the FILE (as the DLL and the client application cannot access each others' variable memory areas). If you set CURLOPT_WRITEDATA you must also use CURLOPT_WRITEFUNCTION as well to set a function that writes the file, even if that simply writes the data to the specified FILE *. Similarly, if you use CURLOPT_READDATA you must also specify CURLOPT_READFUNCTION.

5.6 What about Keep-Alive or persistent connections?

curl and libcurl have excellent support for persistent connections when transferring several files from the same server. Curl will attempt to reuse connections for all URLs specified on the same command line/config file, and libcurl will reuse connections for all transfers that are made using the same libcurl handle.

When you use the easy interface, the connection cache is kept within the easy handle. If you instead use the multi interface, the connection cache will be kept within the multi handle and will be shared among all the easy handles that are used within the same multi handle.

5.7 Link errors when building libcurl on Windows!

You need to make sure that your project, and all the libraries (both static and dynamic) that it links against, are compiled/linked against the same run time library.

This is determined by the /MD, /ML, /MT (and their corresponding /M?d) options to the command line compiler. /MD (linking against MSVCRT dll) seems to be the most commonly used option.

When building an application that uses the static libcurl library, you must add -DCURL_STATICLIB to your CFLAGS. Otherwise the linker will look for dynamic import symbols. If you're using Visual Studio, you need to instead add CURL_STATICLIB in the "Preprocessor Definitions" section.

If you get linker error like "unknown symbol impcurl_easy_init ..." you have linked against the wrong (static) library. If you want to use the libcurl.dll and import lib, you don't need any extra CFLAGS, but use one of the import libraries below. These are the libraries produced by the various lib/Makefile.* files:

Target: static lib. import lib for libcurl*.dll.

MingW: libcurl.a libcurldll.a
MSVC (release): libcurl.lib libcurl_imp.lib
MSVC (debug): libcurld.lib libcurld_imp.lib
Borland: libcurl.lib libcurl_imp.lib
5.8 libcurl.so.X: open failed: No such file or directory

This is an error message you might get when you try to run a program linked with a shared version of libcurl and your run-time linker (ld.so) couldn't find the shared library named libcurl.so.X. (Where X is the number of the current libcurl ABI, typically 3 or 4).

You need to make sure that ld.so finds libcurl.so.X. You can do that multiple ways, and it differs somewhat between different operating systems, but they are usually:

  • Add an option to the linker command line that specify the hard-coded path

the run-time linker should check for the lib (usually -R)

  • Set an environment variable (LD_LIBRARY_PATH for example) where ld.so

should check for libs

  • Adjust the system's config to check for libs in the directory where you've

put the dir (like Linux's /etc/ld.so.conf)

'man ld.so' and 'man ld' will tell you more details

5.9 How does libcurl resolve host names?

libcurl supports a large a number of different name resolve functions. One of them is picked at build-time and will be used unconditionally. Thus, if you want to change name resolver function you must rebuild libcurl and tell it to use a different function.

  • The non-IPv6 resolver that can use one out of four host name resolve calls

(depending on what your system supports):

A - gethostbyname()
B - gethostbyname_r() with 3 arguments
C - gethostbyname_r() with 5 arguments
D - gethostbyname_r() with 6 arguments

  • The IPv6-resolver that uses getaddrinfo()

  • The c-ares based name resolver that uses the c-ares library for resolves.

Using this offers asynchronous name resolves.

  • The threaded resolver (default option on Windows). It uses:

    A - gethostbyname() on plain IPv4 hosts
    B - getaddrinfo() on IPv6 enabled hosts
    Also note that libcurl never resolves or reverse-lookups addresses given as pure numbers, such as 127.0.0.1 or ::1.

5.10 How do I prevent libcurl from writing the response to stdout?

libcurl provides a default built-in write function that writes received data to stdout. Set the CURLOPT_WRITEFUNCTION to receive the data, or possibly set CURLOPT_WRITEDATA to a different FILE * handle.

5.11 How do I make libcurl not receive the whole HTTP response?

You make the write callback (or progress callback) return an error and libcurl will then abort the transfer.

5.12 Can I make libcurl fake or hide my real IP address?

No. libcurl operates on a higher level. Besides, faking IP address would imply sending IP packet with a made-up source address, and then you normally get a problem with receiving the packet sent back as they would then not be routed to you!

If you use a proxy to access remote sites, the sites will not see your local IP address but instead the address of the proxy.

Also note that on many networks NATs or other IP-munging techniques are used that makes you see and use a different IP address locally than what the remote server will see you coming from. You may also consider using https://www.torproject.org/ .

5.13 How do I stop an ongoing transfer?

With the easy interface you make sure to return the correct error code from one of the callbacks, but none of them are instant. There is no function you can call from another thread or similar that will stop it immediately. Instead, you need to make sure that one of the callbacks you use returns an appropriate value that will stop the transfer. Suitable callbacks that you can do this with include the progress callback, the read callback and the write callback.

If you're using the multi interface, you can also stop a transfer by removing the particular easy handle from the multi stack at any moment you think the transfer is done or when you wish to abort the transfer.

5.14 Using C++ non-static functions for callbacks?

libcurl is a C library, it doesn't know anything about C++ member functions.

You can overcome this "limitation" with a relative ease using a static member function that is passed a pointer to the class:

// f is the pointer to your object.
static YourClass::func(void buffer, size_t sz, size_t n, void f)
{
// Call non-static member function.
static_cast(f)->nonStaticFunction();
}
// This is how you pass pointer to the static function:
curl_easy_setopt(hcurl, CURLOPT_WRITEFUNCTION, YourClass:func);
curl_easy_setopt(hcurl, CURLOPT_WRITEDATA, this);
5.15 How do I get an FTP directory listing?

If you end the FTP URL you request with a slash, libcurl will provide you with a directory listing of that given directory. You can also set CURLOPT_CUSTOMREQUEST to alter what exact listing command libcurl would use to list the files.

The follow-up question that tend to follow the previous one, is how a program is supposed to parse the directory listing. How does it know what's a file and what's a dir and what's a symlink etc. The harsh reality is that FTP provides no such fine and easy-to-parse output. The output format FTP servers respond to LIST commands are entirely at the server's own liking and the NLST output doesn't reveal any types and in many cases don't even include all the directory entries. Also, both LIST and NLST tend to hide unix-style hidden files (those that start with a dot) by default so you need to do "LIST -a" or similar to see them.

The application thus needs to parse the LIST output. One such existing list parser is available at https://cr.yp.to/ftpparse.html Versions of libcurl since 7.21.0 also provide the ability to specify a wildcard to download multiple files from one FTP directory.

5.16 I want a different time-out!

Time and time again users realize that CURLOPT_TIMEOUT and CURLOPT_CONNECTIMEOUT are not sufficiently advanced or flexible to cover all the various use cases and scenarios applications end up with.

libcurl offers many more ways to time-out operations. A common alternative is to use the CURLOPT_LOW_SPEED_LIMIT and CURLOPT_LOW_SPEED_TIME options to specify the lowest possible speed to accept before to consider the transfer timed out.

The most flexible way is by writing your own time-out logic and using CURLOPT_PROGRESSFUNCTION (perhaps in combination with other callbacks) and use that to figure out exactly when the right condition is met when the transfer should get stopped.

5.17 Can I write a server with libcurl?

No. libcurl offers no functions or building blocks to build any kind of internet protocol server. libcurl is only a client-side library. For server libraries, you need to continue your search elsewhere but there exist many good open source ones out there for most protocols you could possibly want a server for. And there are really good stand-alone ones that have been tested and proven for many years. There's no need for you to reinvent them!

5.18 Does libcurl use threads?

Put simply: no, libcurl will execute in the same thread you call it in. All callbacks will be called in the same thread as the one you call libcurl in.

If you want to avoid your thread to be blocked by the libcurl call, you make sure you use the non-blocking API which will do transfers asynchronously - but still in the same single thread.

libcurl will potentially internally use threads for name resolving, if it was built to work like that, but in those cases it'll create the child threads by itself and they will only be used and then killed internally by libcurl and never exposed to the outside.

  1. License Issues

Curl and libcurl are released under a MIT/X derivate license. The license is very liberal and should not impose a problem for your project. This section is just a brief summary for the cases we get the most questions. (Parts of this section was much enhanced by Bjorn Reese.)

We are not lawyers and this is not legal advice. You should probably consult one if you want true and accurate legal insights without our prejudice. Note especially that this section concerns the libcurl license only; compiling in features of libcurl that depend on other libraries (e.g. OpenSSL) may affect the licensing obligations of your application.

6.1 I have a GPL program, can I use the libcurl library?

Yes!

Since libcurl may be distributed under the MIT/X derivate license, it can be used together with GPL in any software.

6.2 I have a closed-source program, can I use the libcurl library?

Yes!

libcurl does not put any restrictions on the program that uses the library.

6.3 I have a BSD licensed program, can I use the libcurl library?

Yes!

libcurl does not put any restrictions on the program that uses the library.

6.4 I have a program that uses LGPL libraries, can I use libcurl?

Yes!

The LGPL license doesn't clash with other licenses.

6.5 Can I modify curl/libcurl for my program and keep the changes secret?

Yes!

The MIT/X derivate license practically allows you to do almost anything with the sources, on the condition that the copyright texts in the sources are left intact.

6.6 Can you please change the curl/libcurl license to XXXX?

No.

We have carefully picked this license after years of development and discussions and a large amount of people have contributed with source code knowing that this is the license we use. This license puts the restrictions we want on curl/libcurl and it does not spread to other programs or libraries that use it. It should be possible for everyone to use libcurl or curl in their projects, no matter what license they already have in use.

6.7 What are my obligations when using libcurl in my commercial apps?

Next to none. All you need to adhere to is the MIT-style license (stated in the COPYING file) which basically says you have to include the copyright notice in "all copies" and that you may not use the copyright holder's name when promoting your software.

You do not have to release any of your source code.

You do not have to reveal or make public any changes to the libcurl source code.

You do not have to broadcast to the world that you are using libcurl within your app.

All we ask is that you disclose "the copyright notice and this permission notice" somewhere. Most probably like in the documentation or in the section where other third party dependencies already are mentioned and acknowledged.

As can be seen here: https://curl.haxx.se/docs/companies.html and elsewhere, more and more companies are discovering the power of libcurl and take advantage of it even in commercial environments.

  1. PHP/CURL Issues

7.1 What is PHP/CURL?

The module for PHP that makes it possible for PHP programs to access curl- functions from within PHP.

In the cURL project we call this module PHP/CURL to differentiate it from curl the command line tool and libcurl the library. The PHP team however does not refer to it like this (for unknown reasons). They call it plain CURL (often using all caps) or sometimes ext/curl, but both cause much confusion to users which in turn gives us a higher question load.

7.2 Who wrote PHP/CURL?

PHP/CURL was initially written by Sterling Hughes.

7.3 Can I perform multiple requests using the same handle?

Yes - at least in PHP version 4.3.8 and later (this has been known to not work in earlier versions, but the exact version when it started to work is unknown to me).

After a transfer, you just set new options in the handle and make another transfer. This will make libcurl re-use the same connection if it can.

7.4 Does PHP/CURL have dependencies?

PHP/CURL is a module that comes with the regular PHP package. It depends on and uses libcurl, so you need to have libcurl installed properly before PHP/CURL can be used.

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达到什么标准才能称为“健康的老年人”?

on May 20, 2016

进入老年的身体变化

一是体表形态的改变,须发变白、稀疏,皮肤变薄出现皱纹,牙龈萎缩,牙齿松动脱落,耳垂逐渐延长,骨骼肌的萎缩等,都是正常变化。

二是器官功能的下降,视、听功能下降,心脏的搏出量减少为年轻时的一半左右,肺活量减少50%~60%、肾脏的清除能力减少40%~50%。脑组织的改变,例如脑组织萎缩、脑回的变宽,神经细胞的减少,这个主要表现在大脑的供氧量降低和脑血管的阻力增加,这带来记忆力下降,头晕等问题。

三是机体的调控能力下降,学习、运动的反应速度下降,另外免疫的防御能力和监视能力下降,这就是为什么老年人容易发生多种感染性疾病,或者恶性疾病的原因。

衰老算不算疾病?

衰老并不是一种疾病,而是生命的必然过程,衰老导致功能减退,从而导致各种疾病的发生。但老年人常常把机体功能减退当成一种病态,这是认识上的误区。其实,衰老受到多种内、外因素的影响,比如生活环境、个人习惯、遗传因素等。老年人在功能衰退的过程中,只有一部分会导致疾病的发生。

人人都会老,那么什么样的老年人才算健康的老年人?

老年人健康的内涵是什么?

世界卫生组织将健康定义为:人的健康是躯体、精神和社会生活的完好状态,不仅仅是没有疾病或不虚弱。用十六个字概括一下就是:无病无弱、身心健全、社会适应、环境和谐。

对于健康老年人,中华医学会也给出了一个标准供大家参考:

1,躯体无明显的畸形,无明显的驼背等不良体形;

2,神经系统基本正常,无偏瘫,老年人无痴呆,或者其他神经系统疾病;

3,心脏的基本功能正常,无高血压、冠心病及其他的器质性的心脏病;

4,无明显的肺功能下降或者不全,包括慢性的肺部疾病;

5,无肝硬化、肾脏疾病及恶性肿瘤。

“五好”老人

老年人可以从以下几个方面初步评价自己的健康状态,简称“五好”老人:

第一,胃口好;

第二,大小便好,大小便是人体健康的一个重要的指标!

第三,睡眠好;

第四,思维好;

第五,腿脚好。

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健康生活守则:“十不过” 最好背下来

on May 18, 2016

健康长寿是每个人的心愿,做到下面这“十不过”,祝您长命百岁!

1衣不过暖
穿衣戴帽不要过于暖和,也不可以过于单薄,过暖容易感冒,过冷容易受寒。

2食不过饱
吃饭吃七八分饱,粗细搭配,荤素相兼。饭前要喝汤,不吸烟,不喝酒。

3住不过奢
生活要随遇而安,居室干净舒适即可。不要太过富丽堂皇,那样对个人心态不好。

4行不过富
身体健康允许,尽量以步代车。若是出门必乘车,时间长了,腿脚就会不那么灵便。

5劳不过累
劳动的强度是有限度的,超过负荷量会造成身体的伤害。要注意劳逸结合,适当休息。

6逸不过安
终日无所事事,会丧失对生活的情趣,而心灰意懒。所以,平时可以多参加活动,比如散步聊天、写字作画、下棋看戏、读书看报等。勤于动脑,保持心情舒畅,以延年增寿。

7喜不过欢
人逢喜事精神爽,但喜不能过头,过喜则伤心。古人范进中举之后发疯,即为过喜所致。

8 怒不过暴
心里有烦恼,千万不要生怒气,怒会伤肝。要学会控制自己的情绪,提高涵养,乐观处世。

9名不过求
名利皆身外之物,生不带来,死不带去。名利只是过眼烟云,不要过分追求。

10利不过贪
“酒色财气”我不取,“风花雪月”不沾边。如果能做到无欲无求、无牵无挂、知足常乐、顺其自然,那么就能耄耋无忧。

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Wget 1.17.1

on May 11, 2016

GNU Wget 1.17.1
The non-interactive download utility
Updated for Wget 1.17.1, 10 December 2015
by Hrvoje Nikˇ si´ c and others
This file documents the GNU Wget utility for downloading network data.
Copyright c ? 1996, 1997, 1998, 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, 2008, 2009,
2010, 2011, 2015 Free Software Foundation, Inc.
Permission is granted to make and distribute verbatim copies of this manual provided the copy-
right notice and this permission notice are preserved on all copies.
Permission is granted to copy, distribute and/or modify this document under the terms of
the GNU Free Documentation License, Version 1.3 or any later version published by the Free
Software Foundation; with no Invariant Sections, with no Front-Cover Texts, and with no Back-
Cover Texts. A copy of the license is included in the section entitled “GNU Free Documentation
License”.
i
Table of Contents
Chapter 1: Overview 1
1 Overview
GNU Wget is a free utility for non-interactive download of files from the Web. It supports http,
https, and ftp protocols, as well as retrieval through http proxies.
This chapter is a partial overview of Wget’s features.
• Wget is non-interactive, meaning that it can work in the background, while the user is not
logged on. This allows you to start a retrieval and disconnect from the system, letting Wget
finish the work. By contrast, most of the Web browsers require constant user’s presence,
which can be a great hindrance when transferring a lot of data.
• Wget can follow links in html, xhtml, and css pages, to create local versions of remote web
sites, fully recreating the directory structure of the original site. This is sometimes referred
to as “recursive downloading.” While doing that, Wget respects the Robot Exclusion
Standard (‘/robots.txt’). Wget can be instructed to convert the links in downloaded files
to point at the local files, for offline viewing.
• File name wildcard matching and recursive mirroring of directories are available when re-
trieving via ftp. Wget can read the time-stamp information given by both http and ftp
servers, and store it locally. Thus Wget can see if the remote file has changed since last
retrieval, and automatically retrieve the new version if it has. This makes Wget suitable
for mirroring of ftp sites, as well as home pages.
• Wget has been designed for robustness over slow or unstable network connections; if a
download fails due to a network problem, it will keep retrying until the whole file has
been retrieved. If the server supports regetting, it will instruct the server to continue the
download from where it left off.
• Wget supports proxy servers, which can lighten the network load, speed up retrieval and
provide access behind firewalls. Wget uses the passive ftp downloading by default, active
ftp being an option.
• Wget supports IP version 6, the next generation of IP. IPv6 is autodetected at compile-time,
and can be disabled at either build or run time. Binaries built with IPv6 support work well
in both IPv4-only and dual family environments.
• Built-in features offer mechanisms to tune which links you wish to follow (see hundefinedi
[Following Links], page hundefinedi).
• The progress of individual downloads is traced using a progress gauge. Interactive downloads
are tracked using a “thermometer”-style gauge, whereas non-interactive ones are traced with
dots, each dot representing a fixed amount of data received (1KB by default). Either gauge
can be customized to your preferences.
• Most of the features are fully configurable, either through command line options, or via the
initialization file ‘.wgetrc’ (see hundefinedi [Startup File], page hundefinedi). Wget allows
you to define global startup files (‘/usr/local/etc/wgetrc’ by default) for site settings.
You can also specify the location of a startup file with the –config option.
• Finally, GNU Wget is free software. This means that everyone may use it, redistribute it
and/or modify it under the terms of the GNU General Public License, as published by the
Free Software Foundation (see the file ‘COPYING’ that came with GNU Wget, for details).
Chapter 2: Invoking 2
2 Invoking
By default, Wget is very simple to invoke. The basic syntax is:
wget [option]... [URL]...
Wget will simply download all the urls specified on the command line. URL is a Uniform
Resource Locator, as defined below.
However, you may wish to change some of the default parameters of Wget. You can do it
two ways: permanently, adding the appropriate command to ‘.wgetrc’ (see hundefinedi [Startup
File], page hundefinedi), or specifying it on the command line.
2.1 URL Format
URL is an acronym for Uniform Resource Locator. A uniform resource locator is a compact
string representation for a resource available via the Internet. Wget recognizes the url syntax
as per rfc1738. This is the most widely used form (square brackets denote optional parts):
http://host[:port]/directory/file
ftp://host[:port]/directory/file
You can also encode your username and password within a url:
ftp://user:password@host/path
http://user:password@host/path
Either user or password, or both, may be left out. If you leave out either the http username
or password, no authentication will be sent. If you leave out the ftp username, ‘anonymous’
will be used. If you leave out the ftp password, your email address will be supplied as a default
password. 1
Important Note: if you specify a password-containing url on the command line, the user-
name and password will be plainly visible to all users on the system, by way of ps. On multi-user
systems, this is a big security risk. To work around it, use wget -i - and feed the urls to Wget’s
standard input, each on a separate line, terminated by C-d.
You can encode unsafe characters in a url as ‘%xy’, xy being the hexadecimal representation
of the character’s ascii value. Some common unsafe characters include ‘%’ (quoted as ‘%25’),
‘:’ (quoted as ‘%3A’), and ‘@’ (quoted as ‘%40’). Refer to rfc1738 for a comprehensive list of
unsafe characters.
Wget also supports the type feature for ftp urls. By default, ftp documents are retrieved
in the binary mode (type ‘i’), which means that they are downloaded unchanged. Another
useful mode is the ‘a’ (ASCII) mode, which converts the line delimiters between the different
operating systems, and is thus useful for text files. Here is an example:
ftp://host/directory/file;type=a
Two alternative variants of url specification are also supported, because of historical (hys-
terical?) reasons and their widespreaded use.
ftp-only syntax (supported by NcFTP):
host:/dir/file
http-only syntax (introduced by Netscape):
host[:port]/dir/file
These two alternative forms are deprecated, and may cease being supported in the future.
If you do not understand the difference between these notations, or do not know which one
to use, just use the plain ordinary format you use with your favorite browser, like Lynx or
Netscape.
1
If you have a ‘.netrc’ file in your home directory, password will also be searched for there.
Chapter 2: Invoking 3
2.2 Option Syntax
Since Wget uses GNU getopt to process command-line arguments, every option has a long form
along with the short one. Long options are more convenient to remember, but take time to type.
You may freely mix different option styles, or specify options after the command-line arguments.
Thus you may write:
wget -r --tries=10 http://fly.srk.fer.hr/ -o log
The space between the option accepting an argument and the argument may be omitted.
Instead of ‘-o log’ you can write ‘-olog’.
You may put several options that do not require arguments together, like:
wget -drc URL
This is completely equivalent to:
wget -d -r -c URL
Since the options can be specified after the arguments, you may terminate them with ‘--’.
So the following will try to download url ‘-x’, reporting failure to ‘log’:
wget -o log -- -x
The options that accept comma-separated lists all respect the convention that specifying an
empty list clears its value. This can be useful to clear the ‘.wgetrc’ settings. For instance, if
your ‘.wgetrc’ sets exclude_directories to ‘/cgi-bin’, the following example will first reset
it, and then set it to exclude ‘/~nobody’ and ‘/~somebody’. You can also clear the lists in
‘.wgetrc’ (see hundefinedi [Wgetrc Syntax], page hundefinedi).
wget -X ’’ -X /~nobody,/~somebody
Most options that do not accept arguments are boolean options, so named because their state
can be captured with a yes-or-no (“boolean”) variable. For example, ‘--follow-ftp’ tells Wget
to follow FTP links from HTML files and, on the other hand, ‘--no-glob’ tells it not to perform
file globbing on FTP URLs. A boolean option is either affirmative or negative (beginning with
‘--no’). All such options share several properties.
Unless stated otherwise, it is assumed that the default behavior is the opposite of what the
option accomplishes. For example, the documented existence of ‘--follow-ftp’ assumes that
the default is to not follow FTP links from HTML pages.
Affirmative options can be negated by prepending the ‘--no-’ to the option name; negative
options can be negated by omitting the ‘--no-’ prefix. This might seem superfluous—if the
default for an affirmative option is to not do something, then why provide a way to explicitly
turn it off? But the startup file may in fact change the default. For instance, using follow_ftp
= on in ‘.wgetrc’ makes Wget follow FTP links by default, and using ‘--no-follow-ftp’ is the
only way to restore the factory default from the command line.
2.3 Basic Startup Options
‘-V’
‘--version’
Display the version of Wget.
‘-h’
‘--help’ Print a help message describing all of Wget’s command-line options.
‘-b’
‘--background’
Go to background immediately after startup. If no output file is specified via the
‘-o’, output is redirected to ‘wget-log’.
Chapter 2: Invoking 4
‘-e command’
‘--execute command’
Execute command as if it were a part of ‘.wgetrc’ (see hundefinedi [Startup File],
page hundefinedi). A command thus invoked will be executed after the commands
in ‘.wgetrc’, thus taking precedence over them. If you need to specify more than
one wgetrc command, use multiple instances of ‘-e’.
2.4 Logging and Input File Options
‘-o logfile’
‘--output-file=logfile’
Log all messages to logfile. The messages are normally reported to standard error.
‘-a logfile’
‘--append-output=logfile’
Append to logfile. This is the same as ‘-o’, only it appends to logfile instead of
overwriting the old log file. If logfile does not exist, a new file is created.
‘-d’
‘--debug’ Turn on debug output, meaning various information important to the developers of
Wget if it does not work properly. Your system administrator may have chosen to
compile Wget without debug support, in which case ‘-d’ will not work. Please note
that compiling with debug support is always safe—Wget compiled with the debug
support will not print any debug info unless requested with ‘-d’. See hundefinedi
[Reporting Bugs], page hundefinedi, for more information on how to use ‘-d’ for
sending bug reports.
‘-q’
‘--quiet’ Turn off Wget’s output.
‘-v’
‘--verbose’
Turn on verbose output, with all the available data. The default output is verbose.
‘-nv’
‘--no-verbose’
Turn off verbose without being completely quiet (use ‘-q’ for that), which means
that error messages and basic information still get printed.
‘--report-speed=type’
Output bandwidth as type. The only accepted value is ‘bits’.
‘-i file’
‘--input-file=file’
Read urls from a local or external file. If ‘-’ is specified as file, urls are read from
the standard input. (Use ‘./-’ to read from a file literally named ‘-’.)
If this function is used, no urls need be present on the command line. If there are
urls both on the command line and in an input file, those on the command lines
will be the first ones to be retrieved. If ‘--force-html’ is not specified, then file
should consist of a series of URLs, one per line.
However, if you specify ‘--force-html’, the document will be regarded as ‘html’.
In that case you may have problems with relative links, which you can solve either
by adding to the documents or by specifying ‘--base=url’ on
the command line.
Chapter 2: Invoking 5
If the file is an external one, the document will be automatically treated as ‘html’
if the Content-Type matches ‘text/html’. Furthermore, the file’s location will be
implicitly used as base href if none was specified.
‘--input-metalink=file’
Downloads files covered in local Metalink file. Metalink version 3 and 4 are sup-
ported.
‘--metalink-over-http’
Issues HTTP HEAD request instead of GET and extracts Metalink metadata from
response headers. Then it switches to Metalink download. If no valid Metalink
metadata is found, it falls back to ordinary HTTP download.
‘--preferred-location’
Set preferred location for Metalink resources. This has effect if multiple resources
with same priority are available.
‘-F’
‘--force-html’
When input is read from a file, force it to be treated as an html file. This enables
you to retrieve relative links from existing html files on your local disk, by adding

to html, or using the ‘--base’ command-line option.
‘-B URL’
‘--base=URL’
Resolves relative links using URL as the point of reference, when reading links
from an HTML file specified via the ‘-i’/‘--input-file’ option (together with
‘--force-html’, or when the input file was fetched remotely from a server describing
it as html). This is equivalent to the presence of a BASE tag in the html input file,
with URL as the value for the href attribute.
For instance, if you specify ‘http://foo/bar/a.html’ for URL, and
Wget reads ‘../baz/b.html’ from the input file, it would be resolved to
http://foo/baz/b.html’.
‘--config=FILE’
Specify the location of a startup file you wish to use.
‘--rejected-log=logfile’
Logs all URL rejections to logfile as comma separated values. The values include
the reason of rejection, the URL and the parent URL it was found in.
2.5 Download Options
‘--bind-address=ADDRESS’
When making client TCP/IP connections, bind to ADDRESS on the local machine.
ADDRESS may be specified as a hostname or IP address. This option can be useful
if your machine is bound to multiple IPs.
‘-t number’
‘--tries=number’
Set number of tries to number. Specify 0 or ‘inf’ for infinite retrying. The default
is to retry 20 times, with the exception of fatal errors like “connection refused” or
“not found” (404), which are not retried.
‘-O file’
‘--output-document=file’
The documents will not be written to the appropriate files, but all will be concate-
nated together and written to file. If ‘-’ is used as file, documents will be printed
Chapter 2: Invoking 6
to standard output, disabling link conversion. (Use ‘./-’ to print to a file literally
named ‘-’.)
Use of ‘-O’ is not intended to mean simply “use the name file instead of the one in
the URL;” rather, it is analogous to shell redirection: ‘wget -O file http://foo’
is intended to work like ‘wget -O - http://foo > file’; ‘file’ will be truncated
immediately, and all downloaded content will be written there.
For this reason, ‘-N’ (for timestamp-checking) is not supported in combination with
‘-O’: since file is always newly created, it will always have a very new timestamp.
A warning will be issued if this combination is used.
Similarly, using ‘-r’ or ‘-p’ with ‘-O’ may not work as you expect: Wget won’t just
download the first file to file and then download the rest to their normal names: all
downloaded content will be placed in file. This was disabled in version 1.11, but
has been reinstated (with a warning) in 1.11.2, as there are some cases where this
behavior can actually have some use.
A combination with ‘-nc’ is only accepted if the given output file does not exist.
Note that a combination with ‘-k’ is only permitted when downloading a single
document, as in that case it will just convert all relative URIs to external ones; ‘-k’
makes no sense for multiple URIs when they’re all being downloaded to a single file;
‘-k’ can be used only when the output is a regular file.
‘-nc’
‘--no-clobber’
If a file is downloaded more than once in the same directory, Wget’s behavior de-
pends on a few options, including ‘-nc’. In certain cases, the local file will be
clobbered, or overwritten, upon repeated download. In other cases it will be pre-
served.
When running Wget without ‘-N’, ‘-nc’, ‘-r’, or ‘-p’, downloading the same file in
the same directory will result in the original copy of file being preserved and the
second copy being named ‘file.1’. If that file is downloaded yet again, the third
copy will be named ‘file.2’, and so on. (This is also the behavior with ‘-nd’, even
if ‘-r’ or ‘-p’ are in effect.) When ‘-nc’ is specified, this behavior is suppressed,
and Wget will refuse to download newer copies of ‘file’. Therefore, “no-clobber”
is actually a misnomer in this mode—it’s not clobbering that’s prevented (as the
numeric suffixes were already preventing clobbering), but rather the multiple version
saving that’s prevented.
When running Wget with ‘-r’ or ‘-p’, but without ‘-N’, ‘-nd’, or ‘-nc’, re-
downloading a file will result in the new copy simply overwriting the old. Adding
‘-nc’ will prevent this behavior, instead causing the original version to be preserved
and any newer copies on the server to be ignored.
When running Wget with ‘-N’, with or without ‘-r’ or ‘-p’, the decision as to
whether or not to download a newer copy of a file depends on the local and remote
timestamp and size of the file (see hundefinedi [Time-Stamping], page hundefinedi).
‘-nc’ may not be specified at the same time as ‘-N’.
A combination with ‘-O’/‘--output-document’ is only accepted if the given output
file does not exist.
Note that when ‘-nc’ is specified, files with the suffixes ‘.html’ or ‘.htm’ will be
loaded from the local disk and parsed as if they had been retrieved from the Web.
Chapter 2: Invoking 7
‘--backups=backups’
Before (over)writing a file, back up an existing file by adding a ‘.1’ suffix (‘_1’ on
VMS) to the file name. Such backup files are rotated to ‘.2’, ‘.3’, and so on, up to
backups (and lost beyond that).
‘-c’
‘--continue’
Continue getting a partially-downloaded file. This is useful when you want to finish
up a download started by a previous instance of Wget, or by another program. For
instance:
wget -c ftp://sunsite.doc.ic.ac.uk/ls-lR.Z
If there is a file named ‘ls-lR.Z’ in the current directory, Wget will assume that it
is the first portion of the remote file, and will ask the server to continue the retrieval
from an offset equal to the length of the local file.
Note that you don’t need to specify this option if you just want the current invocation
of Wget to retry downloading a file should the connection be lost midway through.
This is the default behavior. ‘-c’ only affects resumption of downloads started prior
to this invocation of Wget, and whose local files are still sitting around.
Without ‘-c’, the previous example would just download the remote file to
‘ls-lR.Z.1’, leaving the truncated ‘ls-lR.Z’ file alone.
Beginning with Wget 1.7, if you use ‘-c’ on a non-empty file, and it turns out that
the server does not support continued downloading, Wget will refuse to start the
download from scratch, which would effectively ruin existing contents. If you really
want the download to start from scratch, remove the file.
Also beginning with Wget 1.7, if you use ‘-c’ on a file which is of equal size as
the one on the server, Wget will refuse to download the file and print an explana-
tory message. The same happens when the file is smaller on the server than lo-
cally (presumably because it was changed on the server since your last download
attempt)—because “continuing” is not meaningful, no download occurs.
On the other side of the coin, while using ‘-c’, any file that’s bigger on the server
than locally will be considered an incomplete download and only (length(remote)

  • length(local)) bytes will be downloaded and tacked onto the end of the local
    file. This behavior can be desirable in certain cases—for instance, you can use ‘wget
    -c’ to download just the new portion that’s been appended to a data collection or
    log file.
    However, if the file is bigger on the server because it’s been changed, as opposed to
    just appended to, you’ll end up with a garbled file. Wget has no way of verifying
    that the local file is really a valid prefix of the remote file. You need to be especially
    careful of this when using ‘-c’ in conjunction with ‘-r’, since every file will be
    considered as an "incomplete download" candidate.
    Another instance where you’ll get a garbled file if you try to use ‘-c’ is if you have
    a lame http proxy that inserts a “transfer interrupted” string into the local file. In
    the future a “rollback” option may be added to deal with this case.
    Note that ‘-c’ only works with ftp servers and with http servers that support the
    Range header.
    ‘--start-pos=OFFSET’
    Start downloading at zero-based position OFFSET. Offset may be expressed in
    bytes, kilobytes with the ‘k’ suffix, or megabytes with the ‘m’ suffix, etc.
    Chapter 2: Invoking 8
    ‘--start-pos’ has higher precedence over ‘--continue’. When ‘--start-pos’
    and ‘--continue’ are both specified, wget will emit a warning then proceed as
    if ‘--continue’ was absent.
    Server support for continued download is required, otherwise ‘--start-pos’ cannot
    help. See ‘-c’ for details.
    ‘--progress=type’
    Select the type of the progress indicator you wish to use. Legal indicators are “dot”
    and “bar”.
    The “bar” indicator is used by default. It draws an ascii progress bar graphics
    (a.k.a “thermometer” display) indicating the status of retrieval. If the output is not
    a TTY, the “dot” bar will be used by default.
    Use ‘--progress=dot’ to switch to the “dot” display. It traces the retrieval by
    printing dots on the screen, each dot representing a fixed amount of downloaded
    data.
    The progress type can also take one or more parameters. The parameters vary based
    on the type selected. Parameters to type are passed by appending them to the type
    sperated by a colon (:) like this: ‘--progress=type:parameter1:parameter2’.
    When using the dotted retrieval, you may set the style by specifying the type as
    ‘dot:style’. Different styles assign different meaning to one dot. With the default
    style each dot represents 1K, there are ten dots in a cluster and 50 dots in a line.
    The binary style has a more “computer”-like orientation—8K dots, 16-dots clusters
    and 48 dots per line (which makes for 384K lines). The mega style is suitable for
    downloading large files—each dot represents 64K retrieved, there are eight dots in
    a cluster, and 48 dots on each line (so each line contains 3M). If mega is not enough
    then you can use the giga style—each dot represents 1M retrieved, there are eight
    dots in a cluster, and 32 dots on each line (so each line contains 32M).
    With ‘--progress=bar’, there are currently two possible parameters, force and
    noscroll.
    When the output is not a TTY, the progress bar always falls back to “dot”, even
    if ‘--progress=bar’ was passed to Wget during invokation. This behaviour can
    be overridden and the “bar” output forced by using the “force” parameter as
    ‘--progress=bar:force’.
    By default, the ‘bar’ style progress bar scroll the name of the file from left to right
    for the file being downloaded if the filename exceeds the maximum length allotted
    for its display. In certain cases, such as with ‘--progress=bar:force’, one may not
    want the scrolling filename in the progress bar. By passing the “noscroll” parameter,
    Wget can be forced to display as much of the filename as possible without scrolling
    through it.
    Note that you can set the default style using the progress command in ‘.wgetrc’.
    That setting may be overridden from the command line. For example, to force the
    bar output without scrolling, use ‘--progress=bar:force:noscroll’.
    ‘--show-progress’
    Force wget to display the progress bar in any verbosity.
    By default, wget only displays the progress bar in verbose mode. One may however,
    want wget to display the progress bar on screen in conjunction with any other
    verbosity modes like ‘--no-verbose’ or ‘--quiet’. This is often a desired a property
    when invoking wget to download several small/large files. In such a case, wget could
    simply be invoked with this parameter to get a much cleaner output on the screen.
    Chapter 2: Invoking 9
    This option will also force the progress bar to be printed to ‘stderr’ when used
    alongside the ‘--logfile’ option.
    ‘-N’
    ‘--timestamping’
    Turn on time-stamping. See hundefinedi [Time-Stamping], page hundefinedi, for
    details.
    ‘--no-if-modified-since’
    Do not send If-Modified-Since header in ‘-N’ mode. Send preliminary HEAD request
    instead. This has only effect in ‘-N’ mode.
    ‘--no-use-server-timestamps’
    Don’t set the local file’s timestamp by the one on the server.
    By default, when a file is downloaded, its timestamps are set to match those from
    the remote file. This allows the use of ‘--timestamping’ on subsequent invocations
    of wget. However, it is sometimes useful to base the local file’s timestamp on when
    it was actually downloaded; for that purpose, the ‘--no-use-server-timestamps’
    option has been provided.
    ‘-S’
    ‘--server-response’
    Print the headers sent by http servers and responses sent by ftp servers.
    ‘--spider’
    When invoked with this option, Wget will behave as a Web spider, which means
    that it will not download the pages, just check that they are there. For example,
    you can use Wget to check your bookmarks:
    wget --spider --force-html -i bookmarks.html
    This feature needs much more work for Wget to get close to the functionality of real
    web spiders.
    ‘-T seconds’
    ‘--timeout=seconds’
    Set the network timeout to seconds seconds. This is equivalent to specifying
    ‘--dns-timeout’, ‘--connect-timeout’, and ‘--read-timeout’, all at the same
    time.
    When interacting with the network, Wget can check for timeout and abort the
    operation if it takes too long. This prevents anomalies like hanging reads and infinite
    connects. The only timeout enabled by default is a 900-second read timeout. Setting
    a timeout to 0 disables it altogether. Unless you know what you are doing, it is best
    not to change the default timeout settings.
    All timeout-related options accept decimal values, as well as subsecond values. For
    example, ‘0.1’ seconds is a legal (though unwise) choice of timeout. Subsecond
    timeouts are useful for checking server response times or for testing network latency.
    ‘--dns-timeout=seconds’
    Set the DNS lookup timeout to seconds seconds. DNS lookups that don’t complete
    within the specified time will fail. By default, there is no timeout on DNS lookups,
    other than that implemented by system libraries.
    ‘--connect-timeout=seconds’
    Set the connect timeout to seconds seconds. TCP connections that take longer to
    establish will be aborted. By default, there is no connect timeout, other than that
    implemented by system libraries.
    Chapter 2: Invoking 10
    ‘--read-timeout=seconds’
    Set the read (and write) timeout to seconds seconds. The “time” of this timeout
    refers to idle time: if, at any point in the download, no data is received for more
    than the specified number of seconds, reading fails and the download is restarted.
    This option does not directly affect the duration of the entire download.
    Of course, the remote server may choose to terminate the connection sooner than
    this option requires. The default read timeout is 900 seconds.
    ‘--limit-rate=amount’
    Limit the download speed to amount bytes per second. Amount may be expressed
    in bytes, kilobytes with the ‘k’ suffix, or megabytes with the ‘m’ suffix. For example,
    ‘--limit-rate=20k’ will limit the retrieval rate to 20KB/s. This is useful when, for
    whatever reason, you don’t want Wget to consume the entire available bandwidth.
    This option allows the use of decimal numbers, usually in conjunction with power
    suffixes; for example, ‘--limit-rate=2.5k’ is a legal value.
    Note that Wget implements the limiting by sleeping the appropriate amount of time
    after a network read that took less time than specified by the rate. Eventually this
    strategy causes the TCP transfer to slow down to approximately the specified rate.
    However, it may take some time for this balance to be achieved, so don’t be surprised
    if limiting the rate doesn’t work well with very small files.
    ‘-w seconds’
    ‘--wait=seconds’
    Wait the specified number of seconds between the retrievals. Use of this option is
    recommended, as it lightens the server load by making the requests less frequent.
    Instead of in seconds, the time can be specified in minutes using the m suffix, in
    hours using h suffix, or in days using d suffix.
    Specifying a large value for this option is useful if the network or the destination
    host is down, so that Wget can wait long enough to reasonably expect the network
    error to be fixed before the retry. The waiting interval specified by this function is
    influenced by --random-wait, which see.
    ‘--waitretry=seconds’
    If you don’t want Wget to wait between every retrieval, but only between retries of
    failed downloads, you can use this option. Wget will use linear backoff, waiting 1
    second after the first failure on a given file, then waiting 2 seconds after the second
    failure on that file, up to the maximum number of seconds you specify.
    By default, Wget will assume a value of 10 seconds.
    ‘--random-wait’
    Some web sites may perform log analysis to identify retrieval programs such as Wget
    by looking for statistically significant similarities in the time between requests. This
    option causes the time between requests to vary between 0.5 and 1.5 wait seconds,
    where wait was specified using the ‘--wait’ option, in order to mask Wget’s presence
    from such analysis.
    A 2001 article in a publication devoted to development on a popular consumer
    platform provided code to perform this analysis on the fly. Its author suggested
    blocking at the class C address level to ensure automated retrieval programs were
    blocked despite changing DHCP-supplied addresses.
    The ‘--random-wait’ option was inspired by this ill-advised recommendation to
    block many unrelated users from a web site due to the actions of one.
    ‘--no-proxy’
    Don’t use proxies, even if the appropriate
    _proxy environment variable is defined.
    Chapter 2: Invoking 11
    See hundefinedi [Proxies], page hundefinedi, for more information about the use of
    proxies with Wget.
    ‘-Q quota’
    ‘--quota=quota’
    Specify download quota for automatic retrievals. The value can be specified in bytes
    (default), kilobytes (with ‘k’ suffix), or megabytes (with ‘m’ suffix).
    Note that quota will never affect downloading a single file. So if you specify ‘wget
    -Q10k ftp://wuarchive.wustl.edu/ls-lR.gz’, all of the ‘ls-lR.gz’ will be down-
    loaded. The same goes even when several urls are specified on the command-line.
    However, quota is respected when retrieving either recursively, or from an input file.
    Thus you may safely type ‘wget -Q2m -i sites’—download will be aborted when
    the quota is exceeded.
    Setting quota to 0 or to ‘inf’ unlimits the download quota.
    ‘--no-dns-cache’
    Turn off caching of DNS lookups. Normally, Wget remembers the IP addresses it
    looked up from DNS so it doesn’t have to repeatedly contact the DNS server for the
    same (typically small) set of hosts it retrieves from. This cache exists in memory
    only; a new Wget run will contact DNS again.
    However, it has been reported that in some situations it is not desirable to cache host
    names, even for the duration of a short-running application like Wget. With this
    option Wget issues a new DNS lookup (more precisely, a new call to gethostbyname
    or getaddrinfo) each time it makes a new connection. Please note that this option
    will not affect caching that might be performed by the resolving library or by an
    external caching layer, such as NSCD.
    If you don’t understand exactly what this option does, you probably won’t need it.
    ‘--restrict-file-names=modes’
    Change which characters found in remote URLs must be escaped during generation
    of local filenames. Characters that are restricted by this option are escaped, i.e.
    replaced with ‘%HH’, where ‘HH’ is the hexadecimal number that corresponds to the
    restricted character. This option may also be used to force all alphabetical cases to
    be either lower- or uppercase.
    By default, Wget escapes the characters that are not valid or safe as part of file
    names on your operating system, as well as control characters that are typically
    unprintable. This option is useful for changing these defaults, perhaps because you
    are downloading to a non-native partition, or because you want to disable escaping
    of the control characters, or you want to further restrict characters to only those in
    the ascii range of values.
    The modes are a comma-separated set of text values. The acceptable values are
    ‘unix’, ‘windows’, ‘nocontrol’, ‘ascii’, ‘lowercase’, and ‘uppercase’. The values
    ‘unix’ and ‘windows’ are mutually exclusive (one will override the other), as are
    ‘lowercase’ and ‘uppercase’. Those last are special cases, as they do not change
    the set of characters that would be escaped, but rather force local file paths to be
    converted either to lower- or uppercase.
    When “unix” is specified, Wget escapes the character ‘/’ and the control characters
    in the ranges 0–31 and 128–159. This is the default on Unix-like operating systems.
    When “windows” is given, Wget escapes the characters ‘\’, ‘|’, ‘/’, ‘:’, ‘?’, ‘"’,
    ‘*’, ‘<’, ‘>’, and the control characters in the ranges 0–31 and 128–159. In addi-
    tion to this, Wget in Windows mode uses ‘+’ instead of ‘:’ to separate host and
    Chapter 2: Invoking 12
    port in local file names, and uses ‘@’ instead of ‘?’ to separate the query por-
    tion of the file name from the rest. Therefore, a URL that would be saved as
    ‘www.xemacs.org:4300/search.pl?input=blah’ in Unix mode would be saved as
    ‘www.xemacs.org+4300/search.pl@input=blah’ in Windows mode. This mode is
    the default on Windows.
    If you specify ‘nocontrol’, then the escaping of the control characters is also
    switched off. This option may make sense when you are downloading URLs whose
    names contain UTF-8 characters, on a system which can save and display filenames
    in UTF-8 (some possible byte values used in UTF-8 byte sequences fall in the range
    of values designated by Wget as “controls”).
    The ‘ascii’ mode is used to specify that any bytes whose values are outside the
    range of ascii characters (that is, greater than 127) shall be escaped. This can be
    useful when saving filenames whose encoding does not match the one used locally.
    ‘-4’
    ‘--inet4-only’
    ‘-6’
    ‘--inet6-only’
    Force connecting to IPv4 or IPv6 addresses. With ‘--inet4-only’ or ‘-4’, Wget
    will only connect to IPv4 hosts, ignoring AAAA records in DNS, and refusing to
    connect to IPv6 addresses specified in URLs. Conversely, with ‘--inet6-only’ or
    ‘-6’, Wget will only connect to IPv6 hosts and ignore A records and IPv4 addresses.
    Neither options should be needed normally. By default, an IPv6-aware Wget will
    use the address family specified by the host’s DNS record. If the DNS responds with
    both IPv4 and IPv6 addresses, Wget will try them in sequence until it finds one it
    can connect to. (Also see --prefer-family option described below.)
    These options can be used to deliberately force the use of IPv4 or IPv6 address
    families on dual family systems, usually to aid debugging or to deal with broken
    network configuration. Only one of ‘--inet6-only’ and ‘--inet4-only’ may be
    specified at the same time. Neither option is available in Wget compiled without
    IPv6 support.
    ‘--prefer-family=none/IPv4/IPv6’
    When given a choice of several addresses, connect to the addresses with specified
    address family first. The address order returned by DNS is used without change by
    default.
    This avoids spurious errors and connect attempts when accessing hosts that resolve
    to both IPv6 and IPv4 addresses from IPv4 networks. For example, ‘www.kame.net’
    resolves to ‘2001:200:0:8002:203:47ff:fea5:3085’ and to ‘203.178.141.194’.
    When the preferred family is IPv4, the IPv4 address is used first; when the preferred
    family is IPv6, the IPv6 address is used first; if the specified value is none, the
    address order returned by DNS is used without change.
    Unlike ‘-4’ and ‘-6’, this option doesn’t inhibit access to any address family, it only
    changes the order in which the addresses are accessed. Also note that the reordering
    performed by this option is stable—it doesn’t affect order of addresses of the same
    family. That is, the relative order of all IPv4 addresses and of all IPv6 addresses
    remains intact in all cases.
    ‘--retry-connrefused’
    Consider “connection refused” a transient error and try again. Normally Wget gives
    up on a URL when it is unable to connect to the site because failure to connect
    is taken as a sign that the server is not running at all and that retries would not
    Chapter 2: Invoking 13
    help. This option is for mirroring unreliable sites whose servers tend to disappear
    for short periods of time.
    ‘--user=user’
    ‘--password=password’
    Specify the username user and password password for both ftp and http
    file retrieval. These parameters can be overridden using the ‘--ftp-user’ and
    ‘--ftp-password’ options for ftp connections and the ‘--http-user’ and
    ‘--http-password’ options for http connections.
    ‘--ask-password’
    Prompt for a password for each connection established. Cannot be specified when
    ‘--password’ is being used, because they are mutually exclusive.
    ‘--no-iri’
    Turn off internationalized URI (IRI) support. Use ‘--iri’ to turn it on. IRI support
    is activated by default.
    You can set the default state of IRI support using the iri command in ‘.wgetrc’.
    That setting may be overridden from the command line.
    ‘--local-encoding=encoding’
    Force Wget to use encoding as the default system encoding. That affects how Wget
    converts URLs specified as arguments from locale to utf-8 for IRI support.
    Wget use the function nl_langinfo() and then the CHARSET environment variable
    to get the locale. If it fails, ascii is used.
    You can set the default local encoding using the local_encoding command in
    ‘.wgetrc’. That setting may be overridden from the command line.
    ‘--remote-encoding=encoding’
    Force Wget to use encoding as the default remote server encoding. That affects
    how Wget converts URIs found in files from remote encoding to utf-8 during a
    recursive fetch. This options is only useful for IRI support, for the interpretation of
    non-ascii characters.
    For HTTP, remote encoding can be found in HTTP Content-Type header and in
    HTML Content-Type http-equiv meta tag.
    You can set the default encoding using the remoteencoding command in ‘.wgetrc’.
    That setting may be overridden from the command line.
    ‘--unlink’
    Force Wget to unlink file instead of clobbering existing file. This option is useful
    for downloading to the directory with hardlinks.
    2.6 Directory Options
    ‘-nd’
    ‘--no-directories’
    Do not create a hierarchy of directories when retrieving recursively. With this option
    turned on, all files will get saved to the current directory, without clobbering (if a
    name shows up more than once, the filenames will get extensions ‘.n’).
    ‘-x’
    ‘--force-directories’
    The opposite of ‘-nd’—create a hierarchy of directories, even if one would not have
    been created otherwise. E.g. ‘wget -x http://fly.srk.fer.hr/robots.txt’ will
    save the downloaded file to ‘fly.srk.fer.hr/robots.txt’.
    Chapter 2: Invoking 14
    ‘-nH’
    ‘--no-host-directories’
    Disable generation of host-prefixed directories. By default, invoking Wget with
    ‘-r http://fly.srk.fer.hr/’ will create a structure of directories beginning with
    ‘fly.srk.fer.hr/’. This option disables such behavior.
    ‘--protocol-directories’
    Use the protocol name as a directory component of local file names. For example,
    with this option, ‘wget -r http://host’ will save to ‘http/host/...’ rather than
    just to ‘host/...’.
    ‘--cut-dirs=number’
    Ignore number directory components. This is useful for getting a fine-grained control
    over the directory where recursive retrieval will be saved.
    Take, for example, the directory at ‘ftp://ftp.xemacs.org/pub/xemacs/’. If you
    retrieve it with ‘-r’, it will be saved locally under ‘ftp.xemacs.org/pub/xemacs/’.
    While the ‘-nH’ option can remove the ‘ftp.xemacs.org/’ part, you are still stuck
    with ‘pub/xemacs’. This is where ‘--cut-dirs’ comes in handy; it makes Wget
    not “see” number remote directory components. Here are several examples of how
    ‘--cut-dirs’ option works.
    No options -> ftp.xemacs.org/pub/xemacs/
    -nH -> pub/xemacs/
    -nH --cut-dirs=1 -> xemacs/
    -nH --cut-dirs=2 -> .
    --cut-dirs=1 -> ftp.xemacs.org/xemacs/
    ...
    If you just want to get rid of the directory structure, this option is similar to a
    combination of ‘-nd’ and ‘-P’. However, unlike ‘-nd’, ‘--cut-dirs’ does not lose
    with subdirectories—for instance, with ‘-nH --cut-dirs=1’, a ‘beta/’ subdirectory
    will be placed to ‘xemacs/beta’, as one would expect.
    ‘-P prefix’
    ‘--directory-prefix=prefix’
    Set directory prefix to prefix. The directory prefix is the directory where all other
    files and subdirectories will be saved to, i.e. the top of the retrieval tree. The default
    is ‘.’ (the current directory).
    2.7 HTTP Options
    ‘--default-page=name’
    Use name as the default file name when it isn’t known (i.e., for URLs that end in a
    slash), instead of ‘index.html’.
    ‘-E’
    ‘--adjust-extension’
    If a file of type ‘application/xhtml+xml’ or ‘text/html’ is downloaded and the
    URL does not end with the regexp ‘.[Hh][Tt][Mm][Ll]?’, this option will cause
    the suffix ‘.html’ to be appended to the local filename. This is useful, for in-
    stance, when you’re mirroring a remote site that uses ‘.asp’ pages, but you want
    the mirrored pages to be viewable on your stock Apache server. Another good
    use for this is when you’re downloading CGI-generated materials. A URL like
    http://site.com/article.cgi?25’ will be saved as ‘article.cgi?25.html’.
    Chapter 2: Invoking 15
    Note that filenames changed in this way will be re-downloaded every time you re-
    mirror a site, because Wget can’t tell that the local ‘X.html’ file corresponds to
    remote URL ‘X’ (since it doesn’t yet know that the URL produces output of type
    ‘text/html’ or ‘application/xhtml+xml’.
    As of version 1.12, Wget will also ensure that any downloaded files of type ‘text/css’
    end in the suffix ‘.css’, and the option was renamed from ‘--html-extension’, to
    better reflect its new behavior. The old option name is still acceptable, but should
    now be considered deprecated.
    At some point in the future, this option may well be expanded to include suffixes
    for other types of content, including content types that are not parsed by Wget.
    ‘--http-user=user’
    ‘--http-password=password’
    Specify the username user and password password on an http server. According to
    the type of the challenge, Wget will encode them using either the basic (insecure),
    the digest, or the Windows NTLM authentication scheme.
    Another way to specify username and password is in the url itself (see hundefinedi
    [URL Format], page hundefinedi). Either method reveals your password to anyone
    who bothers to run ps. To prevent the passwords from being seen, store them in
    ‘.wgetrc’ or ‘.netrc’, and make sure to protect those files from other users with
    chmod. If the passwords are really important, do not leave them lying in those files
    either—edit the files and delete them after Wget has started the download.
    See hundefinedi [Security Considerations], page hundefinedi, for more information
    about security issues with Wget.
    ‘--no-http-keep-alive’
    Turn off the “keep-alive” feature for HTTP downloads. Normally, Wget asks the
    server to keep the connection open so that, when you download more than one
    document from the same server, they get transferred over the same TCP connection.
    This saves time and at the same time reduces the load on the server.
    This option is useful when, for some reason, persistent (keep-alive) connections don’t
    work for you, for example due to a server bug or due to the inability of server-side
    scripts to cope with the connections.
    ‘--no-cache’
    Disable server-side cache. In this case, Wget will send the remote server an ap-
    propriate directive (‘Pragma: no-cache’) to get the file from the remote service,
    rather than returning the cached version. This is especially useful for retrieving and
    flushing out-of-date documents on proxy servers.
    Caching is allowed by default.
    ‘--no-cookies’
    Disable the use of cookies. Cookies are a mechanism for maintaining server-side
    state. The server sends the client a cookie using the Set-Cookie header, and the
    client responds with the same cookie upon further requests. Since cookies allow the
    server owners to keep track of visitors and for sites to exchange this information,
    some consider them a breach of privacy. The default is to use cookies; however,
    storing cookies is not on by default.
    ‘--load-cookies file’
    Load cookies from file before the first HTTP retrieval. file is a textual file in the
    format originally used by Netscape’s ‘cookies.txt’ file.
    You will typically use this option when mirroring sites that require that you be
    logged in to access some or all of their content. The login process typically works by
    Chapter 2: Invoking 16
    the web server issuing an http cookie upon receiving and verifying your credentials.
    The cookie is then resent by the browser when accessing that part of the site, and
    so proves your identity.
    Mirroring such a site requires Wget to send the same cookies your browser sends
    when communicating with the site. This is achieved by ‘--load-cookies’—simply
    point Wget to the location of the ‘cookies.txt’ file, and it will send the same
    cookies your browser would send in the same situation. Different browsers keep
    textual cookie files in different locations:
    Netscape 4.x.
    The cookies are in ‘~/.netscape/cookies.txt’.
    Mozilla and Netscape 6.x.
    Mozilla’s cookie file is also named ‘cookies.txt’, located somewhere
    under ‘~/.mozilla’, in the directory of your profile. The full path
    usually ends up looking somewhat like ‘~/.mozilla/default/some-
    weird-string/cookies.txt’.
    Internet Explorer.
    You can produce a cookie file Wget can use by using the File menu,
    Import and Export, Export Cookies. This has been tested with Internet
    Explorer 5; it is not guaranteed to work with earlier versions.
    Other browsers.
    If you are using a different browser to create your cookies,
    ‘--load-cookies’ will only work if you can locate or produce a cookie
    file in the Netscape format that Wget expects.
    If you cannot use ‘--load-cookies’, there might still be an alternative. If your
    browser supports a “cookie manager”, you can use it to view the cookies used when
    accessing the site you’re mirroring. Write down the name and value of the cookie,
    and manually instruct Wget to send those cookies, bypassing the “official” cookie
    support:
    wget --no-cookies --header "Cookie: name=value"
    ‘--save-cookies file’
    Save cookies to file before exiting. This will not save cookies that have ex-
    pired or that have no expiry time (so-called “session cookies”), but also see
    ‘--keep-session-cookies’.
    ‘--keep-session-cookies’
    When specified, causes ‘--save-cookies’ to also save session cookies. Session cook-
    ies are normally not saved because they are meant to be kept in memory and for-
    gotten when you exit the browser. Saving them is useful on sites that require you
    to log in or to visit the home page before you can access some pages. With this
    option, multiple Wget runs are considered a single browser session as far as the site
    is concerned.
    Since the cookie file format does not normally carry session cookies, Wget marks
    them with an expiry timestamp of 0. Wget’s ‘--load-cookies’ recognizes those
    as session cookies, but it might confuse other browsers. Also note that cookies
    so loaded will be treated as other session cookies, which means that if you want
    ‘--save-cookies’ to preserve them again, you must use ‘--keep-session-cookies’
    again.
    ‘--ignore-length’
    Unfortunately, some http servers (cgi programs, to be more precise) send out
    bogus Content-Length headers, which makes Wget go wild, as it thinks not all the
    Chapter 2: Invoking 17
    document was retrieved. You can spot this syndrome if Wget retries getting the
    same document again and again, each time claiming that the (otherwise normal)
    connection has closed on the very same byte.
    With this option, Wget will ignore the Content-Length header—as if it never ex-
    isted.
    ‘--header=header-line’
    Send header-line along with the rest of the headers in each http request. The
    supplied header is sent as-is, which means it must contain name and value separated
    by colon, and must not contain newlines.
    You may define more than one additional header by specifying ‘--header’ more
    than once.
    wget --header=’Accept-Charset: iso-8859-2’ \
    --header=’Accept-Language: hr’ \
    http://fly.srk.fer.hr/
    Specification of an empty string as the header value will clear all previous user-
    defined headers.
    As of Wget 1.10, this option can be used to override headers otherwise generated
    automatically. This example instructs Wget to connect to localhost, but to specify
    ‘foo.bar’ in the Host header:
    wget --header="Host: foo.bar" http://localhost/
    In versions of Wget prior to 1.10 such use of ‘--header’ caused sending of duplicate
    headers.
    ‘--max-redirect=number’
    Specifies the maximum number of redirections to follow for a resource. The default
    is 20, which is usually far more than necessary. However, on those occasions where
    you want to allow more (or fewer), this is the option to use.
    ‘--proxy-user=user’
    ‘--proxy-password=password’
    Specify the username user and password password for authentication on a proxy
    server. Wget will encode them using the basic authentication scheme.
    Security considerations similar to those with ‘--http-password’ pertain here as
    well.
    ‘--referer=url’
    Include ‘Referer: url’ header in HTTP request. Useful for retrieving documents with
    server-side processing that assume they are always being retrieved by interactive web
    browsers and only come out properly when Referer is set to one of the pages that
    point to them.
    ‘--save-headers’
    Save the headers sent by the http server to the file, preceding the actual contents,
    with an empty line as the separator.
    ‘-U agent-string’
    ‘--user-agent=agent-string’
    Identify as agent-string to the http server.
    The http protocol allows the clients to identify themselves using a User-Agent
    header field. This enables distinguishing the www software, usually for statis-
    tical purposes or for tracing of protocol violations. Wget normally identifies as
    ‘Wget/version’, version being the current version number of Wget.
    Chapter 2: Invoking 18
    However, some sites have been known to impose the policy of tailoring the output
    according to the User-Agent-supplied information. While this is not such a bad
    idea in theory, it has been abused by servers denying information to clients other
    than (historically) Netscape or, more frequently, Microsoft Internet Explorer. This
    option allows you to change the User-Agent line issued by Wget. Use of this option
    is discouraged, unless you really know what you are doing.
    Specifying empty user agent with ‘--user-agent=""’ instructs Wget not to send
    the User-Agent header in http requests.
    ‘--post-data=string’
    ‘--post-file=file’
    Use POST as the method for all HTTP requests and send the specified data in the
    request body. ‘--post-data’ sends string as data, whereas ‘--post-file’ sends the
    contents of file. Other than that, they work in exactly the same way. In particular,
    they both expect content of the form key1=value1&key2=value2, with percent-
    encoding for special characters; the only difference is that one expects its content as
    a command-line parameter and the other accepts its content from a file. In particu-
    lar, ‘--post-file’ is not for transmitting files as form attachments: those must ap-
    pear as key=value data (with appropriate percent-coding) just like everything else.
    Wget does not currently support multipart/form-data for transmitting POST
    data; only application/x-www-form-urlencoded. Only one of ‘--post-data’ and
    ‘--post-file’ should be specified.
    Please note that wget does not require the content to be of the form
    key1=value1&key2=value2, and neither does it test for it. Wget will simply
    transmit whatever data is provided to it. Most servers however expect the POST
    data to be in the above format when processing HTML Forms.
    When sending a POST request using the ‘--post-file’ option, Wget treats the file
    as a binary file and will send every character in the POST request without stripping
    trailing newline or formfeed characters. Any other control characters in the text
    will also be sent as-is in the POST request.
    Please be aware that Wget needs to know the size of the POST data in advance.
    Therefore the argument to --post-file must be a regular file; specifying a FIFO
    or something like ‘/dev/stdin’ won’t work. It’s not quite clear how to work around
    this limitation inherent in HTTP/1.0. Although HTTP/1.1 introduces chunked
    transfer that doesn’t require knowing the request length in advance, a client can’t
    use chunked unless it knows it’s talking to an HTTP/1.1 server. And it can’t know
    that until it receives a response, which in turn requires the request to have been
    completed – a chicken-and-egg problem.
    Note: As of version 1.15 if Wget is redirected after the POST request is completed,
    its behaviour will depend on the response code returned by the server. In case of a
    301 Moved Permanently, 302 Moved Temporarily or 307 Temporary Redirect, Wget
    will, in accordance with RFC2616, continue to send a POST request. In case a
    server wants the client to change the Request method upon redirection, it should
    send a 303 See Other response code.
    This example shows how to log in to a server using POST and then proceed to
    download the desired pages, presumably only accessible to authorized users:
    Chapter 2: Invoking 19

    Log in to the server. This can be done only once.

    wget --save-cookies cookies.txt \
    --post-data ’user=foo&password=bar’ \
    http://server.com/auth.php

    Now grab the page or pages we care about.

    wget --load-cookies cookies.txt \
    -p http://server.com/interesting/article.php
    If the server is using session cookies to track user authentication, the above will not
    work because ‘--save-cookies’ will not save them (and neither will browsers) and
    the ‘cookies.txt’ file will be empty. In that case use ‘--keep-session-cookies’
    along with ‘--save-cookies’ to force saving of session cookies.
    ‘--method=HTTP-Method’
    For the purpose of RESTful scripting, Wget allows sending of other HTTP Methods
    without the need to explicitly set them using ‘--header=Header-Line’. Wget will
    use whatever string is passed to it after ‘--method’ as the HTTP Method to the
    server.
    ‘--body-data=Data-String’
    ‘--body-file=Data-File’
    Must be set when additional data needs to be sent to the server along with the
    Method specified using ‘--method’. ‘--body-data’ sends string as data, whereas
    ‘--body-file’ sends the contents of file. Other than that, they work in exactly the
    same way.
    Currently, ‘--body-file’ is not for transmitting files as a whole. Wget does not cur-
    rently support multipart/form-data for transmitting data; only application/x-
    www-form-urlencoded. In the future, this may be changed so that wget sends the
    ‘--body-file’ as a complete file instead of sending its contents to the server. Please
    be aware that Wget needs to know the contents of BODY Data in advance, and hence
    the argument to ‘--body-file’ should be a regular file. See ‘--post-file’ for a
    more detailed explanation. Only one of ‘--body-data’ and ‘--body-file’ should
    be specified.
    If Wget is redirected after the request is completed, Wget will suspend the current
    method and send a GET request till the redirection is completed. This is true
    for all redirection response codes except 307 Temporary Redirect which is used to
    explicitly specify that the request method should not change. Another exception is
    when the method is set to POST, in which case the redirection rules specified under
    ‘--post-data’ are followed.
    ‘--content-disposition’
    If this is set to on, experimental (not fully-functional) support for Content-
    Disposition headers is enabled. This can currently result in extra round-trips
    to the server for a HEAD request, and is known to suffer from a few bugs, which is
    why it is not currently enabled by default.
    This option is useful for some file-downloading CGI programs that use Content-
    Disposition headers to describe what the name of a downloaded file should be.
    ‘--content-on-error’
    If this is set to on, wget will not skip the content when the server responds with a
    http status code that indicates error.
    Chapter 2: Invoking 20
    ‘--trust-server-names’
    If this is set to on, on a redirect the last component of the redirection URL will be
    used as the local file name. By default it is used the last component in the original
    URL.
    ‘--auth-no-challenge’
    If this option is given, Wget will send Basic HTTP authentication information
    (plaintext username and password) for all requests, just like Wget 1.10.2 and prior
    did by default.
    Use of this option is not recommended, and is intended only to support some few
    obscure servers, which never send HTTP authentication challenges, but accept un-
    solicited auth info, say, in addition to form-based authentication.
    2.8 HTTPS (SSL/TLS) Options
    To support encrypted HTTP (HTTPS) downloads, Wget must be compiled with an external
    SSL library. The current default is GnuTLS. In addition, Wget also supports HSTS (HTTP
    Strict Transport Security). If Wget is compiled without SSL support, none of these options are
    available.
    ‘--secure-protocol=protocol’
    Choose the secure protocol to be used. Legal values are ‘auto’, ‘SSLv2’, ‘SSLv3’,
    ‘TLSv1’, ‘TLSv11’, ‘TLSv1_2’ and ‘PFS’. If ‘auto’ is used, the SSL library is given
    the liberty of choosing the appropriate protocol automatically, which is achieved by
    sending a TLSv1 greeting. This is the default.
    Specifying ‘SSLv2’, ‘SSLv3’, ‘TLSv1’, ‘TLSv1_1’ or ‘TLSv1_2’ forces the use of the
    corresponding protocol. This is useful when talking to old and buggy SSL server
    implementations that make it hard for the underlying SSL library to choose the
    correct protocol version. Fortunately, such servers are quite rare.
    Specifying ‘PFS’ enforces the use of the so-called Perfect Forward Security cipher
    suites. In short, PFS adds security by creating a one-time key for each SSL con-
    nection. It has a bit more CPU impact on client and server. We use known to be
    secure ciphers (e.g. no MD4) and the TLS protocol.
    ‘--https-only’
    When in recursive mode, only HTTPS links are followed.
    ‘--no-check-certificate’
    Don’t check the server certificate against the available certificate authorities. Also
    don’t require the URL host name to match the common name presented by the
    certificate.
    As of Wget 1.10, the default is to verify the server’s certificate against the recog-
    nized certificate authorities, breaking the SSL handshake and aborting the download
    if the verification fails. Although this provides more secure downloads, it does break
    interoperability with some sites that worked with previous Wget versions, particu-
    larly those using self-signed, expired, or otherwise invalid certificates. This option
    forces an “insecure” mode of operation that turns the certificate verification errors
    into warnings and allows you to proceed.
    If you encounter “certificate verification” errors or ones saying that “common name
    doesn’t match requested host name”, you can use this option to bypass the verifi-
    cation and proceed with the download. Only use this option if you are otherwise
    convinced of the site’s authenticity, or if you really don’t care about the validity of
    its certificate. It is almost always a bad idea not to check the certificates when
    Chapter 2: Invoking 21
    transmitting confidential or important data. For self-signed/internal certificates,
    you should download the certificate and verify against that instead of forcing this
    insecure mode. If you are really sure of not desiring any certificate verification, you
    can specify –check-certificate=quiet to tell wget to not print any warning about
    invalid certificates, albeit in most cases this is the wrong thing to do.
    ‘--certificate=file’
    Use the client certificate stored in file. This is needed for servers that are configured
    to require certificates from the clients that connect to them. Normally a certificate
    is not required and this switch is optional.
    ‘--certificate-type=type’
    Specify the type of the client certificate. Legal values are ‘PEM’ (assumed by default)
    and ‘DER’, also known as ‘ASN1’.
    ‘--private-key=file’
    Read the private key from file. This allows you to provide the private key in a file
    separate from the certificate.
    ‘--private-key-type=type’
    Specify the type of the private key. Accepted values are ‘PEM’ (the default) and
    ‘DER’.
    ‘--ca-certificate=file’
    Use file as the file with the bundle of certificate authorities (“CA”) to verify the
    peers. The certificates must be in PEM format.
    Without this option Wget looks for CA certificates at the system-specified locations,
    chosen at OpenSSL installation time.
    ‘--ca-directory=directory’
    Specifies directory containing CA certificates in PEM format. Each file contains
    one CA certificate, and the file name is based on a hash value derived from the cer-
    tificate. This is achieved by processing a certificate directory with the c_rehash
    utility supplied with OpenSSL. Using ‘--ca-directory’ is more efficient than
    ‘--ca-certificate’ when many certificates are installed because it allows Wget
    to fetch certificates on demand.
    Without this option Wget looks for CA certificates at the system-specified locations,
    chosen at OpenSSL installation time.
    ‘--crl-file=file’
    Specifies a CRL file in file. This is needed for certificates that have been revocated
    by the CAs.
    ‘--random-file=file’
    [OpenSSL and LibreSSL only] Use file as the source of random data for seeding the
    pseudo-random number generator on systems without ‘/dev/urandom’.
    On such systems the SSL library needs an external source of randomness to initialize.
    Randomness may be provided by EGD (see ‘--egd-file’ below) or read from an
    external source specified by the user. If this option is not specified, Wget looks for
    random data in $RANDFILE or, if that is unset, in ‘$HOME/.rnd’.
    If you’re getting the “Could not seed OpenSSL PRNG; disabling SSL.” error, you
    should provide random data using some of the methods described above.
    ‘--egd-file=file’
    [OpenSSL only] Use file as the EGD socket. EGD stands for Entropy Gathering
    Daemon, a user-space program that collects data from various unpredictable system
    Chapter 2: Invoking 22
    sources and makes it available to other programs that might need it. Encryption
    software, such as the SSL library, needs sources of non-repeating randomness to seed
    the random number generator used to produce cryptographically strong keys.
    OpenSSL allows the user to specify his own source of entropy using the RAND

    FILE environment variable. If this variable is unset, or if the specified file does not
    produce enough randomness, OpenSSL will read random data from EGD socket
    specified using this option.
    If this option is not specified (and the equivalent startup command is not used),
    EGD is never contacted. EGD is not needed on modern Unix systems that support
    ‘/dev/urandom’.
    ‘--no-hsts’
    Wget supports HSTS (HTTP Strict Transport Security, RFC 6797) by default. Use
    ‘--no-hsts’ to make Wget act as a non-HSTS-compliant UA. As a consequence,
    Wget would ignore all the Strict-Transport-Security headers, and would not
    enforce any existing HSTS policy.
    ‘--hsts-file=file’
    By default, Wget stores its HSTS database in ‘~/.wget-hsts’. You can use
    ‘--hsts-file’ to override this. Wget will use the supplied file as the HSTS data-
    base. Such file must conform to the correct HSTS database format used by Wget.
    If Wget cannot parse the provided file, the behaviour is unspecified.
    The Wget’s HSTS database is a plain text file. Each line contains an HSTS entry
    (ie. a site that has issued a Strict-Transport-Security header and that therefore
    has specified a concrete HSTS policy to be applied). Lines starting with a dash (#)
    are ignored by Wget. Please note that in spite of this convenient human-readability
    hand-hacking the HSTS database is generally not a good idea.
    An HSTS entry line consists of several fields separated by one or more whitespace:
    SP [] SP SP SP
    The hostname and port fields indicate the hostname and port to which the given
    HSTS policy applies. The port field may be zero, and it will, in most of the cases.
    That means that the port number will not be taken into account when deciding
    whether such HSTS policy should be applied on a given request (only the host-
    name will be evaluated). When port is different to zero, both the target hostname
    and the port will be evaluated and the HSTS policy will only be applied if both
    of them match. This feature has been included for testing/development purposes
    only. The Wget testsuite (in ‘testenv/’) creates HSTS databases with explicit ports
    with the purpose of ensuring Wget’s correct behaviour. Applying HSTS policies to
    ports other than the default ones is discouraged by RFC 6797 (see Appendix B
    "Differences between HSTS Policy and Same-Origin Policy"). Thus, this function-
    ality should not be used in production environments and port will typically be zero.
    The last three fields do what they are expected to. The field include subdomains
    can either be 1 or 0 and it signals whether the subdomains of the target domain
    should be part of the given HSTS policy as well. The created and max-age fields
    hold the timestamp values of when such entry was created (first seen by Wget)
    and the HSTS-defined value ’max-age’, which states how long should that HSTS
    policy remain active, measured in seconds elapsed since the timestamp stored in
    created. Once that time has passed, that HSTS policy will no longer be valid and
    will eventually be removed from the database.
    If you supply your own HSTS database via ‘--hsts-file’, be aware that Wget may
    modify the provided file if any change occurs between the HSTS policies requested
    Chapter 2: Invoking 23
    by the remote servers and those in the file. When Wget exists, it effectively updates
    the HSTS database by rewriting the database file with the new entries.
    If the supplied file does not exist, Wget will create one. This file will contain the new
    HSTS entries. If no HSTS entries were generated (no Strict-Transport-Security
    headers were sent by any of the servers) then no file will be created, not even an
    empty one. This behaviour applies to the default database file (‘~/.wget-hsts’) as
    well: it will not be created until some server enforces an HSTS policy.
    Care is taken not to override possible changes made by other Wget processes at the
    same time over the HSTS database. Before dumping the updated HSTS entries on
    the file, Wget will re-read it and merge the changes.
    Using a custom HSTS database and/or modifying an existing one is discouraged. For
    more information about the potential security threats arised from such practice, see
    section 14 "Security Considerations" of RFC 6797, specially section 14.9 "Creative
    Manipulation of HSTS Policy Store".
    ‘--warc-file=file’
    Use file as the destination WARC file.
    ‘--warc-header=string’
    Use string into as the warcinfo record.
    ‘--warc-max-size=size’
    Set the maximum size of the WARC files to size.
    ‘--warc-cdx’
    Write CDX index files.
    ‘--warc-dedup=file’
    Do not store records listed in this CDX file.
    ‘--no-warc-compression’
    Do not compress WARC files with GZIP.
    ‘--no-warc-digests’
    Do not calculate SHA1 digests.
    ‘--no-warc-keep-log’
    Do not store the log file in a WARC record.
    ‘--warc-tempdir=dir’
    Specify the location for temporary files created by the WARC writer.
    2.9 FTP Options
    ‘--ftp-user=user’
    ‘--ftp-password=password’
    Specify the username user and password password on an ftp server. Without this,
    or the corresponding startup option, the password defaults to ‘-wget@’, normally
    used for anonymous FTP.
    Another way to specify username and password is in the url itself (see hundefinedi
    [URL Format], page hundefinedi). Either method reveals your password to anyone
    who bothers to run ps. To prevent the passwords from being seen, store them in
    ‘.wgetrc’ or ‘.netrc’, and make sure to protect those files from other users with
    chmod. If the passwords are really important, do not leave them lying in those files
    either—edit the files and delete them after Wget has started the download.
    See hundefinedi [Security Considerations], page hundefinedi, for more information
    about security issues with Wget.
    Chapter 2: Invoking 24
    ‘--no-remove-listing’
    Don’t remove the temporary ‘.listing’ files generated by ftp retrievals. Normally,
    these files contain the raw directory listings received from ftp servers. Not removing
    them can be useful for debugging purposes, or when you want to be able to easily
    check on the contents of remote server directories (e.g. to verify that a mirror you’re
    running is complete).
    Note that even though Wget writes to a known filename for this file, this is not
    a security hole in the scenario of a user making ‘.listing’ a symbolic link to
    ‘/etc/passwd’ or something and asking root to run Wget in his or her directory.
    Depending on the options used, either Wget will refuse to write to ‘.listing’, mak-
    ing the globbing/recursion/time-stamping operation fail, or the symbolic link will
    be deleted and replaced with the actual ‘.listing’ file, or the listing will be written
    to a ‘.listing.number’ file.
    Even though this situation isn’t a problem, though, root should never run Wget
    in a non-trusted user’s directory. A user could do something as simple as linking
    ‘index.html’ to ‘/etc/passwd’ and asking root to run Wget with ‘-N’ or ‘-r’ so
    the file will be overwritten.
    ‘--no-glob’
    Turn off ftp globbing. Globbing refers to the use of shell-like special characters
    (wildcards), like ‘’, ‘?’, ‘[’ and ‘]’ to retrieve more than one file from the same
    directory at once, like:
    wget ftp://gnjilux.srk.fer.hr/
    .msg
    By default, globbing will be turned on if the url contains a globbing character.
    This option may be used to turn globbing on or off permanently.
    You may have to quote the url to protect it from being expanded by your shell.
    Globbing makes Wget look for a directory listing, which is system-specific. This is
    why it currently works only with Unix ftp servers (and the ones emulating Unix ls
    output).
    ‘--no-passive-ftp’
    Disable the use of the passive FTP transfer mode. Passive FTP mandates that the
    client connect to the server to establish the data connection rather than the other
    way around.
    If the machine is connected to the Internet directly, both passive and active FTP
    should work equally well. Behind most firewall and NAT configurations passive
    FTP has a better chance of working. However, in some rare firewall configurations,
    active FTP actually works when passive FTP doesn’t. If you suspect this to be the
    case, use this option, or set passive_ftp=off in your init file.
    ‘--preserve-permissions’
    Preserve remote file permissions instead of permissions set by umask.
    ‘--retr-symlinks’
    By default, when retrieving ftp directories recursively and a symbolic link is encoun-
    tered, the symbolic link is traversed and the pointed-to files are retrieved. Currently,
    Wget does not traverse symbolic links to directories to download them recursively,
    though this feature may be added in the future.
    When ‘--retr-symlinks=no’ is specified, the linked-to file is not downloaded. In-
    stead, a matching symbolic link is created on the local filesystem. The pointed-to
    file will not be retrieved unless this recursive retrieval would have encountered it
    separately and downloaded it anyway. This option poses a security risk where a
    Chapter 2: Invoking 25
    malicious FTP Server may cause Wget to write to files outside of the intended
    directories through a specially crafted .listing file.
    Note that when retrieving a file (not a directory) because it was specified on the
    command-line, rather than because it was recursed to, this option has no effect.
    Symbolic links are always traversed in this case.
    2.10 FTPS Options
    ‘--ftps-implicit’
    This option tells Wget to use FTPS implicitly. Implicit FTPS consists of initializing
    SSL/TLS from the very beginning of the control connection. This option does not
    send an AUTH TLS command: it assumes the server speaks FTPS and directly starts
    an SSL/TLS connection. If the attempt is successful, the session continues just
    like regular FTPS (PBSZ and PROT are sent, etc.). Implicit FTPS is no longer a
    requirement for FTPS implementations, and thus many servers may not support it.
    If ‘--ftps-implicit’ is passed and no explicit port number specified, the default
    port for implicit FTPS, 990, will be used, instead of the default port for the "normal"
    (explicit) FTPS which is the same as that of FTP, 21.
    ‘--no-ftps-resume-ssl’
    Do not resume the SSL/TLS session in the data channel. When starting a data
    connection, Wget tries to resume the SSL/TLS session previously started in the
    control connection. SSL/TLS session resumption avoids performing an entirely new
    handshake by reusing the SSL/TLS parameters of a previous session. Typically,
    the FTPS servers want it that way, so Wget does this by default. Under rare
    circumstances however, one might want to start an entirely new SSL/TLS session
    in every data connection. This is what ‘--no-ftps-resume-ssl’ is for.
    ‘--ftps-clear-data-connection’
    All the data connections will be in plain text. Only the control connection will be
    under SSL/TLS. Wget will send a PROT C command to achieve this, which must be
    approved by the server.
    ‘--ftps-fallback-to-ftp’
    Fall back to FTP if FTPS is not supported by the target server. For security reasons,
    this option is not asserted by default. The default behaviour is to exit with an error.
    If a server does not successfully reply to the initial AUTH TLS command, or in the
    case of implicit FTPS, if the initial SSL/TLS connection attempt is rejected, it is
    considered that such server does not support FTPS.
    2.11 Recursive Retrieval Options
    ‘-r’
    ‘--recursive’
    Turn on recursive retrieving. See hundefinedi [Recursive Download], page hunde-
    finedi, for more details. The default maximum depth is 5.
    ‘-l depth’
    ‘--level=depth’
    Specify recursion maximum depth level depth (see hundefinedi [Recursive Down-
    load], page hundefinedi).
    ‘--delete-after’
    This option tells Wget to delete every single file it downloads, after having done so.
    It is useful for pre-fetching popular pages through a proxy, e.g.:
    Chapter 2: Invoking 26
    wget -r -nd --delete-after http://whatever.com/~popular/page/
    The ‘-r’ option is to retrieve recursively, and ‘-nd’ to not create directories.
    Note that ‘--delete-after’ deletes files on the local machine. It does not is-
    sue the ‘DELE’ command to remote FTP sites, for instance. Also note that when
    ‘--delete-after’ is specified, ‘--convert-links’ is ignored, so ‘.orig’ files are
    simply not created in the first place.
    ‘-k’
    ‘--convert-links’
    After the download is complete, convert the links in the document to make them
    suitable for local viewing. This affects not only the visible hyperlinks, but any part
    of the document that links to external content, such as embedded images, links to
    style sheets, hyperlinks to non-html content, etc.
    Each link will be changed in one of the two ways:
    • The links to files that have been downloaded by Wget will be changed to refer
    to the file they point to as a relative link.
    Example: if the downloaded file ‘/foo/doc.html’ links to ‘/bar/img.gif’,
    also downloaded, then the link in ‘doc.html’ will be modified to point to
    ‘../bar/img.gif’. This kind of transformation works reliably for arbitrary
    combinations of directories.
    • The links to files that have not been downloaded by Wget will be changed to
    include host name and absolute path of the location they point to.
    Example: if the downloaded file ‘/foo/doc.html’ links to ‘/bar/img.gif’ (or
    to ‘../bar/img.gif’), then the link in ‘doc.html’ will be modified to point to
    http://hostname/bar/img.gif’.
    Because of this, local browsing works reliably: if a linked file was downloaded, the
    link will refer to its local name; if it was not downloaded, the link will refer to its full
    Internet address rather than presenting a broken link. The fact that the former links
    are converted to relative links ensures that you can move the downloaded hierarchy
    to another directory.
    Note that only at the end of the download can Wget know which links have been
    downloaded. Because of that, the work done by ‘-k’ will be performed at the end
    of all the downloads.
    ‘--convert-file-only’
    This option converts only the filename part of the URLs, leaving the rest of the
    URLs untouched. This filename part is sometimes referred to as the "basename",
    although we avoid that term here in order not to cause confusion.
    It works particularly well in conjunction with ‘--adjust-extension’, although this
    coupling is not enforced. It proves useful to populate Internet caches with files
    downloaded from different hosts.
    Example: if some link points to ‘//foo.com/bar.cgi?xyz’ with
    ‘--adjust-extension’ asserted and its local destination is intended to
    be ‘./foo.com/bar.cgi?xyz.css’, then the link would be converted to
    ‘//foo.com/bar.cgi?xyz.css’. Note that only the filename part has been
    modified. The rest of the URL has been left untouched, including the net path
    (//) which would otherwise be processed by Wget and converted to the effective
    scheme (ie. http://).
    Chapter 2: Invoking 27
    ‘-K’
    ‘--backup-converted’
    When converting a file, back up the original version with a ‘.orig’ suffix. Affects
    the behavior of ‘-N’ (see hundefinedi [HTTP Time-Stamping Internals], page hun-
    definedi).
    ‘-m’
    ‘--mirror’
    Turn on options suitable for mirroring. This option turns on recursion and time-
    stamping, sets infinite recursion depth and keeps ftp directory listings. It is cur-
    rently equivalent to ‘-r -N -l inf --no-remove-listing’.
    ‘-p’
    ‘--page-requisites’
    This option causes Wget to download all the files that are necessary to properly
    display a given html page. This includes such things as inlined images, sounds,
    and referenced stylesheets.
    Ordinarily, when downloading a single html page, any requisite documents that
    may be needed to display it properly are not downloaded. Using ‘-r’ together with
    ‘-l’ can help, but since Wget does not ordinarily distinguish between external and
    inlined documents, one is generally left with “leaf documents” that are missing their
    requisites.
    For instance, say document ‘1.html’ contains an tag referencing ‘1.gif’ and
    an tag pointing to external document ‘2.html’. Say that ‘2.html’ is similar
    but that its image is ‘2.gif’ and it links to ‘3.html’. Say this continues up to some
    arbitrarily high number.
    If one executes the command:
    wget -r -l 2
    http://site/1.html
    then ‘1.html’, ‘1.gif’, ‘2.html’, ‘2.gif’, and ‘3.html’ will be downloaded. As you
    can see, ‘3.html’ is without its requisite ‘3.gif’ because Wget is simply counting
    the number of hops (up to 2) away from ‘1.html’ in order to determine where to
    stop the recursion. However, with this command:
    wget -r -l 2 -p http://site/1.html
    all the above files and ‘3.html’’s requisite ‘3.gif’ will be downloaded. Similarly,
    wget -r -l 1 -p http://site/1.html
    will cause ‘1.html’, ‘1.gif’, ‘2.html’, and ‘2.gif’ to be downloaded. One might
    think that:
    wget -r -l 0 -p http://site/1.html
    would download just ‘1.html’ and ‘1.gif’, but unfortunately this is not the case,
    because ‘-l 0’ is equivalent to ‘-l inf’—that is, infinite recursion. To download a
    single html page (or a handful of them, all specified on the command-line or in a
    ‘-i’ url input file) and its (or their) requisites, simply leave off ‘-r’ and ‘-l’:
    wget -p http://site/1.html
    Note that Wget will behave as if ‘-r’ had been specified, but only that single page
    and its requisites will be downloaded. Links from that page to external documents
    will not be followed. Actually, to download a single page and all its requisites (even
    if they exist on separate websites), and make sure the lot displays properly locally,
    this author likes to use a few options in addition to ‘-p’:
    wget -E -H -k -K -p http://site/document
    Chapter 2: Invoking 28
    To finish off this topic, it’s worth knowing that Wget’s idea of an external document
    link is any URL specified in an tag, an tag, or a tag other than
    .
    ‘--strict-comments’
    Turn on strict parsing of html comments. The default is to terminate comments
    at the first occurrence of ‘-->’.
    According to specifications, html comments are expressed as sgml declarations.
    Declaration is special markup that begins with ‘<!’ and ends with ‘>’, such as
    ‘<!DOCTYPE ...>’, that may contain comments between a pair of ‘--’ delimiters.
    html comments are “empty declarations”, sgml declarations without any non-
    comment text. Therefore, ‘’ is a valid comment, and so is ‘’, but ‘’ is not.
    On the other hand, most html writers don’t perceive comments as anything other
    than text delimited with ‘’, which is not quite the same. For example,
    something like ‘’ works as a valid comment as long as the number
    of dashes is a multiple of four (!). If not, the comment technically lasts until the
    next ‘--’, which may be at the other end of the document. Because of this, many
    popular browsers completely ignore the specificationand implement what users have
    come to expect: comments delimited with ‘’.
    Until version 1.9, Wget interpreted comments strictly, which resulted in missing
    links in many web pages that displayed fine in browsers, but had the misfortune of
    containing non-compliant comments. Beginning with version 1.9, Wget has joined
    the ranks of clients that implements “naive” comments, terminating each comment
    at the first occurrence of ‘-->’.
    If, for whatever reason, you want strict comment parsing, use this option to turn it
    on.
    2.12 Recursive Accept/Reject Options
    ‘-A acclist --accept acclist’
    ‘-R rejlist --reject rejlist’
    Specify comma-separated lists of file name suffixes or patterns to accept or reject
    (see hundefinedi [Types of Files], page hundefinedi). Note that if any of the wildcard
    characters, ‘’, ‘?’, ‘[’ or ‘]’, appear in an element of acclist or rejlist, it will be
    treated as a pattern, rather than a suffix. In this case, you have to enclose the
    pattern into quotes to prevent your shell from expanding it, like in ‘-A "
    .mp3"’ or
    ‘-A ’.mp3’’.
    ‘--accept-regex urlregex’
    ‘--reject-regex urlregex’
    Specify a regular expression to accept or reject the complete URL.
    ‘--regex-type regextype’
    Specify the regular expression type. Possible types are ‘posix’ or ‘pcre’. Note that
    to be able to use ‘pcre’ type, wget has to be compiled with libpcre support.
    ‘-D domain-list’
    ‘--domains=domain-list’
    Set domains to be followed. domain-list is a comma-separated list of domains. Note
    that it does not turn on ‘-H’.
    ‘--exclude-domains domain-list’
    Specify the domains that are not to be followed (see hundefinedi [Spanning Hosts],
    page hundefinedi).
    Chapter 2: Invoking 29
    ‘--follow-ftp’
    Follow ftp links from html documents. Without this option, Wget will ignore all
    the ftp links.
    ‘--follow-tags=list’
    Wget has an internal table of html tag / attribute pairs that it considers when
    looking for linked documents during a recursive retrieval. If a user wants only a
    subset of those tags to be considered, however, he or she should be specify such tags
    in a comma-separated list with this option.
    ‘--ignore-tags=list’
    This is the opposite of the ‘--follow-tags’ option. To skip certain html tags when
    recursively looking for documents to download, specify them in a comma-separated
    list.
    In the past, this option was the best bet for downloading a single page and its
    requisites, using a command-line like:
    wget --ignore-tags=a,area -H -k -K -r
    http://site/document
    However, the author of this option came across a page with tags like and came to the realization that specifying tags to ignore
    was not enough. One can’t just tell Wget to ignore , because then stylesheets
    will not be downloaded. Now the best bet for downloading a single page and its
    requisites is the dedicated ‘--page-requisites’ option.
    ‘--ignore-case’
    Ignore case when matching files and directories. This influences the behavior of -R,
    -A, -I, and -X options, as well as globbing implemented when downloading from
    FTP sites. For example, with this option, ‘-A "
    .txt"’ will match ‘file1.txt’,
    but also ‘file2.TXT’, ‘file3.TxT’, and so on. The quotes in the example are to
    prevent the shell from expanding the pattern.
    ‘-H’
    ‘--span-hosts’
    Enable spanning across hosts when doing recursive retrieving (see hundefinedi [Span-
    ning Hosts], page hundefinedi).
    ‘-L’
    ‘--relative’
    Follow relative links only. Useful for retrieving a specific home page without any
    distractions, not even those from the same hosts (see hundefinedi [Relative Links],
    page hundefinedi).
    ‘-I list’
    ‘--include-directories=list’
    Specify a comma-separated list of directories you wish to follow when downloading
    (see hundefinedi [Directory-Based Limits], page hundefinedi). Elements of list may
    contain wildcards.
    ‘-X list’
    ‘--exclude-directories=list’
    Specify a comma-separated list of directories you wish to exclude from download
    (see hundefinedi [Directory-Based Limits], page hundefinedi). Elements of list may
    contain wildcards.
    ‘-np’
    Chapter 2: Invoking 30
    ‘--no-parent’
    Do not ever ascend to the parent directory when retrieving recursively. This is a
    useful option, since it guarantees that only the files below a certain hierarchy will be
    downloaded. See hundefinedi [Directory-Based Limits], page hundefinedi, for more
    details.
    2.13 Exit Status
    Wget may return one of several error codes if it encounters problems.
    0 No problems occurred.
    1 Generic error code.
    2 Parse error—for instance, when parsing command-line options, the ‘.wgetrc’ or
    ‘.netrc’...
    3 File I/O error.
    4 Network failure.
    5 SSL verification failure.
    6 Username/password authentication failure.
    7 Protocol errors.
    8 Server issued an error response.
    With the exceptions of 0 and 1, the lower-numbered exit codes take precedence over higher-
    numbered ones, when multiple types of errors are encountered.
    In versions of Wget prior to 1.12, Wget’s exit status tended to be unhelpful and incon-
    sistent. Recursive downloads would virtually always return 0 (success), regardless of any is-
    sues encountered, and non-recursive fetches only returned the status corresponding to the most
    recently-attempted download.
    Chapter 3: Recursive Download 31
    3 Recursive Download
    GNU Wget is capable of traversing parts of the Web (or a single http or ftp server), following
    links and directory structure. We refer to this as to recursive retrieval, or recursion.
    With http urls, Wget retrieves and parses the html or css from the given url, retrieving
    the files the document refers to, through markup like href or src, or css uri values specified
    using the ‘url()’ functional notation. If the freshly downloaded file is also of type text/html,
    application/xhtml+xml, or text/css, it will be parsed and followed further.
    Recursive retrieval of http and html/css content is breadth-first. This means that Wget
    first downloads the requested document, then the documents linked from that document, then
    the documents linked by them, and so on. In other words, Wget first downloads the documents
    at depth 1, then those at depth 2, and so on until the specified maximum depth.
    The maximum depth to which the retrieval may descend is specified with the ‘-l’ option.
    The default maximum depth is five layers.
    When retrieving an ftp url recursively, Wget will retrieve all the data from the given
    directory tree (including the subdirectories up to the specified depth) on the remote server,
    creating its mirror image locally. ftp retrieval is also limited by the depth parameter. Unlike
    http recursion, ftp recursion is performed depth-first.
    By default, Wget will create a local directory tree, corresponding to the one found on the
    remote server.
    Recursive retrieving can find a number of applications, the most important of which is mir-
    roring. It is also useful for www presentations, and any other opportunities where slow network
    connections should be bypassed by storing the files locally.
    You should be warned that recursive downloads can overload the remote servers. Because of
    that, many administrators frown upon them and may ban access from your site if they detect very
    fast downloads of big amounts of content. When downloading from Internet servers, consider
    using the ‘-w’ option to introduce a delay between accesses to the server. The download will
    take a while longer, but the server administrator will not be alarmed by your rudeness.
    Of course, recursive download may cause problems on your machine. If left to run unchecked,
    it can easily fill up the disk. If downloading from local network, it can also take bandwidth on
    the system, as well as consume memory and CPU.
    Try to specify the criteria that match the kind of download you are trying to achieve. If you
    want to download only one page, use ‘--page-requisites’ without any additional recursion. If
    you want to download things under one directory, use ‘-np’ to avoid downloading things from
    other directories. If you want to download all the files from one directory, use ‘-l 1’ to make
    sure the recursion depth never exceeds one. See hundefinedi [Following Links], page hundefinedi,
    for more information about this.
    Recursive retrieval should be used with care. Don’t say you were not warned.
    Chapter 4: Following Links 32
    4 Following Links
    When retrieving recursively, one does not wish to retrieve loads of unnecessary data. Most of
    the time the users bear in mind exactly what they want to download, and want Wget to follow
    only specific links.
    For example, if you wish to download the music archive from ‘fly.srk.fer.hr’, you will not
    want to download all the home pages that happen to be referenced by an obscure part of the
    archive.
    Wget possesses several mechanisms that allows you to fine-tune which links it will follow.
    4.1 Spanning Hosts
    Wget’s recursive retrieval normally refuses to visit hosts different than the one you specified
    on the command line. This is a reasonable default; without it, every retrieval would have the
    potential to turn your Wget into a small version of google.
    However, visiting different hosts, or host spanning, is sometimes a useful option. Maybe the
    images are served from a different server. Maybe you’re mirroring a site that consists of pages
    interlinked between three servers. Maybe the server has two equivalent names, and the html
    pages refer to both interchangeably.
    Span to any host—‘-H’
    The ‘-H’ option turns on host spanning, thus allowing Wget’s recursive run to visit
    any host referenced by a link. Unless sufficient recursion-limiting criteria are applied
    depth, these foreign hosts will typically link to yet more hosts, and so on until Wget
    ends up sucking up much more data than you have intended.
    Limit spanning to certain domains—‘-D’
    The ‘-D’ option allows you to specify the domains that will be followed, thus limiting
    the recursion only to the hosts that belong to these domains. Obviously, this makes
    sense only in conjunction with ‘-H’. A typical example would be downloading the
    contents of ‘www.server.com’, but allowing downloads from ‘images.server.com’,
    etc.:
    wget -rH -Dserver.com http://www.server.com/
    You can specify more than one address by separating them with a comma, e.g.
    ‘-Ddomain1.com,domain2.com’.
    Keep download off certain domains—‘--exclude-domains’
    If there are domains you want to exclude specifically, you can do it with
    ‘--exclude-domains’, which accepts the same type of arguments of ‘-D’, but will
    exclude all the listed domains. For example, if you want to download all the hosts
    from ‘foo.edu’ domain, with the exception of ‘sunsite.foo.edu’, you can do it
    like this:
    wget -rH -Dfoo.edu --exclude-domains sunsite.foo.edu \
    http://www.foo.edu/
    4.2 Types of Files
    When downloading material from the web, you will often want to restrict the retrieval to only
    certain file types. For example, if you are interested in downloading gifs, you will not be
    overjoyed to get loads of PostScript documents, and vice versa.
    Wget offers two options to deal with this problem. Each option description lists a short
    name, a long name, and the equivalent command in ‘.wgetrc’.
    Chapter 4: Following Links 33
    ‘-A acclist’
    ‘--accept acclist’
    ‘accept = acclist’
    ‘--accept-regex urlregex’
    ‘accept-regex = urlregex’
    The argument to ‘--accept’ option is a list of file suffixes or patterns that Wget
    will download during recursive retrieval. A suffix is the ending part of a file, and
    consists of “normal” letters, e.g. ‘gif’ or ‘.jpg’. A matching pattern contains
    shell-like wildcards, e.g. ‘books’ or ‘zelazny196[0-9]’.
    So, specifying ‘wget -A gif,jpg’ will make Wget download only the files end-
    ing with ‘gif’ or ‘jpg’, i.e. gifs and jpegs. On the other hand, ‘wget -A
    "zelazny
    196[0-9]"’ will download only files beginning with ‘zelazny’ and con-
    taining numbers from 1960 to 1969 anywhere within. Look up the manual of your
    shell for a description of how pattern matching works.
    Of course, any number of suffixes and patterns can be combined into a comma-
    separated list, and given as an argument to ‘-A’.
    The argument to ‘--accept-regex’ option is a regular expression which is matched
    against the complete URL.
    ‘-R rejlist’
    ‘--reject rejlist’
    ‘reject = rejlist’
    ‘--reject-regex urlregex’
    ‘reject-regex = urlregex’
    The ‘--reject’ option works the same way as ‘--accept’, only its logic is the re-
    verse; Wget will download all files except the ones matching the suffixes (or patterns)
    in the list.
    So, if you want to download a whole page except for the cumbersome mpegs and
    .au files, you can use ‘wget -R mpg,mpeg,au’. Analogously, to download all files
    except the ones beginning with ‘bjork’, use ‘wget -R "bjork
    "’. The quotes are to
    prevent expansion by the shell.
    The argument to ‘--accept-regex’ option is a regular expression which is matched against
    the complete URL.
    The ‘-A’ and ‘-R’ options may be combined to achieve even better fine-tuning of which files to
    retrieve. E.g. ‘wget -A "zelazny" -R .ps’ will download all the files having ‘zelazny’ as a
    part of their name, but not the PostScript files.
    Note that these two options do not affect the downloading of html files (as determined by
    a ‘.htm’ or ‘.html’ filename prefix). This behavior may not be desirable for all users, and may
    be changed for future versions of Wget.
    Note, too, that query strings (strings at the end of a URL beginning with a question mark
    (‘?’) are not included as part of the filename for accept/reject rules, even though these will
    actually contribute to the name chosen for the local file. It is expected that a future version of
    Wget will provide an option to allow matching against query strings.
    Finally, it’s worth noting that the accept/reject lists are matched twice against downloaded
    files: once against the URL’s filename portion, to determine if the file should be downloaded
    in the first place; then, after it has been accepted and successfully downloaded, the local file’s
    name is also checked against the accept/reject lists to see if it should be removed. The rationale
    was that, since ‘.htm’ and ‘.html’ files are always downloaded regardless of accept/reject rules,
    they should be removed after being downloaded and scanned for links, if they did match the
    accept/reject lists. However, this can lead to unexpected results, since the local filenames can
    Chapter 4: Following Links 34
    differ from the original URL filenames in the following ways, all of which can change whether
    an accept/reject rule matches:
    • If the local file already exists and ‘--no-directories’ was specified, a numeric suffix will
    be appended to the original name.
    • If ‘--adjust-extension’ was specified, the local filename might have ‘.html’ appended
    to it. If Wget is invoked with ‘-E -A.php’, a filename such as ‘index.php’ will match be
    accepted, but upon download will be named ‘index.php.html’, which no longer matches,
    and so thefile will be deleted.
    • Query strings do not contribute to URL matching, but are included in local filenames, and
    so do contribute to filename matching.
    This behavior, too, is considered less-than-desirable, and may change in a future version of
    Wget.
    4.3 Directory-Based Limits
    Regardless of other link-following facilities, it is often useful to place the restriction of what files
    to retrieve based on the directories those files are placed in. There can be many reasons for
    this—the home pages may be organized in a reasonable directory structure; or some directories
    may contain useless information, e.g. ‘/cgi-bin’ or ‘/dev’ directories.
    Wget offers three different options to deal with this requirement. Each option description
    lists a short name, a long name, and the equivalent command in ‘.wgetrc’.
    ‘-I list’
    ‘--include list’
    ‘include_directories = list’
    ‘-I’ option accepts a comma-separated list of directories included in the retrieval.
    Any other directories will simply be ignored. The directories are absolute paths.
    So, if you wish to download from ‘http://host/people/bozo/’ following only links
    to bozo’s colleagues in the ‘/people’ directory and the bogus scripts in ‘/cgi-bin’,
    you can specify:
    wget -I /people,/cgi-bin http://host/people/bozo/
    ‘-X list’
    ‘--exclude list’
    ‘exclude_directories = list’
    ‘-X’ option is exactly the reverse of ‘-I’—this is a list of directories excluded from
    the download. E.g. if you do not want Wget to download things from ‘/cgi-bin’
    directory, specify ‘-X /cgi-bin’ on the command line.
    The same as with ‘-A’/‘-R’, these two options can be combined to get a better fine-
    tuning of downloading subdirectories. E.g. if you want to load all the files from
    ‘/pub’ hierarchy except for ‘/pub/worthless’, specify ‘-I/pub -X/pub/worthless’.
    ‘-np’
    ‘--no-parent’
    ‘no_parent = on’
    The simplest, and often very useful way of limiting directories is disallowing retrieval
    of the links that refer to the hierarchy above than the beginning directory, i.e.
    disallowing ascent to the parent directory/directories.
    The ‘--no-parent’ option (short ‘-np’) is useful in this case. Using it guarantees
    that you will never leave the existing hierarchy. Supposing you issue Wget with:
    wget -r --no-parent http://somehost/~luzer/my-archive/
    Chapter 4: Following Links 35
    You may rest assured that none of the references to ‘/~his-girls-homepage/’
    or ‘/~luzer/all-my-mpegs/’ will be followed. Only the archive you are
    interested in will be downloaded. Essentially, ‘--no-parent’ is similar to
    ‘-I/~luzer/my-archive’, only it handles redirections in a more intelligent fashion.
    Note that, for HTTP (and HTTPS), the trailing slash is very important to
    ‘--no-parent’. HTTP has no concept of a “directory”—Wget relies on you to
    indicate what’s a directory and what isn’t. In ‘http://foo/bar/’, Wget will con-
    sider ‘bar’ to be a directory, while in ‘http://foo/bar’ (no trailing slash), ‘bar’
    will be considered a filename (so ‘--no-parent’ would be meaningless, as its parent
    is ‘/’).
    4.4 Relative Links
    When ‘-L’ is turned on, only the relative links are ever followed. Relative links are here defined
    those that do not refer to the web server root. For example, these links are relative:



    These links are not relative:



    Using this option guarantees that recursive retrieval will not span hosts, even without ‘-H’.
    In simple cases it also allows downloads to “just work” without having to convert links.
    This option is probably not very useful and might be removed in a future release.
    4.5 Following FTP Links
    The rules for ftp are somewhat specific, as it is necessary for them to be. ftp links in html
    documents are often included for purposes of reference, and it is often inconvenient to download
    them by default.
    To have ftp links followed from html documents, you need to specify the ‘--follow-ftp’
    option. Having done that, ftp links will span hosts regardless of ‘-H’ setting. This is logical, as
    ftp links rarely point to the same host where the http server resides. For similar reasons, the
    ‘-L’ options has no effect on such downloads. On the other hand, domain acceptance (‘-D’) and
    suffix rules (‘-A’ and ‘-R’) apply normally.
    Also note that followed links to ftp directories will not be retrieved recursively further.
    Chapter 5: Time-Stamping 36
    5 Time-Stamping
    One of the most important aspects of mirroring information from the Internet is updating your
    archives.
    Downloading the whole archive again and again, just to replace a few changed files is expen-
    sive, both in terms of wasted bandwidth and money, and the time to do the update. This is
    why all the mirroring tools offer the option of incremental updating.
    Such an updating mechanism means that the remote server is scanned in search of new files.
    Only those new files will be downloaded in the place of the old ones.
    A file is considered new if one of these two conditions are met:
  • A file of that name does not already exist locally.
  • A file of that name does exist, but the remote file was modified more recently than the local
    file.
    To implement this, the program needs to be aware of the time of last modification of both
    local and remote files. We call this information the time-stamp of a file.
    The time-stamping in GNU Wget is turned on using ‘--timestamping’ (‘-N’) option, or
    through timestamping = on directive in ‘.wgetrc’. With this option, for each file it intends
    to download, Wget will check whether a local file of the same name exists. If it does, and the
    remote file is not newer, Wget will not download it.
    If the local file does not exist, or the sizes of the files do not match, Wget will download the
    remote file no matter what the time-stamps say.
    5.1 Time-Stamping Usage
    The usage of time-stamping is simple. Say you would like to download a file so that it keeps its
    date of modification.
    wget -S http://www.gnu.ai.mit.edu/
    A simple ls -l shows that the time stamp on the local file equals the state of the Last-
    Modified header, as returned by the server. As you can see, the time-stamping info is preserved
    locally, even without ‘-N’ (at least for http).
    Several days later, you would like Wget to check if the remote file has changed, and download
    it if it has.
    wget -N http://www.gnu.ai.mit.edu/
    Wget will ask the server for the last-modified date. If the local file has the same timestamp
    as the server, or a newer one, the remote file will not be re-fetched. However, if the remote file
    is more recent, Wget will proceed to fetch it.
    The same goes for ftp. For example:
    wget "ftp://ftp.ifi.uio.no/pub/emacs/gnus/"
    (The quotes around that URL are to prevent the shell from trying to interpret the ‘
    ’.)
    After download, a local directory listing will show that the timestamps match those on the
    remote server. Reissuing the command with ‘-N’ will make Wget re-fetch only the files that
    have been modified since the last download.
    If you wished to mirror the GNU archive every week, you would use a command like the
    following, weekly:
    wget --timestamping -r ftp://ftp.gnu.org/pub/gnu/
    Note that time-stamping will only work for files for which the server gives a timestamp.
    For http, this depends on getting a Last-Modified header. For ftp, this depends on getting
    a directory listing with dates in a format that Wget can parse (see hundefinedi [FTP Time-
    Stamping Internals], page hundefinedi).
    Chapter 5: Time-Stamping 37
    5.2 HTTP Time-Stamping Internals
    Time-stamping in http is implemented by checking of the Last-Modified header. If you wish
    to retrieve the file ‘foo.html’ through http, Wget will check whether ‘foo.html’ exists locally.
    If it doesn’t, ‘foo.html’ will be retrieved unconditionally.
    If the file does exist locally, Wget will first check its local time-stamp (similar to the way ls
    -l checks it), and then send a HEAD request to the remote server, demanding the information
    on the remote file.
    The Last-Modified header is examined to find which file was modified more recently (which
    makes it “newer”). If the remote file is newer, it will be downloaded; if it is older, Wget will
    give up. 1
    When ‘--backup-converted’ (‘-K’) is specified in conjunction with ‘-N’, server file ‘X’ is
    compared to local file ‘X.orig’, if extant, rather than being compared to local file ‘X’, which
    will always differ if it’s been converted by ‘--convert-links’ (‘-k’).
    Arguably, http time-stamping should be implemented using the If-Modified-Since re-
    quest.
    5.3 FTP Time-Stamping Internals
    In theory, ftp time-stamping works much the same as http, only ftp has no headers—time-
    stamps must be ferreted out of directory listings.
    If an ftp download is recursive or uses globbing, Wget will use the ftp LIST command to
    get a file listing for the directory containing the desired file(s). It will try to analyze the listing,
    treating it like Unix ls -l output, extracting the time-stamps. The rest is exactly the same as
    for http. Note that when retrieving individual files from an ftp server without using globbing
    or recursion, listing files will not be downloaded (and thus files will not be time-stamped) unless
    ‘-N’ is specified.
    Assumption that every directory listing is a Unix-style listing may sound extremely con-
    straining, but in practice it is not, as many non-Unix ftp servers use the Unixoid listing format
    because most (all?) of the clients understand it. Bear in mind that rfc959 defines no standard
    way to get a file list, let alone the time-stamps. We can only hope that a future standard will
    define this.
    Another non-standard solution includes the use of MDTM command that is supported by some
    ftp servers (including the popular wu-ftpd), which returns the exact time of the specified file.
    Wget may support this command in the future.
    1
    As an additional check, Wget will look at the Content-Length header, and compare the sizes; if they are not
    the same, the remote file will be downloaded no matter what the time-stamp says.
    Chapter 6: Startup File 38
    6 Startup File
    Once you know how to change default settings of Wget through command line arguments, you
    may wish to make some of those settings permanent. You can do that in a convenient way by
    creating the Wget startup file—‘.wgetrc’.
    Besides ‘.wgetrc’ is the “main” initialization file, it is convenient to have a special facility
    for storing passwords. Thus Wget reads and interprets the contents of ‘$HOME/.netrc’, if it
    finds it. You can find ‘.netrc’ format in your system manuals.
    Wget reads ‘.wgetrc’ upon startup, recognizing a limited set of commands.
    6.1 Wgetrc Location
    When initializing, Wget will look for a global startup file, ‘/usr/local/etc/wgetrc’ by default
    (or some prefix other than ‘/usr/local’, if Wget was not installed there) and read commands
    from there, if it exists.
    Then it will look for the user’s file. If the environmental variable WGETRC is set, Wget will
    try to load that file. Failing that, no further attempts will be made.
    If WGETRC is not set, Wget will try to load ‘$HOME/.wgetrc’.
    The fact that user’s settings are loaded after the system-wide ones means that in case of col-
    lision user’s wgetrc overrides the system-wide wgetrc (in ‘/usr/local/etc/wgetrc’ by default).
    Fascist admins, away!
    6.2 Wgetrc Syntax
    The syntax of a wgetrc command is simple:
    variable = value
    The variable will also be called command. Valid values are different for different commands.
    The commands are case-, underscore- and minus-insensitive. Thus ‘DIr__PrefiX’,
    ‘DIr-PrefiX’ and ‘dirprefix’ are the same. Empty lines, lines beginning with ‘#’ and lines
    containing white-space only are discarded.
    Commands that expect a comma-separated list will clear the list on an empty command. So,
    if you wish to reset the rejection list specified in global ‘wgetrc’, you can do it with:
    reject =
    6.3 Wgetrc Commands
    The complete set of commands is listed below. Legal values are listed after the ‘=’. Simple
    Boolean values can be set or unset using ‘on’ and ‘off’ or ‘1’ and ‘0’.
    Some commands take pseudo-arbitrary values. address values can be hostnames or dotted-
    quad IP addresses. n can be any positive integer, or ‘inf’ for infinity, where appropriate. string
    values can be any non-empty string.
    Most of these commands have direct command-line equivalents. Also, any wgetrc command
    can be specified on the command line using the ‘--execute’ switch (see hundefinedi [Basic
    Startup Options], page hundefinedi.)
    accept/reject = string
    Same as ‘-A’/‘-R’ (see hundefinedi [Types of Files], page hundefinedi).
    add hostdir = on/off
    Enable/disable host-prefixed file names. ‘-nH’ disables it.
    Chapter 6: Startup File 39
    ask password = on/off
    Prompt for a password for each connection established. Cannot be specified when
    ‘--password’ is being used, because they are mutually exclusive. Equivalent to
    ‘--ask-password’.
    auth no challenge = on/off
    If this option is given, Wget will send Basic HTTP authentication information
    (plaintext username and password) for all requests. See ‘--auth-no-challenge’.
    background = on/off
    Enable/disable going to background—the same as ‘-b’ (which enables it).
    backup converted = on/off
    Enable/disable saving pre-converted files with the suffix ‘.orig’—the same as ‘-K’
    (which enables it).
    backups = number
    Use up to number backups for a file. Backups are rotated by adding an incremental
    counter that starts at ‘1’. The default is ‘0’.
    base = string
    Consider relative urls in input files (specified via the ‘input’ command or the
    ‘--input-file’/‘-i’ option, together with ‘force_html’ or ‘--force-html’) as be-
    ing relative to string—the same as ‘--base=string’.
    bind address = address
    Bind to address, like the ‘--bind-address=address’.
    ca certificate = file
    Set the certificate authority bundle file to file. The same as
    ‘--ca-certificate=file’.
    ca directory = directory
    Set the directory used for certificate authorities. The same as
    ‘--ca-directory=directory’.
    cache = on/off
    When set to off, disallow server-caching. See the ‘--no-cache’ option.
    certificate = file
    Set the client certificate file name to file. The same as ‘--certificate=file’.
    certificate type = string
    Specify the type of the client certificate, legal values being ‘PEM’ (the default) and
    ‘DER’ (aka ASN1). The same as ‘--certificate-type=string’.
    check certificate = on/off
    If this is set to off, the server certificate is not checked against the specified client
    authorities. The default is “on”. The same as ‘--check-certificate’.
    connect timeout = n
    Set the connect timeout—the same as ‘--connect-timeout’.
    content disposition = on/off
    Turn on recognition of the (non-standard) ‘Content-Disposition’ HTTP header—
    if set to ‘on’, the same as ‘--content-disposition’.
    trust server names = on/off
    If set to on, use the last component of a redirection URL for the local file name.
    Chapter 6: Startup File 40
    continue = on/off
    If set to on, force continuation of preexistent partially retrieved files. See ‘-c’ before
    setting it.
    convert links = on/off
    Convert non-relative links locally. The same as ‘-k’.
    cookies = on/off
    When set to off, disallow cookies. See the ‘--cookies’ option.
    cut dirs = n
    Ignore n remote directory components. Equivalent to ‘--cut-dirs=n’.
    debug = on/off
    Debug mode, same as ‘-d’.
    default page = string
    Default page name—the same as ‘--default-page=string’.
    delete after = on/off
    Delete after download—the same as ‘--delete-after’.
    dir prefix = string
    Top of directory tree—the same as ‘-P string’.
    dirstruct = on/off
    Turning dirstruct on or off—the same as ‘-x’ or ‘-nd’, respectively.
    dns cache = on/off
    Turn DNS caching on/off. Since DNS caching is on by default, this option is nor-
    mally used to turn it off and is equivalent to ‘--no-dns-cache’.
    dns timeout = n
    Set the DNS timeout—the same as ‘--dns-timeout’.
    domains = string
    Same as ‘-D’ (see hundefinedi [Spanning Hosts], page hundefinedi).
    dot bytes = n
    Specify the number of bytes “contained” in a dot, as seen throughout the retrieval
    (1024 by default). You can postfix the value with ‘k’ or ‘m’, representing kilobytes
    and megabytes, respectively. With dot settings you can tailor the dot retrieval to
    suit your needs, or you can use the predefined styles (see hundefinedi [Download
    Options], page hundefinedi).
    dot spacing = n
    Specify the number of dots in a single cluster (10 by default).
    dots in line = n
    Specify the number of dots that will be printed in each line throughout the retrieval
    (50 by default).
    egd file = file
    Use string as the EGD socket file name. The same as ‘--egd-file=file’.
    exclude directories = string
    Specify a comma-separated list of directories you wish to exclude from download—
    the same as ‘-X string’ (see hundefinedi [Directory-Based Limits], page hunde-
    finedi).
    exclude domains = string
    Same as ‘--exclude-domains=string’ (see hundefinedi [Spanning Hosts], page hun-
    definedi).
    Chapter 6: Startup File 41
    follow ftp = on/off
    Follow ftp links from html documents—the same as ‘--follow-ftp’.
    follow tags = string
    Only follow certain html tags when doing a recursive retrieval, just like
    ‘--follow-tags=string’.
    force html = on/off
    If set to on, force the input filename to be regarded as an html document—the
    same as ‘-F’.
    ftp password = string
    Set your ftp password to string. Without this setting, the password defaults to
    ‘-wget@’, which is a useful default for anonymous ftp access.
    This command used to be named passwd prior to Wget 1.10.
    ftp proxy = string
    Use string as ftp proxy, instead of the one specified in environment.
    ftp user = string
    Set ftp user to string.
    This command used to be named login prior to Wget 1.10.
    glob = on/off
    Turn globbing on/off—the same as ‘--glob’ and ‘--no-glob’.
    header = string
    Define a header for HTTP downloads, like using ‘--header=string’.
    adjust extension = on/off
    Add a ‘.html’ extension to ‘text/html’ or ‘application/xhtml+xml’ files that lack
    one, or a ‘.css’ extension to ‘text/css’ files that lack one, like ‘-E’. Previously
    named ‘html_extension’ (still acceptable, but deprecated).
    http keep alive = on/off
    Turn the keep-alive feature on or off (defaults to on). Turning it off is equivalent to
    ‘--no-http-keep-alive’.
    http password = string
    Set http password, equivalent to ‘--http-password=string’.
    http proxy = string
    Use string as http proxy, instead of the one specified in environment.
    http user = string
    Set http user to string, equivalent to ‘--http-user=string’.
    https only = on/off
    When in recursive mode, only HTTPS links are followed (defaults to off).
    https proxy = string
    Use string as https proxy, instead of the one specified in environment.
    ignore case = on/off
    When set to on, match files and directories case insensitively; the same as
    ‘--ignore-case’.
    ignore length = on/off
    When set to on, ignore Content-Length header; the same as ‘--ignore-length’.
    Chapter 6: Startup File 42
    ignore tags = string
    Ignore certain html tags when doing a recursive retrieval, like
    ‘--ignore-tags=string’.
    include directories = string
    Specify a comma-separated list of directories you wish to follow when downloading—
    the same as ‘-I string’.
    iri = on/off
    When set to on, enable internationalized URI (IRI) support; the same as ‘--iri’.
    inet4 only = on/off
    Force connecting to IPv4 addresses, off by default. You can put this in the global
    init file to disable Wget’s attempts to resolve and connect to IPv6 hosts. Available
    only if Wget was compiled with IPv6 support. The same as ‘--inet4-only’ or ‘-4’.
    inet6 only = on/off
    Force connecting to IPv6 addresses, off by default. Available only if Wget was
    compiled with IPv6 support. The same as ‘--inet6-only’ or ‘-6’.
    input = file
    Read the urls from string, like ‘-i file’.
    keep session cookies = on/off
    When specified, causes ‘save_cookies = on’ to also save session cookies. See
    ‘--keep-session-cookies’.
    limit rate = rate
    Limit the download speed to no more than rate bytes per second. The same as
    ‘--limit-rate=rate’.
    load cookies = file
    Load cookies from file. See ‘--load-cookies file’.
    local encoding = encoding
    Force Wget to use encoding as the default system encoding. See
    ‘--local-encoding’.
    logfile = file
    Set logfile to file, the same as ‘-o file’.
    max redirect = number
    Specifies the maximum number of redirections to follow for a resource. See
    ‘--max-redirect=number’.
    mirror = on/off
    Turn mirroring on/off. The same as ‘-m’.
    netrc = on/off
    Turn reading netrc on or off.
    no clobber = on/off
    Same as ‘-nc’.
    no parent = on/off
    Disallow retrieving outside the directory hierarchy, like ‘--no-parent’ (see hunde-
    finedi [Directory-Based Limits], page hundefinedi).
    no proxy = string
    Use string as the comma-separated list of domains to avoid in proxy loading, instead
    of the one specified in environment.
    Chapter 6: Startup File 43
    output document = file
    Set the output filename—the same as ‘-O file’.
    page requisites = on/off
    Download all ancillary documents necessary for a single html page to display
    properly—the same as ‘-p’.
    passive ftp = on/off
    Change setting of passive ftp, equivalent to the ‘--passive-ftp’ option.
    password = string
    Specify password string for both ftp and http file retrieval. This command can be
    overridden using the ‘ftp_password’ and ‘http_password’ command for ftp and
    http respectively.
    post data = string
    Use POST as the method for all HTTP requests and send string in the request
    body. The same as ‘--post-data=string’.
    post file = file
    Use POST as the method for all HTTP requests and send the contents of file in the
    request body. The same as ‘--post-file=file’.
    prefer family = none/IPv4/IPv6
    When given a choice of several addresses, connect to the addresses with specified
    address family first. The address order returned by DNS is used without change by
    default. The same as ‘--prefer-family’, which see for a detailed discussion of why
    this is useful.
    private key = file
    Set the private key file to file. The same as ‘--private-key=file’.
    private key type = string
    Specify the type of the private key, legal values being ‘PEM’ (the default) and ‘DER’
    (aka ASN1). The same as ‘--private-type=string’.
    progress = string
    Set the type of the progress indicator. Legal types are ‘dot’ and ‘bar’. Equivalent
    to ‘--progress=string’.
    protocol directories = on/off
    When set, use the protocol name as a directory component of local file names. The
    same as ‘--protocol-directories’.
    proxy password = string
    Set proxy authentication password to string, like ‘--proxy-password=string’.
    proxy user = string
    Set proxy authentication user name to string, like ‘--proxy-user=string’.
    quiet = on/off
    Quiet mode—the same as ‘-q’.
    quota = quota
    Specify the download quota, which is useful to put in the global ‘wgetrc’. When
    download quota is specified, Wget will stop retrieving after the download sum has
    become greater than quota. The quota can be specified in bytes (default), kbytes
    ‘k’ appended) or mbytes (‘m’ appended). Thus ‘quota = 5m’ will set the quota to 5
    megabytes. Note that the user’s startup file overrides system settings.
    Chapter 6: Startup File 44
    random file = file
    Use file as a source of randomness on systems lacking ‘/dev/random’.
    random wait = on/off
    Turn random between-request wait times on or off. The same as ‘--random-wait’.
    read timeout = n
    Set the read (and write) timeout—the same as ‘--read-timeout=n’.
    reclevel = n
    Recursion level (depth)—the same as ‘-l n’.
    recursive = on/off
    Recursive on/off—the same as ‘-r’.
    referer = string
    Set HTTP ‘Referer:’ header just like ‘--referer=string’. (Note that it was the
    folks who wrote the http spec who got the spelling of “referrer” wrong.)
    relative only = on/off
    Follow only relative links—the same as ‘-L’ (see hundefinedi [Relative Links],
    page hundefinedi).
    remote encoding = encoding
    Force Wget to use encoding as the default remote server encoding. See
    ‘--remote-encoding’.
    remove listing = on/off
    If set to on, remove ftp listings downloaded by Wget. Setting it to off is the same
    as ‘--no-remove-listing’.
    restrict file names = unix/windows
    Restrict the file names generated by Wget from URLs. See
    ‘--restrict-file-names’ for a more detailed description.
    retr symlinks = on/off
    When set to on, retrieve symbolic links as if they were plain files; the same as
    ‘--retr-symlinks’.
    retry connrefused = on/off
    When set to on, consider “connection refused” a transient error—the same as
    ‘--retry-connrefused’.
    robots = on/off
    Specify whether the norobots convention is respected by Wget, “on” by default.
    This switch controls both the ‘/robots.txt’ and the ‘nofollow’ aspect of the spec.
    See hundefinedi [Robot Exclusion], page hundefinedi, for more details about this.
    Be sure you know what you are doing before turning this off.
    save cookies = file
    Save cookies to file. The same as ‘--save-cookies file’.
    save headers = on/off
    Same as ‘--save-headers’.
    secure protocol = string
    Choose the secure protocol to be used. Legal values are ‘auto’ (the default), ‘SSLv2’,
    ‘SSLv3’, and ‘TLSv1’. The same as ‘--secure-protocol=string’.
    server response = on/off
    Choose whether or not to print the http and ftp server responses—the same as
    ‘-S’.
    Chapter 6: Startup File 45
    show all dns entries = on/off
    When a DNS name is resolved, show all the IP addresses, not just the first three.
    span hosts = on/off
    Same as ‘-H’.
    spider = on/off
    Same as ‘--spider’.
    strict comments = on/off
    Same as ‘--strict-comments’.
    timeout = n
    Set all applicable timeout values to n, the same as ‘-T n’.
    timestamping = on/off
    Turn timestamping on/off. The same as ‘-N’ (see hundefinedi [Time-Stamping],
    page hundefinedi).
    use server timestamps = on/off
    If set to ‘off’, Wget won’t set the local file’s timestamp by the one on the server
    (same as ‘--no-use-server-timestamps’).
    tries = n Set number of retries per url—the same as ‘-t n’.
    use proxy = on/off
    When set to off, don’t use proxy even when proxy-related environment variables are
    set. In that case it is the same as using ‘--no-proxy’.
    user = string
    Specify username string for both ftp and http file retrieval. This command can
    be overridden using the ‘ftp_user’ and ‘http_user’ command for ftp and http
    respectively.
    user agent = string
    User agent identification sent to the HTTP Server—the same as
    ‘--user-agent=string’.
    verbose = on/off
    Turn verbose on/off—the same as ‘-v’/‘-nv’.
    wait = n Wait n seconds between retrievals—the same as ‘-w n’.
    wait retry = n
    Wait up to n seconds between retries of failed retrievals only—the same as
    ‘--waitretry=n’. Note that this is turned on by default in the global ‘wgetrc’.
    6.4 Sample Wgetrc
    This is the sample initialization file, as given in the distribution. It is divided in two section—
    one for global usage (suitable for global startup file), and one for local usage (suitable for
    ‘$HOME/.wgetrc’). Be careful about the things you change.
    Note that almost all the lines are commented out. For a command to have any effect, you
    must remove the ‘#’ character at the beginning of its line.

    #

    Sample Wget initialization file .wgetrc

    #

    You can use this file to change the default behaviour of wget or to

    Chapter 6: Startup File 46

    avoid having to type many many command-line options. This file does

    not contain a comprehensive list of commands -- look at the manual

    to find out what you can put into this file. You can find this here:

    $ info wget.info ’Startup File’

    Or online here:

    https://www.gnu.org/software/wget/manual/wget.html#Startup-File

    #

    Wget initialization file can reside in /usr/local/etc/wgetrc

    (global, for all users) or $HOME/.wgetrc (for a single user).

    #

    To use the settings in this file, you will have to uncomment them,

    as well as change them, in most cases, as the values on the

    commented-out lines are the default values (e.g. "off").

    #

    Command are case-, underscore- and minus-insensitive.

    For example ftp_proxy, ftp-proxy and ftpproxy are the same.

    #

    Global settings (useful for setting up in /usr/local/etc/wgetrc).

    Think well before you change them, since they may reduce wget’s

    functionality, and make it behave contrary to the documentation:

    #

    You can set retrieve quota for beginners by specifying a value

    optionally followed by ’K’ (kilobytes) or ’M’ (megabytes). The

    default quota is unlimited.

    quota = inf

    You can lower (or raise) the default number of retries when

    downloading a file (default is 20).

    tries = 20

    Lowering the maximum depth of the recursive retrieval is handy to

    prevent newbies from going too "deep" when they unwittingly start

    the recursive retrieval. The default is 5.

    reclevel = 5

    By default Wget uses "passive FTP" transfer where the client

    initiates the data connection to the server rather than the other

    way around. That is required on systems behind NAT where the client

    computer cannot be easily reached from the Internet. However, some

    firewalls software explicitly supports active FTP and in fact has

    problems supporting passive transfer. If you are in such

    environment, use "passive_ftp = off" to revert to active FTP.

    passive_ftp = off

    The "wait" command below makes Wget wait between every connection.

    If, instead, you want Wget to wait only between retries of failed

    downloads, set waitretry to maximum number of seconds to wait (Wget

    will use "linear backoff", waiting 1 second after the first failure

    on a file, 2 seconds after the second failure, etc. up to this max).

    Chapter 6: Startup File 47

    waitretry = 10

    #

    Local settings (for a user to set in his $HOME/.wgetrc). It is

    highly undesirable to put these settings in the global file, since

    they are potentially dangerous to "normal" users.

    #

    Even when setting up your own ~/.wgetrc, you should know what you

    are doing before doing so.

    #

    Set this to on to use timestamping by default:

    timestamping = off

    It is a good idea to make Wget send your email address in a ‘From:’

    header with your request (so that server administrators can contact

    you in case of errors). Wget does not send ‘From:’ by default.

    header = From: Your Name username@site.domain

    You can set up other headers, like Accept-Language. Accept-Language

    is not sent by default.

    header = Accept-Language: en

    You can set the default proxies for Wget to use for http, https, and ftp.

    They will override the value in the environment.

    https_proxy = http://proxy.yoyodyne.com:18023/

    http_proxy = http://proxy.yoyodyne.com:18023/

    ftp_proxy = http://proxy.yoyodyne.com:18023/

    If you do not want to use proxy at all, set this to off.

    use_proxy = on

    You can customize the retrieval outlook. Valid options are default,

    binary, mega and micro.

    dot_style = default

    Setting this to off makes Wget not download /robots.txt. Be sure to

    know exactly what /robots.txt is and how it is used before changing

    the default!

    robots = on

    It can be useful to make Wget wait between connections. Set this to

    the number of seconds you want Wget to wait.

    wait = 0

    You can force creating directory structure, even if a single is being

    retrieved, by setting this to on.

    dirstruct = off

    You can turn on recursive retrieving by default (don’t do this if

    you are not sure you know what it means) by setting this to on.

    Chapter 6: Startup File 48

    recursive = off

    To always back up file X as X.orig before converting its links (due

    to -k / --convert-links / convert_links = on having been specified),

    set this variable to on:

    backup_converted = off

    To have Wget follow FTP links from HTML files by default, set this

    to on:

    follow_ftp = off

    To try ipv6 addresses first:

    prefer-family = IPv6

    Set default IRI support state

    iri = off

    Force the default system encoding

    localencoding = UTF-8

    Force the default remote server encoding

    remoteencoding = UTF-8

    Turn on to prevent following non-HTTPS links when in recursive mode

    httpsonly = off

    Tune HTTPS security (auto, SSLv2, SSLv3, TLSv1, PFS)

    secureprotocol = auto

    Chapter 7: Examples 49
    7 Examples
    The examples are divided into three sections loosely based on their complexity.
    7.1 Simple Usage
    • Say you want to download a url. Just type:
    wget http://fly.srk.fer.hr/
    • But what will happen if the connection is slow, and the file is lengthy? The connection will
    probably fail before the whole file is retrieved, more than once. In this case, Wget will try
    getting the file until it either gets the whole of it, or exceeds the default number of retries
    (this being 20). It is easy to change the number of tries to 45, to insure that the whole file
    will arrive safely:
    wget --tries=45 http://fly.srk.fer.hr/jpg/flyweb.jpg
    • Now let’s leave Wget to work in the background, and write its progress to log file ‘log’. It
    is tiring to type ‘--tries’, so we shall use ‘-t’.
    wget -t 45 -o log http://fly.srk.fer.hr/jpg/flyweb.jpg &
    The ampersand at the end of the line makes sure that Wget works in the background. To
    unlimit the number of retries, use ‘-t inf’.
    • The usage of ftp is as simple. Wget will take care of login and password.
    wget ftp://gnjilux.srk.fer.hr/welcome.msg
    • If you specify a directory, Wget will retrieve the directory listing, parse it and convert it to
    html. Try:
    wget ftp://ftp.gnu.org/pub/gnu/
    links index.html
    7.2 Advanced Usage
    • You have a file that contains the URLs you want to download? Use the ‘-i’ switch:
    wget -i file
    If you specify ‘-’ as file name, the urls will be read from standard input.
    • Create a five levels deep mirror image of the GNU web site, with the same directory structure
    the original has, with only one try per document, saving the log of the activities to ‘gnulog’:
    wget -r http://www.gnu.org/ -o gnulog
    • The same as the above, but convert the links in the downloaded files to point to local files,
    so you can view the documents off-line:
    wget --convert-links -r http://www.gnu.org/ -o gnulog
    • Retrieve only one html page, but make sure that all the elements needed for the page to be
    displayed, such as inline images and external style sheets, are also downloaded. Also make
    sure the downloaded page references the downloaded links.
    wget -p --convert-links http://www.server.com/dir/page.html
    The html page will be saved to ‘www.server.com/dir/page.html’, and the images,
    stylesheets, etc., somewhere under ‘www.server.com/’, depending on where they were on
    the remote server.
    • The same as the above, but without the ‘www.server.com/’ directory. In fact, I don’t
    want to have all those random server directories anyway—just save all those files under a
    ‘download/’ subdirectory of the current directory.
    wget -p --convert-links -nH -nd -Pdownload \
    http://www.server.com/dir/page.html
    Chapter 7: Examples 50
    • Retrieve the index.html of ‘www.lycos.com’, showing the original server headers:
    wget -S http://www.lycos.com/
    • Save the server headers with the file, perhaps for post-processing.
    wget --save-headers http://www.lycos.com/
    more index.html
    • Retrieve the first two levels of ‘wuarchive.wustl.edu’, saving them to ‘/tmp’.
    wget -r -l2 -P/tmp ftp://wuarchive.wustl.edu/
    • You want to download all the gifs from a directory on an http server. You tried ‘wget
    http://www.server.com/dir/.gif’, but that didn’t work because http retrieval does
    not support globbing. In that case, use:
    wget -r -l1 --no-parent -A.gif http://www.server.com/dir/
    More verbose, but the effect is the same. ‘-r -l1’ means to retrieve recursively (see hunde-
    finedi [Recursive Download], page hundefinedi), with maximum depth of 1. ‘--no-parent’
    means that references to the parent directory are ignored (see hundefinedi [Directory-Based
    Limits], page hundefinedi), and ‘-A.gif’ means to download only the gif files. ‘-A "
    .gif"’
    would have worked too.
    • Suppose you were in the middle of downloading, when Wget was interrupted. Now you do
    not want to clobber the files already present. It would be:
    wget -nc -r http://www.gnu.org/
    • If you want to encode your own username and password to http or ftp, use the appropriate
    url syntax (see hundefinedi [URL Format], page hundefinedi).
    wget ftp://hniksic:mypassword@unix.server.com/.emacs
    Note, however, that this usage is not advisable on multi-user systems because it reveals
    your password to anyone who looks at the output of ps.
    • You would like the output documents to go to standard output instead of to files?
    wget -O - http://jagor.srce.hr/ http://www.srce.hr/
    You can also combine the two options and make pipelines to retrieve the documents from
    remote hotlists:
    wget -O - http://cool.list.com/ | wget --force-html -i -
    7.3 Very Advanced Usage
    • If you wish Wget to keep a mirror of a page (or ftp subdirectories), use ‘--mirror’ (‘-m’),
    which is the shorthand for ‘-r -l inf -N’. You can put Wget in the crontab file asking it
    to recheck a site each Sunday:
    crontab
    0 0 0 wget --mirror http://www.gnu.org/ -o /home/me/weeklog
    • In addition to the above, you want the links to be converted for local viewing. But, after
    having read this manual, you know that link conversion doesn’t play well with timestamping,
    so you also want Wget to back up the original html files before the conversion. Wget
    invocation would look like this:
    wget --mirror --convert-links --backup-converted \
    http://www.gnu.org/ -o /home/me/weeklog
    • But you’ve also noticed that local viewing doesn’t work all that well when html files
    are saved under extensions other than ‘.html’, perhaps because they were served as
    ‘index.cgi’. So you’d like Wget to rename all the files served with content-type ‘text/html’
    or ‘application/xhtml+xml’ to ‘name.html’.
    Chapter 7: Examples 51
    wget --mirror --convert-links --backup-converted \
    --html-extension -o /home/me/weeklog \
    http://www.gnu.org/
    Or, with less typing:
    wget -m -k -K -E http://www.gnu.org/ -o /home/me/weeklog
    Chapter 8: Various 52
    8 Various
    This chapter contains all the stuff that could not fit anywhere else.
    8.1 Proxies
    Proxies are special-purpose http servers designed to transfer data from remote servers to local
    clients. One typical use of proxies is lightening network load for users behind a slow connection.
    This is achieved by channeling all http and ftp requests through the proxy which caches the
    transferred data. When a cached resource is requested again, proxy will return the data from
    cache. Another use for proxies is for companies that separate (for security reasons) their internal
    networks from the rest of Internet. In order to obtain information from the Web, their users
    connect and retrieve remote data using an authorized proxy.
    Wget supports proxies for both http and ftp retrievals. The standard way to specify proxy
    location, which Wget recognizes, is using the following environment variables:
    http_proxy
    https_proxy
    If set, the http_proxy and https_proxy variables should contain the urls of the
    proxies for http and https connections respectively.
    ftp_proxy
    This variable should contain the url of the proxy for ftp connections. It is quite
    common that http_proxy and ftp_proxy are set to the same url.
    no_proxy This variable should contain a comma-separated list of domain extensions proxy
    should not be used for. For instance, if the value of no_proxy is ‘.mit.edu’, proxy
    will not be used to retrieve documents from MIT.
    In addition to the environment variables, proxy location and settings may be specified from
    within Wget itself.
    ‘--no-proxy’
    ‘proxy = on/off’
    This option and the corresponding command may be used to suppress the use of
    proxy, even if the appropriate environment variables are set.
    ‘http_proxy = URL’
    ‘https_proxy = URL’
    ‘ftp_proxy = URL’
    ‘no_proxy = string’
    These startup file variables allow you to override the proxy settings specified by the
    environment.
    Some proxy servers require authorization to enable you to use them. The authorization
    consists of username and password, which must be sent by Wget. As with http authorization,
    several authentication schemes exist. For proxy authorization only the Basic authentication
    scheme is currently implemented.
    You may specify your username and password either through the proxy url or through the
    command-line options. Assuming that the company’s proxy is located at ‘proxy.company.com’
    at port 8001, a proxy url location containing authorization data might look like this:
    http://hniksic:mypassword@proxy.company.com:8001/
    Alternatively, you may use the ‘proxy-user’ and ‘proxy-password’ options, and the equiv-
    alent ‘.wgetrc’ settings proxy_user and proxy_password to set the proxy username and pass-
    word.
    Chapter 8: Various 53
    8.2 Distribution
    Like all GNU utilities, the latest version of Wget can be found at the master GNU
    archive site ftp.gnu.org, and its mirrors. For example, Wget 1.17.1 can be found at
    ftp://ftp.gnu.org/pub/gnu/wget/wget-1.17.1.tar.gz
    8.3 Web Site
    The official web site for GNU Wget is at http://www.gnu.org/software/wget/. However,
    most useful information resides at “The Wget Wgiki”, http://wget.addictivecode.org/.
    8.4 Mailing Lists
    Primary List
    The primary mailinglist for discussion, bug-reports, or questions about GNU Wget is at
    bug-wget@gnu.org. To subscribe, send an email to bug-wget-join@gnu.org, or visit
    http://lists.gnu.org/mailman/listinfo/bug-wget.
    You do not need to subscribe to send a message to the list; however, please note that unsub-
    scribed messages are moderated, and may take a while before they hit the list—usually around
    a day. If you want your message to show up immediately, please subscribe to the list before
    posting. Archives for the list may be found at http://lists.gnu.org/pipermail/bug-wget/.
    An NNTP/Usenettish gateway is also available via Gmane. You can see the Gmane archives
    at http://news.gmane.org/gmane.comp.web.wget.general. Note that the Gmane archives
    conveniently include messages from both the current list, and the previous one. Messages also
    show up in the Gmane archives sooner than they do at lists.gnu.org.
    Bug Notices List
    Additionally, there is the wget-notify@addictivecode.org mailing list. This is a
    non-discussion list that receives bug report notifications from the bug-tracker. To
    subscribe to this list, send an email to wget-notify-join@addictivecode.org, or visit
    http://addictivecode.org/mailman/listinfo/wget-notify.
    Obsolete Lists
    Previously, the mailing list wget@sunsite.dk was used as the main discussion list, and another
    list, wget-patches@sunsite.dk was used for submitting and discussing patches to GNU Wget.
    Messages from wget@sunsite.dk are archived at
    http://www.mail-archive.com/wget%40sunsite.dk/ and at
    http://news.gmane.org/gmane.comp.web.wget.general (which also continues to archive
    the current list, bug-wget@gnu.org).
    Messages from wget-patches@sunsite.dk are archived at
    http://news.gmane.org/gmane.comp.web.wget.patches.
    8.5 Internet Relay Chat
    In addition to the mailinglists, we also have a support channel set up via IRC at
    irc.freenode.org, #wget. Come check it out!
    8.6 Reporting Bugs
    You are welcome to submit bug reports via the GNU Wget bug tracker (see
    http://wget.addictivecode.org/BugTracker).
    Before actually submitting a bug report, please try to follow a few simple guidelines.
    Chapter 8: Various 54
  • Please try to ascertain that the behavior you see really is a bug. If Wget crashes, it’s a bug.
    If Wget does not behave as documented, it’s a bug. If things work strange, but you are not
    sure about the way they are supposed to work, it might well be a bug, but you might want
    to double-check the documentation and the mailing lists (see hundefinedi [Mailing Lists],
    page hundefinedi).
  • Try to repeat the bug in as simple circumstances as possible. E.g. if Wget crashes while
    downloading ‘wget -rl0 -kKE -t5 --no-proxy http://yoyodyne.com -o /tmp/log’, you
    should try to see if the crash is repeatable, and if will occur with a simpler set of op-
    tions. You might even try to start the download at the page where the crash occurred to
    see if that page somehow triggered the crash.
    Also, while I will probably be interested to know the contents of your ‘.wgetrc’ file, just
    dumping it into the debug message is probably a bad idea. Instead, you should first try
    to see if the bug repeats with ‘.wgetrc’ moved out of the way. Only if it turns out that
    ‘.wgetrc’ settings affect the bug, mail me the relevant parts of the file.
  • Please start Wget with ‘-d’ option and send us the resulting output (or relevant parts
    thereof). If Wget was compiled without debug support, recompile it—it is much easier to
    trace bugs with debug support on.
    Note: please make sure to remove any potentially sensitive information from the debug log
    before sending it to the bug address. The -d won’t go out of its way to collect sensitive
    information, but the log will contain a fairly complete transcript of Wget’s communication
    with the server, which may include passwords and pieces of downloaded data. Since the
    bug address is publically archived, you may assume that all bug reports are visible to the
    public.
  • If Wget has crashed, try to run it in a debugger, e.g. gdb ‘which wget‘ core and type
    where to get the backtrace. This may not work if the system administrator has disabled
    core files, but it is safe to try.
    8.7 Portability
    Like all GNU software, Wget works on the GNU system. However, since it uses GNU Autoconf
    for building and configuring, and mostly avoids using “special” features of any particular Unix,
    it should compile (and work) on all common Unix flavors.
    Various Wget versions have been compiled and tested under many kinds of Unix systems,
    including GNU/Linux, Solaris, SunOS 4.x, Mac OS X, OSF (aka Digital Unix or Tru64), Ultrix,
    *BSD, IRIX, AIX, and others. Some of those systems are no longer in widespread use and may
    not be able to support recent versions of Wget. If Wget fails to compile on your system, we
    would like to know about it.
    Thanks to kind contributors, this version of Wget compiles and works on 32-bit Microsoft
    Windows platforms. It has been compiled successfully using MS Visual C++ 6.0, Watcom,
    Borland C, and GCC compilers. Naturally, it is crippled of some features available on Unix,
    but it should work as a substitute for people stuck with Windows. Note that Windows-specific
    portions of Wget are not guaranteed to be supported in the future, although this has been the
    case in practice for many years now. All questions and problems in Windows usage should
    be reported to Wget mailing list at wget@sunsite.dk where the volunteers who maintain the
    Windows-related features might look at them.
    Support for building on MS-DOS via DJGPP has been contributed by Gisle Vanem; a port
    to VMS is maintained by Steven Schweda, and is available at http://antinode.org/.
    Chapter 8: Various 55
    8.8 Signals
    Since the purpose of Wget is background work, it catches the hangup signal (SIGHUP) and
    ignores it. If the output was on standard output, it will be redirected to a file named ‘wget-log’.
    Otherwise, SIGHUP is ignored. This is convenient when you wish to redirect the output of Wget
    after having started it.
    $ wget http://www.gnus.org/dist/gnus.tar.gz &
    ...
    $ kill -HUP %%
    SIGHUP received, redirecting output to ‘wget-log’.
    Other than that, Wget will not try to interfere with signals in any way. C-c, kill -TERM
    and kill -KILL should kill it alike.
    Chapter 9: Appendices 56
    9 Appendices
    This chapter contains some references I consider useful.
    9.1 Robot Exclusion
    It is extremely easy to make Wget wander aimlessly around a web site, sucking all the available
    data in progress. ‘wget -r site’, and you’re set. Great? Not for the server admin.
    As long as Wget is only retrieving static pages, and doing it at a reasonable rate (see the
    ‘--wait’ option), there’s not much of a problem. The trouble is that Wget can’t tell the
    difference between the smallest static page and the most demanding CGI. A site I know has a
    section handled by a CGI Perl script that converts Info files to html on the fly. The script is
    slow, but works well enough for human users viewing an occasional Info file. However, when
    someone’s recursive Wget download stumbles upon the index page that links to all the Info files
    through the script, the system is brought to its knees without providing anything useful to the
    user (This task of converting Info files could be done locally and access to Info documentation
    for all installed GNU software on a system is available from the info command).
    To avoid this kind of accident, as well as to preserve privacy for documents that need to be
    protected from well-behaved robots, the concept of robot exclusion was invented. The idea is
    that the server administrators and document authors can specify which portions of the site they
    wish to protect from robots and those they will permit access.
    The most popular mechanism, and the de facto standard supported by all the major robots,
    is the “Robots Exclusion Standard” (RES) written by Martijn Koster et al. in 1994. It specifies
    the format of a text file containing directives that instruct the robots which URL paths to avoid.
    To be found by the robots, the specifications must be placed in ‘/robots.txt’ in the server root,
    which the robots are expected to download and parse.
    Although Wget is not a web robot in the strictest sense of the word, it can download large
    parts of the site without the user’s intervention to download an individual page. Because of
    that, Wget honors RES when downloading recursively. For instance, when you issue:
    wget -r http://www.server.com/
    First the index of ‘www.server.com’ will be downloaded. If Wget finds that it wants to down-
    load more documents from that server, it will request ‘http://www.server.com/robots.txt’
    and, if found, use it for further downloads. ‘robots.txt’ is loaded only once per each server.
    Until version 1.8, Wget supported the first version of the standard, written by
    Martijn Koster in 1994 and available at http://www.robotstxt.org/wc/norobots.html.
    As of version 1.8, Wget has supported the additional directives specified in the
    internet draft ‘’ titled “A Method for Web Robots
    Control”. The draft, which has as far as I know never made to an rfc, is available at
    http://www.robotstxt.org/wc/norobots-rfc.txt.
    This manual no longer includes the text of the Robot Exclusion Standard.
    The second, less known mechanism, enables the author of an individual document to specify
    whether they want the links from the file to be followed by a robot. This is achieved using the
    META tag, like this:

    This is explained in some detail at http://www.robotstxt.org/wc/meta-user.html. Wget
    supports this method of robot exclusion in addition to the usual ‘/robots.txt’ exclusion.
    If you know what you are doing and really really wish to turn off the robot exclusion, set the
    robots variable to ‘off’ in your ‘.wgetrc’. You can achieve the same effect from the command
    line using the -e switch, e.g. ‘wget -e robots=off url...’.
    Chapter 9: Appendices 57
    9.2 Security Considerations
    When using Wget, you must be aware that it sends unencrypted passwords through the network,
    which may present a security problem. Here are the main issues, and some solutions.
  • The passwords on the command line are visible using ps. The best way around it is
    to use wget -i - and feed the urls to Wget’s standard input, each on a separate line,
    terminated by C-d. Another workaround is to use ‘.netrc’ to store passwords; however,
    storing unencrypted passwords is also considered a security risk.
  • Using the insecure basic authentication scheme, unencrypted passwords are transmitted
    through the network routers and gateways.
  • The ftp passwords are also in no way encrypted. There is no good solution for this at the
    moment.
  • Although the “normal” output of Wget tries to hide the passwords, debugging logs show
    them, in all forms. This problem is avoided by being careful when you send debug logs (yes,
    even when you send them to me).
    9.3 Contributors
    GNU Wget was written by Hrvoje Nikˇ si´ c hniksic@xemacs.org,
    However, the development of Wget could never have gone as far as it has, were it not for
    the help of many people, either with bug reports, feature proposals, patches, or letters saying
    “Thanks!”.
    Special thanks goes to the following people (no particular order):
    • Dan Harkless—contributed a lot of code and documentation of extremely high quality, as
    well as the --page-requisites and related options. He was the principal maintainer for
    some time and released Wget 1.6.
    • Ian Abbott—contributed bug fixes, Windows-related fixes, and provided a prototype im-
    plementation of the breadth-first recursive download. Co-maintained Wget during the 1.8
    release cycle.
    • The dotsrc.org crew, in particular Karsten Thygesen—donated system resources such as
    the mailing list, web space, ftp space, and version control repositories, along with a lot of
    time to make these actually work. Christian Reiniger was of invaluable help with setting
    up Subversion.
    • Heiko Herold—provided high-quality Windows builds and contributed bug and build reports
    for many years.
    • Shawn McHorse—bug reports and patches.
    • Kaveh R. Ghazi—on-the-fly ansi2knr-ization. Lots of portability fixes.
    • Gordon Matzigkeit—‘.netrc’ support.
    • Zlatko
    ˇ
    Caluˇ si´ c, Tomislav Vujec and Draˇ zen Kaˇ car—feature suggestions and “philosophical”
    discussions.
    • Darko Budor—initial port to Windows.
    • Antonio Rosella—help and suggestions, plus the initial Italian translation.
    • Tomislav Petrovi´ c, Mario Mikoˇ cevi´ c—many bug reports and suggestions.
    • Fran¸ cois Pinard—many thorough bug reports and discussions.
    • Karl Eichwalder—lots of help with internationalization, Makefile layout and many other
    things.
    • Junio Hamano—donated support for Opie and http Digest authentication.
    • Mauro Tortonesi—improved IPv6 support, adding support for dual family systems. Refac-
    tored and enhanced FTP IPv6 code. Maintained GNU Wget from 2004–2007.
    Chapter 9: Appendices 58
    • Christopher G. Lewis—maintenance of the Windows version of GNU WGet.
    • Gisle Vanem—many helpful patches and improvements, especially for Windows and MS-
    DOS support.
    • Ralf Wildenhues—contributed patches to convert Wget to use Automake as part of its build
    process, and various bugfixes.
    • Steven Schubiger—Many helpful patches, bugfixes and improvements. Notably, conversion
    of Wget to use the Gnulib quotes and quoteargs modules, and the addition of password
    prompts at the console, via the Gnulib getpasswd-gnu module.
    • Ted Mielczarek—donated support for CSS.
    • Saint Xavier—Support for IRIs (RFC 3987).
    • People who provided donations for development—including Brian Gough.
    The following people have provided patches, bug/build reports, useful suggestions, beta test-
    ing services, fan mail and all the other things that make maintenance so much fun:
    Tim Adam, Adrian Aichner, Martin Baehr, Dieter Baron, Roger Beeman, Dan Berger, T.
    Bharath, Christian Biere, Paul Bludov, Daniel Bodea, Mark Boyns, John Burden, Julien Buty,
    Wanderlei Cavassin, Gilles Cedoc, Tim Charron, Noel Cragg, Kristijan
    ˇ
    Conkaˇ s, John Daily, An-
    dreas Damm, Ahmon Dancy, Andrew Davison, Bertrand Demiddelaer, Alexander Dergachev,
    Andrew Deryabin, Ulrich Drepper, Marc Duponcheel, Damir Dˇ zeko, Alan Eldridge, Hans-
    Andreas Engel, Aleksandar Erkalovi´ c, Andy Eskilsson, Jo~ ao Ferreira, Christian Fraenkel, David
    Fritz, Mike Frysinger, Charles C. Fu, FUJISHIMA Satsuki, Masashi Fujita, Howard Gayle, Mar-
    cel Gerrits, Lemble Gregory, Hans Grobler, Alain Guibert, Mathieu Guillaume, Aaron Hawley,
    Jochen Hein, Karl Heuer, Madhusudan Hosaagrahara, HIROSE Masaaki, Ulf Harnhammar, Gre-
    gor Hoffleit, Erik Magnus Hulthen, Richard Huveneers, Jonas Jensen, Larry Jones, Simon Josef-
    sson, Mario Juri´ c, Hack Kampbjørn, Const Kaplinsky, Goran Kezunovi´ c, Igor Khristophorov,
    Robert Kleine, KOJIMA Haime, Fila Kolodny, Alexander Kourakos, Martin Kraemer, Sami
    Krank, Jay Krell, (Simos KSenitellis), Christian Lackas, Hrvoje Lacko, Daniel S. Lewart,
    Nicolás Lichtmeier, Dave Love, Alexander V. Lukyanov, Thomas Lußnig, Andre Majorel, Au-
    relien Marchand, Matthew J. Mellon, Jordan Mendelson, Ted Mielczarek, Robert Millan, Lin
    Zhe Min, Jan Minar, Tim Mooney, Keith Moore, Adam D. Moss, Simon Munton, Charlie Ne-
    gyesi, R. K. Owen, Jim Paris, Kenny Parnell, Leonid Petrov, Simone Piunno, Andrew Pollock,
    Steve Pothier, Jan Pˇ rikryl, Marin Purgar, Csaba Ráduly, Keith Refson, Bill Richardson, Tyler
    Riddle, Tobias Ringstrom, Jochen Roderburg, Juan Jos´ e Rodr´ıguez, Maciej W. Rozycki, Ed-
    ward J. Sabol, Heinz Salzmann, Robert Schmidt, Nicolas Schodet, Benno Schulenberg, Andreas
    Schwab, Steven M. Schweda, Chris Seawood, Pranab Shenoy, Dennis Smit, Toomas Soome,
    Tage Stabell-Kulo, Philip Stadermann, Daniel Stenberg, Sven Sternberger, Markus Strasser,
    John Summerfield, Szakacsits Szabolcs, Mike Thomas, Philipp Thomas, Mauro Tortonesi, Dave
    Turner, Gisle Vanem, Rabin Vincent, Russell Vincent,
    ˇ
    Zeljko Vrba, Charles G Waldman, Dou-
    glas E. Wegscheid, Ralf Wildenhues, Joshua David Williams, Benjamin Wolsey, Saint Xavier,
    YAMAZAKI Makoto, Jasmin Zainul, Bojan
    ˇ
    Zdrnja, Kristijan Zimmer, Xin Zou.
    Apologies to all who I accidentally left out, and many thanks to all the subscribers of the
    Wget mailing list.
    Appendix A: Copying this manual 59
    Appendix A Copying this manual
    A.1 GNU Free Documentation License
    Version 1.3, 3 November 2008
    Copyright c ? 2000, 2001, 2002, 2007, 2008, 2015 Free Software
    Foundation, Inc.
    http://fsf.org/
    Everyone is permitted to copy and distribute verbatim copies
    of this license document, but changing it is not allowed.
  • PREAMBLE
    The purpose of this License is to make a manual, textbook, or other functional and useful
    document free in the sense of freedom: to assure everyone the effective freedom to copy
    and redistribute it, with or without modifying it, either commercially or noncommercially.
    Secondarily, this License preserves for the author and publisher a way to get credit for their
    work, while not being considered responsible for modifications made by others.
    This License is a kind of “copyleft”, which means that derivative works of the document
    must themselves be free in the same sense. It complements the GNU General Public License,
    which is a copyleft license designed for free software.
    We have designed this License in order to use it for manuals for free software, because free
    software needs free documentation: a free program should come with manuals providing the
    same freedoms that the software does. But this License is not limited to software manuals;
    it can be used for any textual work, regardless of subject matter or whether it is published
    as a printed book. We recommend this License principally for works whose purpose is
    instruction or reference.
  • APPLICABILITY AND DEFINITIONS
    This License applies to any manual or other work, in any medium, that contains a notice
    placed by the copyright holder saying it can be distributed under the terms of this License.
    Such a notice grants a world-wide, royalty-free license, unlimited in duration, to use that
    work under the conditions stated herein. The “Document”, below, refers to any such manual
    or work. Any member of the public is a licensee, and is addressed as “you”. You accept
    the license if you copy, modify or distribute the work in a way requiring permission under
    copyright law.
    A “Modified Version” of the Document means any work containing the Document or a
    portion of it, either copied verbatim, or with modifications and/or translated into another
    language.
    A “Secondary Section” is a named appendix or a front-matter section of the Document
    that deals exclusively with the relationship of the publishers or authors of the Document
    to the Document’s overall subject (or to related matters) and contains nothing that could
    fall directly within that overall subject. (Thus, if the Document is in part a textbook of
    mathematics, a Secondary Section may not explain any mathematics.) The relationship
    could be a matter of historical connection with the subject or with related matters, or of
    legal, commercial, philosophical, ethical or political position regarding them.
    The “Invariant Sections” are certain Secondary Sections whose titles are designated, as
    being those of Invariant Sections, in the notice that says that the Document is released
    under this License. If a section does not fit the above definition of Secondary then it is not
    allowed to be designated as Invariant. The Document may contain zero Invariant Sections.
    If the Document does not identify any Invariant Sections then there are none.
    Appendix A: Copying this manual 60
    The “Cover Texts” are certain short passages of text that are listed, as Front-Cover Texts or
    Back-Cover Texts, in the notice that says that the Document is released under this License.
    A Front-Cover Text may be at most 5 words, and a Back-Cover Text may be at most 25
    words.
    A “Transparent” copy of the Document means a machine-readable copy, represented in a
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    the document straightforwardly with generic text editors or (for images composed of pixels)
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    suitable for input to text formatters or for automatic translation to a variety of formats
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    whose markup, or absence of markup, has been arranged to thwart or discourage subsequent
    modification by readers is not Transparent. An image format is not Transparent if used for
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    Examples of suitable formats for Transparent copies include plain ASCII without markup,
    Texinfo input format, LaT E X input format, SGML or XML using a publicly available DTD,
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    cation. Examples of transparent image formats include PNG, XCF and JPG. Opaque
    formats include proprietary formats that can be read and edited only by proprietary word
    processors, SGML or XML for which the DTD and/or processing tools are not generally
    available, and the machine-generated HTML, PostScript or PDF produced by some word
    processors for output purposes only.
    The “Title Page” means, for a printed book, the title page itself, plus such following pages
    as are needed to hold, legibly, the material this License requires to appear in the title page.
    For works in formats which do not have any title page as such, “Title Page” means the
    text near the most prominent appearance of the work’s title, preceding the beginning of the
    body of the text.
    The “publisher” means any person or entity that distributes copies of the Document to the
    public.
    A section “Entitled XYZ” means a named subunit of the Document whose title either
    is precisely XYZ or contains XYZ in parentheses following text that translates XYZ in
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    Title” of such a section when you modify the Document means that it remains a section
    “Entitled XYZ” according to this definition.
    The Document may include Warranty Disclaimers next to the notice which states that
    this License applies to the Document. These Warranty Disclaimers are considered to be
    included by reference in this License, but only as regards disclaiming warranties: any other
    implication that these Warranty Disclaimers may have is void and has no effect on the
    meaning of this License.
  • VERBATIM COPYING
    You may copy and distribute the Document in any medium, either commercially or noncom-
    mercially, provided that this License, the copyright notices, and the license notice saying
    this License applies to the Document are reproduced in all copies, and that you add no
    other conditions whatsoever to those of this License. You may not use technical measures
    to obstruct or control the reading or further copying of the copies you make or distribute.
    However, you may accept compensation in exchange for copies. If you distribute a large
    enough number of copies you must also follow the conditions in section 3.
    You may also lend copies, under the same conditions stated above, and you may publicly
    display copies.
    Appendix A: Copying this manual 61
  • COPYING IN QUANTITY
    If you publish printed copies (or copies in media that commonly have printed covers) of the
    Document, numbering more than 100, and the Document’s license notice requires Cover
    Texts, you must enclose the copies in covers that carry, clearly and legibly, all these Cover
    Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on the back cover. Both
    covers must also clearly and legibly identify you as the publisher of these copies. The front
    cover must present the full title with all words of the title equally prominent and visible.
    You may add other material on the covers in addition. Copying with changes limited to
    the covers, as long as they preserve the title of the Document and satisfy these conditions,
    can be treated as verbatim copying in other respects.
    If the required texts for either cover are too voluminous to fit legibly, you should put the
    first ones listed (as many as fit reasonably) on the actual cover, and continue the rest onto
    adjacent pages.
    If you publish or distribute Opaque copies of the Document numbering more than 100, you
    must either include a machine-readable Transparent copy along with each Opaque copy,
    or state in or with each Opaque copy a computer-network location from which the general
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    complete Transparent copy of the Document, free of added material. If you use the latter
    option, you must take reasonably prudent steps, when you begin distribution of Opaque
    copies in quantity, to ensure that this Transparent copy will remain thus accessible at the
    stated location until at least one year after the last time you distribute an Opaque copy
    (directly or through your agents or retailers) of that edition to the public.
    It is requested, but not required, that you contact the authors of the Document well before
    redistributing any large number of copies, to give them a chance to provide you with an
    updated version of the Document.
  • MODIFICATIONS
    You may copy and distribute a Modified Version of the Document under the conditions
    of sections 2 and 3 above, provided that you release the Modified Version under precisely
    this License, with the Modified Version filling the role of the Document, thus licensing
    distribution and modification of the Modified Version to whoever possesses a copy of it. In
    addition, you must do these things in the Modified Version:
    A. Use in the Title Page (and on the covers, if any) a title distinct from that of the
    Document, and from those of previous versions (which should, if there were any, be
    listed in the History section of the Document). You may use the same title as a previous
    version if the original publisher of that version gives permission.
    B. List on the Title Page, as authors, one or more persons or entities responsible for
    authorship of the modifications in the Modified Version, together with at least five of
    the principal authors of the Document (all of its principal authors, if it has fewer than
    five), unless they release you from this requirement.
    C. State on the Title page the name of the publisher of the Modified Version, as the
    publisher.
    D. Preserve all the copyright notices of the Document.
    E. Add an appropriate copyright notice for your modifications adjacent to the other copy-
    right notices.
    F. Include, immediately after the copyright notices, a license notice giving the public
    permission to use the Modified Version under the terms of this License, in the form
    shown in the Addendum below.
    G. Preserve in that license notice the full lists of Invariant Sections and required Cover
    Texts given in the Document’s license notice.
    Appendix A: Copying this manual 62
    H. Include an unaltered copy of this License.
    I. Preserve the section Entitled “History”, Preserve its Title, and add to it an item stating
    at least the title, year, new authors, and publisher of the Modified Version as given
    on the Title Page. If there is no section Entitled “History” in the Document, create
    one stating the title, year, authors, and publisher of the Document as given on its
    Title Page, then add an item describing the Modified Version as stated in the previous
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    J. Preserve the network location, if any, given in the Document for public access to a
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    K. For any section Entitled “Acknowledgements” or “Dedications”, Preserve the Title
    of the section, and preserve in the section all the substance and tone of each of the
    contributor acknowledgements and/or dedications given therein.
    L. Preserve all the Invariant Sections of the Document, unaltered in their text and in their
    titles. Section numbers or the equivalent are not considered part of the section titles.
    M. Delete any section Entitled “Endorsements”. Such a section may not be included in
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    N. Do not retitle any existing section to be Entitled “Endorsements” or to conflict in title
    with any Invariant Section.
    O. Preserve any Warranty Disclaimers.
    If the Modified Version includes new front-matter sections or appendices that qualify as
    Secondary Sections and contain no material copied from the Document, you may at your
    option designate some or all of these sections as invariant. To do this, add their titles to
    the list of Invariant Sections in the Modified Version’s license notice. These titles must be
    distinct from any other section titles.
    You may add a section Entitled “Endorsements”, provided it contains nothing but endorse-
    ments of your Modified Version by various parties—for example, statements of peer review
    or that the text has been approved by an organization as the authoritative definition of a
    standard.
    You may add a passage of up to five words as a Front-Cover Text, and a passage of up
    to 25 words as a Back-Cover Text, to the end of the list of Cover Texts in the Modified
    Version. Only one passage of Front-Cover Text and one of Back-Cover Text may be added
    by (or through arrangements made by) any one entity. If the Document already includes
    a cover text for the same cover, previously added by you or by arrangement made by the
    same entity you are acting on behalf of, you may not add another; but you may replace the
    old one, on explicit permission from the previous publisher that added the old one.
    The author(s) and publisher(s) of the Document do not by this License give permission to
    use their names for publicity for or to assert or imply endorsement of any Modified Version.
  • COMBINING DOCUMENTS
    You may combine the Document with other documents released under this License, under
    the terms defined in section 4 above for modified versions, provided that you include in the
    combination all of the Invariant Sections of all of the original documents, unmodified, and
    list them all as Invariant Sections of your combined work in its license notice, and that you
    preserve all their Warranty Disclaimers.
    The combined work need only contain one copy of this License, and multiple identical
    Invariant Sections may be replaced with a single copy. If there are multiple Invariant
    Appendix A: Copying this manual 63
    Sections with the same name but different contents, make the title of each such section
    unique by adding at the end of it, in parentheses, the name of the original author or
    publisher of that section if known, or else a unique number. Make the same adjustment to
    the section titles in the list of Invariant Sections in the license notice of the combined work.
    In the combination, you must combine any sections Entitled “History” in the various original
    documents, forming one section Entitled “History”; likewise combine any sections Entitled
    “Acknowledgements”, and any sections Entitled “Dedications”. You must delete all sections
    Entitled “Endorsements.”
  • COLLECTIONS OF DOCUMENTS
    You may make a collection consisting of the Document and other documents released under
    this License, and replace the individual copies of this License in the various documents with
    a single copy that is included in the collection, provided that you follow the rules of this
    License for verbatim copying of each of the documents in all other respects.
    You may extract a single document from such a collection, and distribute it individually
    under this License, provided you insert a copy of this License into the extracted document,
    and follow this License in all other respects regarding verbatim copying of that document.
  • AGGREGATION WITH INDEPENDENT WORKS
    A compilation of the Document or its derivatives with other separate and independent
    documents or works, in or on a volume of a storage or distribution medium, is called an
    “aggregate” if the copyright resulting from the compilation is not used to limit the legal
    rights of the compilation’s users beyond what the individual works permit. When the
    Document is included in an aggregate, this License does not apply to the other works in
    the aggregate which are not themselves derivative works of the Document.
    If the Cover Text requirement of section 3 is applicable to these copies of the Document,
    then if the Document is less than one half of the entire aggregate, the Document’s Cover
    Texts may be placed on covers that bracket the Document within the aggregate, or the
    electronic equivalent of covers if the Document is in electronic form. Otherwise they must
    appear on printed covers that bracket the whole aggregate.
  • TRANSLATION
    Translation is considered a kind of modification, so you may distribute translations of the
    Document under the terms of section 4. Replacing Invariant Sections with translations
    requires special permission from their copyright holders, but you may include translations
    of some or all Invariant Sections in addition to the original versions of these Invariant
    Sections. You may include a translation of this License, and all the license notices in
    the Document, and any Warranty Disclaimers, provided that you also include the original
    English version of this License and the original versions of those notices and disclaimers. In
    case of a disagreement between the translation and the original version of this License or a
    notice or disclaimer, the original version will prevail.
    If a section in the Document is Entitled “Acknowledgements”, “Dedications”, or “History”,
    the requirement (section 4) to Preserve its Title (section 1) will typically require changing
    the actual title.
  • TERMINATION
    You may not copy, modify, sublicense, or distribute the Document except as expressly pro-
    vided under this License. Any attempt otherwise to copy, modify, sublicense, or distribute
    it is void, and will automatically terminate your rights under this License.
    However, if you cease all violation of this License, then your license from a particular copy-
    right holder is reinstated (a) provisionally, unless and until the copyright holder explicitly
    and finally terminates your license, and (b) permanently, if the copyright holder fails to
    notify you of the violation by some reasonable means prior to 60 days after the cessation.
    Appendix A: Copying this manual 64
    Moreover, your license from a particular copyright holder is reinstated permanently if the
    copyright holder notifies you of the violation by some reasonable means, this is the first
    time you have received notice of violation of this License (for any work) from that copyright
    holder, and you cure the violation prior to 30 days after your receipt of the notice.
    Termination of your rights under this section does not terminate the licenses of parties
    who have received copies or rights from you under this License. If your rights have been
    terminated and not permanently reinstated, receipt of a copy of some or all of the same
    material does not give you any rights to use it.
  • FUTURE REVISIONS OF THIS LICENSE
    The Free Software Foundation may publish new, revised versions of the GNU Free Doc-
    umentation License from time to time. Such new versions will be similar in spirit to
    the present version, but may differ in detail to address new problems or concerns. See
    http://www.gnu.org/copyleft/.
    Each version of the License is given a distinguishing version number. If the Document
    specifies that a particular numbered version of this License “or any later version” applies
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    version or of any later version that has been published (not as a draft) by the Free Software
    Foundation. If the Document does not specify a version number of this License, you may
    choose any version ever published (not as a draft) by the Free Software Foundation. If the
    Document specifies that a proxy can decide which future versions of this License can be
    used, that proxy’s public statement of acceptance of a version permanently authorizes you
    to choose that version for the Document.
  • RELICENSING
    “Massive Multiauthor Collaboration Site” (or “MMC Site”) means any World Wide Web
    server that publishes copyrightable works and also provides prominent facilities for anybody
    to edit those works. A public wiki that anybody can edit is an example of such a server. A
    “Massive Multiauthor Collaboration” (or “MMC”) contained in the site means any set of
    copyrightable works thus published on the MMC site.
    “CC-BY-SA” means the Creative Commons Attribution-Share Alike 3.0 license published
    by Creative Commons Corporation, a not-for-profit corporation with a principal place of
    business in San Francisco, California, as well as future copyleft versions of that license
    published by that same organization.
    “Incorporate” means to publish or republish a Document, in whole or in part, as part of
    another Document.
    An MMC is “eligible for relicensing” if it is licensed under this License, and if all works that
    were first published under this License somewhere other than this MMC, and subsequently
    incorporated in whole or in part into the MMC, (1) had no cover texts or invariant sections,
    and (2) were thus incorporated prior to November 1, 2008.
    The operator of an MMC Site may republish an MMC contained in the site under CC-BY-
    SA on the same site at any time before August 1, 2009, provided the MMC is eligible for
    relicensing.
    Appendix A: Copying this manual 65
    ADDENDUM: How to use this License for your documents
    To use this License in a document you have written, include a copy of the License in the document
    and put the following copyright and license notices just after the title page:
    Copyright (C) year your name.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.3
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover
    Texts. A copy of the license is included in the section entitled ‘‘GNU
    Free Documentation License’’.
    If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts, replace the
    “with. . .Texts.” line with this:
    with the Invariant Sections being list their titles, with
    the Front-Cover Texts being list, and with the Back-Cover Texts
    being list.
    If you have Invariant Sections without Cover Texts, or some other combination of the three,
    merge those two alternatives to suit the situation.
    If your document contains nontrivial examples of program code, we recommend releasing
    these examples in parallel under your choice of free software license, such as the GNU General
    Public License, to permit their use in free software.
    Concept Index 66
    Concept Index
    (Index is nonexistent)
    ii
    Table of Contents
    1 Overview ....................................................... 1
    2 Invoking........................................................ 2
    2.1 URL Format ...................................................................... 2
    2.2 Option Syntax..................................................................... 3
    2.3 Basic Startup Options............................................................. 3
    2.4 Logging and Input File Options.................................................... 4
    2.5 Download Options................................................................. 5
    2.6 Directory Options................................................................ 13
    2.7 HTTP Options................................................................... 14
    2.8 HTTPS (SSL/TLS) Options...................................................... 20
    2.9 FTP Options..................................................................... 23
    2.10 FTPS Options .................................................................. 25
    2.11 Recursive Retrieval Options ..................................................... 25
    2.12 Recursive Accept/Reject Options................................................ 28
    2.13 Exit Status ..................................................................... 30
    3 Recursive Download ......................................... 31
    4 Following Links............................................... 32
    4.1 Spanning Hosts .................................................................. 32
    4.2 Types of Files.................................................................... 32
    4.3 Directory-Based Limits........................................................... 34
    4.4 Relative Links.................................................................... 35
    4.5 Following FTP Links............................................................. 35
    5 Time-Stamping............................................... 36
    5.1 Time-Stamping Usage............................................................ 36
    5.2 HTTP Time-Stamping Internals.................................................. 37
    5.3 FTP Time-Stamping Internals.................................................... 37
    6 Startup File................................................... 38
    6.1 Wgetrc Location ................................................................. 38
    6.2 Wgetrc Syntax ................................................................... 38
    6.3 Wgetrc Commands............................................................... 38
    6.4 Sample Wgetrc................................................................... 45
    7 Examples...................................................... 49
    7.1 Simple Usage..................................................................... 49
    7.2 Advanced Usage.................................................................. 49
    7.3 Very Advanced Usage ............................................................ 50
    iii
    8 Various........................................................ 52
    8.1 Proxies........................................................................... 52
    8.2 Distribution...................................................................... 53
    8.3 Web Site......................................................................... 53
    8.4 Mailing Lists..................................................................... 53
    Primary List ....................................................................... 53
    Bug Notices List ................................................................... 53
    Obsolete Lists...................................................................... 53
    8.5 Internet Relay Chat .............................................................. 53
    8.6 Reporting Bugs .................................................................. 53
    8.7 Portability ....................................................................... 54
    8.8 Signals........................................................................... 55
    9 Appendices ................................................... 56
    9.1 Robot Exclusion.................................................................. 56
    9.2 Security Considerations........................................................... 57
    9.3 Contributors ..................................................................... 57
    Appendix A Copying this manual ............................ 59
    A.1 GNU Free Documentation License ............................................... 59
    Concept Index.................................................... 66
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