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| author | Kirill Volinsky <mataes2007@gmail.com> | 2013-11-10 18:02:01 +0000 | 
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| committer | Kirill Volinsky <mataes2007@gmail.com> | 2013-11-10 18:02:01 +0000 | 
| commit | ac48668a549fe76648e0ac3f93c9943383e043f5 (patch) | |
| tree | bcfcf258bd003db20b1ee41fbbff173c8f340031 /plugins/FTPFileYM/curl-7.29.0/docs/FAQ | |
| parent | 64e1340acd813704c9e9009b0a4e6fc9a3fb5adf (diff) | |
curl folder renamed
git-svn-id: http://svn.miranda-ng.org/main/trunk@6858 1316c22d-e87f-b044-9b9b-93d7a3e3ba9c
Diffstat (limited to 'plugins/FTPFileYM/curl-7.29.0/docs/FAQ')
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diff --git a/plugins/FTPFileYM/curl-7.29.0/docs/FAQ b/plugins/FTPFileYM/curl-7.29.0/docs/FAQ deleted file mode 100644 index 48075cea6d..0000000000 --- a/plugins/FTPFileYM/curl-7.29.0/docs/FAQ +++ /dev/null @@ -1,1465 +0,0 @@ -                                  _   _ ____  _ -                              ___| | | |  _ \| | -                             / __| | | | |_) | | -                            | (__| |_| |  _ <| |___ -                             \___|\___/|_| \_\_____| - -FAQ - - 1. 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? - - 2. 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) ? - - 3. 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 - - 4. 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? - - 5. 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? - - 6. 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? - - 7. 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, SMTP, SMTPS, TELNET and TFTP. - -    libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading, -    kerberos, 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, HPUX, -    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 and cURL with an initial k sound: [kurl]. - -  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. - -  * 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 -  (lib)curl on full or even part time. We do this voluntarily on our 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 and sourceforge.net hosts project services we take advantage from, -  like the bug tracker. 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 -  first-hand 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 -  http://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: -  http://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. 300 million! - -  See http://daniel.haxx.se/blog/2012/05/16/300m-users/ - -  1.11 Why don't you update ca-bundle.crt - -  The ca-bundle.crt file that used to be bundled with curl was very outdated -  (it being last modified year 2000 should tell) and must be replaced with a -  much more modern and up-to-date version by anyone who wants to verify peers -  anyway. It is no longer provided, the last curl release that shipped it 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: http://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. - -  ASF gives a good explanation at http://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, 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. - - -2. 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), -  schannel (native Windows) or qssl (native IBM i). They all have their pros -  and cons, and we try to maintain a comparison of them here: -  http://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 uses OpenSSL to do the SSL stuff. The LIBEAY32.DLL is what curl needs -  on a windows machine to do https://. 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. - - -3. 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 assumes one of the formats. If the form you're trying to -  "fake" sets the type to '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: -  http://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 -    (http://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 (ie 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 change curl's behavior. It only modifies the actual -  string sent in the request. - -  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. - - -4. 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 %-symbol specially and you -  need to use TWO %-symbols for each single one you want to use in the URL. - -  Also note that if you want the literal %-symbol 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 %-symbol 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: - -       <H1>Moved Permanently</H1> The document has moved <A -       HREF="http://same_url_now_with_a_trailing_slash/">here</A>. - -    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: http://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 directs 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: -  http://support.microsoft.com/?scid=kb%3Ben-us%3B175523&x=6&y=7 - -  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 (http://www.faqs.org/rfcs/rfc1738.html), -  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 the 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. - -  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 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. - - -5. 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. - -  If you use a OpenSSL-powered libcurl in a multi-threaded environment, you -  need to provide one or two locking functions: - -    http://www.openssl.org/docs/crypto/threads.html - -  If you use a GnuTLS-powered libcurl in a multi-threaded environment, you -  need to provide locking function(s) for libgcrypt (which is used by GnuTLS -  for the crypto functions). - -    http://www.gnu.org/software/gnutls/manual/html_node/Multi_002dthreaded-applications.html - -  No special locking is needed with a NSS-powered libcurl. NSS is thread-safe. - -  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 __imp__curl_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 than so. Besides, faking IP address -  would imply sending IP packages with a made-up source address, and then you -  normally get a problem with intercepting the packages 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. - -  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<YourClass*>(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 http://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! - - -6. 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: http://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. - - -7. 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 is a module that comes with the regular PHP package. It depends and -  uses libcurl, so you need to have libcurl installed properly first before -  PHP/CURL can be used. 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 to re-use the same connection if it can.  | 
