5 \___|\___/|_| \_\_____|
13 1.4 When will you make curl do XXXX ?
15 1.6 What do you get for making curl?
16 1.7 What about CURL from curl.com?
17 1.8 I have a problem who do I mail?
18 1.9 Where do I buy commercial support for curl?
19 1.10 How many are using curl?
20 1.11 Why don't you update ca-bundle.crt
21 1.12 I have a problem who can I chat with?
22 1.13 curl's ECCN number?
23 1.14 How do I submit my patch?
25 2. Install Related Problems
26 2.1 configure doesn't find OpenSSL even when it is installed
27 2.1.1 native linker doesn't find OpenSSL
28 2.1.2 only the libssl lib is missing
29 2.2 Does curl work/build with other SSL libraries?
30 2.3 Where can I find a copy of LIBEAY32.DLL?
31 2.4 Does curl support SOCKS (RFC 1928) ?
34 3.1 curl: (1) SSL is disabled, https: not supported
35 3.2 How do I tell curl to resume a transfer?
36 3.3 Why doesn't my posting using -F work?
37 3.4 How do I tell curl to run custom FTP commands?
38 3.5 How can I disable the Accept: */* header?
39 3.6 Does curl support ASP, XML, XHTML or HTML version Y?
40 3.7 Can I use curl to delete/rename a file through FTP?
41 3.8 How do I tell curl to follow HTTP redirects?
42 3.9 How do I use curl in my favorite programming language?
43 3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
44 3.11 How do I POST with a different Content-Type?
45 3.12 Why do FTP specific features over HTTP proxy fail?
46 3.13 Why does my single/double quotes fail?
47 3.14 Does curl support Javascript or PAC (automated proxy config)?
48 3.15 Can I do recursive fetches with curl?
49 3.16 What certificates do I need when I use SSL?
50 3.17 How do I list the root dir of an FTP server?
51 3.18 Can I use curl to send a POST/PUT and not wait for a response?
52 3.19 How do I get HTTP from a host using a specific IP address?
53 3.20 How to SFTP from my user's home directory?
54 3.21 Protocol xxx not supported or disabled in libcurl
55 3.22 curl -X gives me HTTP problems
58 4.1 Problems connecting to SSL servers.
59 4.2 Why do I get problems when I use & or % in the URL?
60 4.3 How can I use {, }, [ or ] to specify multiple URLs?
61 4.4 Why do I get downloaded data even though the web page doesn't exist?
62 4.5 Why do I get return code XXX from a HTTP server?
63 4.5.1 "400 Bad Request"
64 4.5.2 "401 Unauthorized"
67 4.5.5 "405 Method Not Allowed"
68 4.5.6 "301 Moved Permanently"
69 4.6 Can you tell me what error code 142 means?
70 4.7 How do I keep user names and passwords secret in Curl command lines?
72 4.9 Curl can't authenticate to the server that requires NTLM?
73 4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!
74 4.11 Why does my HTTP range requests return the full document?
75 4.12 Why do I get "certificate verify failed" ?
76 4.13 Why is curl -R on Windows one hour off?
77 4.14 Redirects work in browser but not with curl!
78 4.15 FTPS doesn't work
79 4.16 My HTTP POST or PUT requests are slow!
80 4.17 Non-functional connect timeouts on Windows
81 4.18 file:// URLs containing drive letters (Windows, NetWare)
82 4.19 Why doesn't cURL return an error when the network cable is unplugged?
85 5.1 Is libcurl thread-safe?
86 5.2 How can I receive all data into a large memory chunk?
87 5.3 How do I fetch multiple files with libcurl?
88 5.4 Does libcurl do Winsock initing on win32 systems?
89 5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?
90 5.6 What about Keep-Alive or persistent connections?
91 5.7 Link errors when building libcurl on Windows!
92 5.8 libcurl.so.X: open failed: No such file or directory
93 5.9 How does libcurl resolve host names?
94 5.10 How do I prevent libcurl from writing the response to stdout?
95 5.11 How do I make libcurl not receive the whole HTTP response?
96 5.12 Can I make libcurl fake or hide my real IP address?
97 5.13 How do I stop an ongoing transfer?
98 5.14 Using C++ non-static functions for callbacks?
99 5.15 How do I get an FTP directory listing?
100 5.16 I want a different time-out!
101 5.17 Can I write a server with libcurl?
104 6.1 I have a GPL program, can I use the libcurl library?
105 6.2 I have a closed-source program, can I use the libcurl library?
106 6.3 I have a BSD licensed program, can I use the libcurl library?
107 6.4 I have a program that uses LGPL libraries, can I use libcurl?
108 6.5 Can I modify curl/libcurl for my program and keep the changes secret?
109 6.6 Can you please change the curl/libcurl license to XXXX?
110 6.7 What are my obligations when using libcurl in my commercial apps?
113 7.1 What is PHP/CURL?
114 7.2 Who wrote PHP/CURL?
115 7.3 Can I perform multiple requests using the same handle?
117 ==============================================================================
123 cURL is the name of the project. The name is a play on 'Client for URLs',
124 originally with URL spelled in uppercase to make it obvious it deals with
125 URLs. The fact it can also be pronounced 'see URL' also helped, it works as
126 an abbreviation for "Client URL Request Library" or why not the recursive
127 version: "Curl URL Request Library".
129 The cURL project produces two products:
133 A free and easy-to-use client-side URL transfer library, supporting DICT,
134 FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3,
135 POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP.
137 libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading,
138 kerberos, HTTP form based upload, proxies, cookies, user+password
139 authentication, file transfer resume, http proxy tunneling and more!
141 libcurl is highly portable, it builds and works identically on numerous
142 platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HPUX,
143 IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, BeOS, Mac
144 OS X, Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS, Symbian, OSF,
145 Android, Minix, IBM TPF and more...
147 libcurl is free, thread-safe, IPv6 compatible, feature rich, well
152 A command line tool for getting or sending files using URL syntax.
154 Since curl uses libcurl, curl supports the same wide range of common
155 Internet protocols that libcurl does.
157 We pronounce curl and cURL with an initial k sound: [kurl].
159 There are numerous sub-projects and related projects that also use the word
160 curl in the project names in various combinations, but you should take
161 notice that this FAQ is directed at the command-line tool named curl (and
162 libcurl the library), and may therefore not be valid for other curl-related
163 projects. (There is however a small section for the PHP/CURL in this FAQ.)
167 libcurl is a reliable and portable library which provides you with an easy
168 interface to a range of common Internet protocols.
170 You can use libcurl for free in your application, be it open source,
171 commercial or closed-source.
173 libcurl is most probably the most portable, most powerful and most often
174 used C-based multi-platform file transfer library on this planet - be it
175 open source or commercial.
177 1.3 What is curl not?
179 Curl is not a wget clone. That is a common misconception. Never, during
180 curl's development, have we intended curl to replace wget or compete on its
181 market. Curl is targeted at single-shot file transfers.
183 Curl is not a web site mirroring program. If you want to use curl to mirror
184 something: fine, go ahead and write a script that wraps around curl to make
185 it reality (like curlmirror.pl does).
187 Curl is not an FTP site mirroring program. Sure, get and send FTP with curl
188 but if you want systematic and sequential behavior you should write a
189 script (or write a new program that interfaces libcurl) and do it.
191 Curl is not a PHP tool, even though it works perfectly well when used from
192 or with PHP (when using the PHP/CURL module).
194 Curl is not a program for a single operating system. Curl exists, compiles,
195 builds and runs under a wide range of operating systems, including all
196 modern Unixes (and a bunch of older ones too), Windows, Amiga, BeOS, OS/2,
199 1.4 When will you make curl do XXXX ?
201 We love suggestions of what to change in order to make curl and libcurl
202 better. We do however believe in a few rules when it comes to the future of
205 Curl -- the command line tool -- is to remain a non-graphical command line
206 tool. If you want GUIs or fancy scripting capabilities, you should look for
207 another tool that uses libcurl.
209 We do not add things to curl that other small and available tools already do
210 very fine at the side. Curl's output is fine to pipe into another program or
211 redirect to another file for the next program to interpret.
213 We focus on protocol related issues and improvements. If you wanna do more
214 magic with the supported protocols than curl currently does, chances are big
215 we will agree. If you wanna add more protocols, we may very well agree.
217 If you want someone else to make all the work while you wait for us to
218 implement it for you, that is not a very friendly attitude. We spend a
219 considerable time already on maintaining and developing curl. In order to
220 get more out of us, you should consider trading in some of your time and
223 If you write the code, chances are bigger that it will get into curl faster.
227 curl and libcurl are not made by any single individual. Daniel Stenberg is
228 project leader and main developer, but other persons' submissions are
229 important and crucial. Anyone can contribute and post their changes and
230 improvements and have them inserted in the main sources (of course on the
231 condition that developers agree on that the fixes are good).
233 The full list of all contributors is found in the docs/THANKS file.
235 curl is developed by a community, with Daniel at the wheel.
237 1.6 What do you get for making curl?
239 Project cURL is entirely free and open. No person gets paid for developing
240 (lib)curl on full or even part time. We do this voluntarily on our spare
241 time. Occasionally companies pay individual developers to work on curl, but
242 that's up to each company and developer. It is not controlled by nor
243 supervised in any way by the project.
245 We still get help from companies. Haxx provides web site, bandwidth, mailing
246 lists etc, sourceforge.net hosts project services we take advantage from,
247 like the bug tracker and github hosts the primary git repository. Also
248 again, some companies have sponsored certain parts of the development in the
249 past and I hope some will continue to do so in the future.
251 If you want to support our project, consider a donation or a banner-program
252 or even better: by helping us coding, documenting, testing etc.
254 1.7 What about CURL from curl.com?
256 During the summer 2001, curl.com was busy advertising their client-side
257 programming language for the web, named CURL.
259 We are in no way associated with curl.com or their CURL programming
262 Our project name curl has been in effective use since 1998. We were not the
263 first computer related project to use the name "curl" and do not claim any
266 We recognize that we will be living in parallel with curl.com and wish them
269 1.8 I have a problem who do I mail?
271 Please do not mail any single individual unless you really need to. Keep
272 curl-related questions on a suitable mailing list. All available mailing
273 lists are listed in the MANUAL document and online at
274 http://curl.haxx.se/mail/
276 Keeping curl-related questions and discussions on mailing lists allows
277 others to join in and help, to share their ideas, contribute their
278 suggestions and spread their wisdom. Keeping discussions on public mailing
279 lists also allows for others to learn from this (both current and future
280 users thanks to the web based archives of the mailing lists), thus saving us
281 from having to repeat ourselves even more. Thanks for respecting this.
283 If you have found or simply suspect a security problem in curl or libcurl,
284 mail curl-security at haxx.se (closed list of receivers, mails are not
285 disclosed) and tell. Then we can produce a fix in a timely manner before the
286 flaw is announced to the world, thus lessen the impact the problem will have
289 1.9 Where do I buy commercial support for curl?
291 curl is fully open source. It means you can hire any skilled engineer to fix
292 your curl-related problems.
294 We list available alternatives on the curl web site:
295 http://curl.haxx.se/support.html
297 1.10 How many are using curl?
299 It is impossible to tell.
301 We don't know how many users that knowingly have installed and use curl.
303 We don't know how many users that use curl without knowing that they are in
306 We don't know how many users that downloaded or installed curl and then
309 In May 2012 Daniel did a counting game and came up with a number that may
310 be completely wrong or somewhat accurate. Over 500 million!
312 See http://daniel.haxx.se/blog/2012/05/16/300m-users/
314 1.11 Why don't you update ca-bundle.crt
316 The ca cert bundle that used to shipped with curl was very outdated and must
317 be replaced with an up-to-date version by anyone who wants to verify
318 peers. It is no longer provided by curl. The last curl release ever that
319 shipped a ca cert bundle was curl 7.18.0.
321 In the cURL project we've decided not to attempt to keep this file updated
322 (or even present anymore) since deciding what to add to a ca cert bundle is
323 an undertaking we've not been ready to accept, and the one we can get from
324 Mozilla is perfectly fine so there's no need to duplicate that work.
326 Today, with many services performed over HTTPS, every operating system
327 should come with a default ca cert bundle that can be deemed somewhat
328 trustworthy and that collection (if reasonably updated) should be deemed to
329 be a lot better than a private curl version.
331 If you want the most recent collection of ca certs that Mozilla Firefox
332 uses, we recommend that you extract the collection yourself from Mozilla
333 Firefox (by running 'make ca-bundle), or by using our online service setup
334 for this purpose: http://curl.haxx.se/docs/caextract.html
336 1.12 I have a problem who can I chat with?
338 There's a bunch of friendly people hanging out in the #curl channel on the
339 IRC network irc.freenode.net. If you're polite and nice, chances are big
340 that you can get -- or provide -- help instantly.
342 1.13 curl's ECCN number?
344 The US government restricts exports of software that contains or uses
345 cryptography. When doing so, the Export Control Classification Number (ECCN)
346 is used to identify the level of export control etc.
348 ASF gives a good explanation at http://www.apache.org/dev/crypto.html
350 We believe curl's number might be ECCN 5D002, another possibility is
351 5D992. It seems necessary to write them, asking to confirm.
353 Comprehensible explanations of the meaning of such numbers and how to
354 obtain them (resp.) are here
356 http://www.bis.doc.gov/licensing/exportingbasics.htm
357 http://www.bis.doc.gov/licensing/do_i_needaneccn.html
359 An incomprehensible description of the two numbers above is here
360 http://www.access.gpo.gov/bis/ear/pdf/ccl5-pt2.pdf
362 1.14 How do I submit my patch?
364 When you have made a patch or a change of whatever sort, and want to submit
365 that to the project, there are a few different ways we prefer:
367 o send a patch to the curl-library mailing list. We're many subscribers
368 there and there are lots of people who can review patches, comment on them
369 and "receive" them properly.
371 o if your patch changes or fixes a bug, you can also opt to submit a bug
372 report in the bug tracker and attach your patch there. There are less
373 people involved there.
375 Lots of more details are found in the CONTRIBUTE and INTERNALS docs.
378 2. Install Related Problems
380 2.1 configure doesn't find OpenSSL even when it is installed
382 This may be because of several reasons.
384 2.1.1 native linker doesn't find openssl
387 Solaris (native cc compiler)
388 HPUX (native cc compiler)
389 SGI IRIX (native cc compiler)
390 SCO UNIX (native cc compiler)
392 When configuring curl, I specify --with-ssl. OpenSSL is installed in
393 /usr/local/ssl Configure reports SSL in /usr/local/ssl, but fails to find
394 CRYPTO_lock in -lcrypto
396 Cause: The cc for this test places the -L/usr/local/ssl/lib AFTER
397 -lcrypto, so ld can't find the library. This is due to a bug in the GNU
400 Workaround: Specifying "LDFLAGS=-L/usr/local/ssl/lib" in front of
401 ./configure places the -L/usr/local/ssl/lib early enough in the command
402 line to make things work
404 2.1.2 only the libssl lib is missing
406 If all include files and the libcrypto lib is present, with only the
407 libssl being missing according to configure, this is mostly likely because
408 a few functions are left out from the libssl.
410 If the function names missing include RSA or RSAREF you can be certain
411 that this is because libssl requires the RSA and RSAREF libs to build.
413 See the INSTALL file section that explains how to add those libs to
414 configure. Make sure that you remove the config.cache file before you
415 rerun configure with the new flags.
417 2.2 Does curl work/build with other SSL libraries?
419 Curl has been written to use a generic SSL function layer internally, and
420 that SSL functionality can then be provided by one out of many different SSL
423 curl can be built to use one of the following SSL alternatives: OpenSSL,
424 GnuTLS, yassl, NSS, PolarSSL, axTLS, Secure Transport (native iOS/OS X),
425 WinSSL (native Windows) or qssl (native IBM i). They all have their pros
426 and cons, and we try to maintain a comparison of them here:
427 http://curl.haxx.se/docs/ssl-compared.html
429 2.3 Where can I find a copy of LIBEAY32.DLL?
431 That is an OpenSSL binary built for Windows.
433 Curl can be built with OpenSSL to do the SSL stuff. The LIBEAY32.DLL is then
434 what curl needs on a windows machine to do https:// etc. Check out the curl
435 web site to find accurate and up-to-date pointers to recent OpenSSL DLLs and
436 other binary packages.
438 2.4 Does curl support SOCKS (RFC 1928) ?
440 Yes, SOCKS 4 and 5 are supported.
445 3.1 curl: (1) SSL is disabled, https: not supported
447 If you get this output when trying to get anything from a https:// server,
448 it means that the instance of curl/libcurl that you're using was built
449 without support for this protocol.
451 This could've happened if the configure script that was run at build time
452 couldn't find all libs and include files curl requires for SSL to work. If
453 the configure script fails to find them, curl is simply built without SSL
456 To get the https:// support into a curl that was previously built but that
457 reports that https:// is not supported, you should dig through the document
458 and logs and check out why the configure script doesn't find the SSL libs
459 and/or include files.
461 Also, check out the other paragraph in this FAQ labelled "configure doesn't
462 find OpenSSL even when it is installed".
464 3.2 How do I tell curl to resume a transfer?
466 Curl supports resumed transfers both ways on both FTP and HTTP.
469 3.3 Why doesn't my posting using -F work?
471 You can't simply use -F or -d at your choice. The web server that will
472 receive your post expects one of the formats. If the form you're trying to
473 submit uses the type 'multipart/form-data', then and only then you must use
474 the -F type. In all the most common cases, you should use -d which then
475 causes a posting with the type 'application/x-www-form-urlencoded'.
477 This is described in some detail in the MANUAL and TheArtOfHttpScripting
478 documents, and if you don't understand it the first time, read it again
479 before you post questions about this to the mailing list. Also, try reading
480 through the mailing list archives for old postings and questions regarding
483 3.4 How do I tell curl to run custom FTP commands?
485 You can tell curl to perform optional commands both before and/or after a
486 file transfer. Study the -Q/--quote option.
488 Since curl is used for file transfers, you don't normally use curl to
489 perform FTP commands without transferring anything. Therefore you must
490 always specify a URL to transfer to/from even when doing custom FTP
491 commands, or use -I which implies the "no body" option sent to libcurl.
493 3.5 How can I disable the Accept: */* header?
495 You can change all internally generated headers by adding a replacement with
496 the -H/--header option. By adding a header with empty contents you safely
497 disable that one. Use -H "Accept:" to disable that specific header.
499 3.6 Does curl support ASP, XML, XHTML or HTML version Y?
501 To curl, all contents are alike. It doesn't matter how the page was
502 generated. It may be ASP, PHP, Perl, shell-script, SSI or plain HTML
503 files. There's no difference to curl and it doesn't even know what kind of
504 language that generated the page.
506 See also item 3.14 regarding javascript.
508 3.7 Can I use curl to delete/rename a file through FTP?
510 Yes. You specify custom FTP commands with -Q/--quote.
512 One example would be to delete a file after you have downloaded it:
514 curl -O ftp://download.com/coolfile -Q '-DELE coolfile'
516 or rename a file after upload:
518 curl -T infile ftp://upload.com/dir/ -Q "-RNFR infile" -Q "-RNTO newname"
520 3.8 How do I tell curl to follow HTTP redirects?
522 Curl does not follow so-called redirects by default. The Location: header
523 that informs the client about this is only interpreted if you're using the
524 -L/--location option. As in:
526 curl -L http://redirector.com
528 Not all redirects are HTTP ones, see 4.14
530 3.9 How do I use curl in my favorite programming language?
532 There exist many language interfaces/bindings for curl that integrates it
533 better with various languages. If you are fluid in a script language, you
534 may very well opt to use such an interface instead of using the command line
537 Find out more about which languages that support curl directly, and how to
538 install and use them, in the libcurl section of the curl web site:
539 http://curl.haxx.se/libcurl/
541 All the various bindings to libcurl are made by other projects and people,
542 outside of the cURL project. The cURL project itself only produces libcurl
543 with its plain C API. If you don't find anywhere else to ask you can ask
544 about bindings on the curl-library list too, but be prepared that people on
545 that list may not know anything about bindings.
547 In October 2009, there were interfaces available for the following
548 languages: Ada95, Basic, C, C++, Ch, Cocoa, D, Dylan, Eiffel, Euphoria,
549 Ferite, Gambas, glib/GTK+, Haskell, ILE/RPG, Java, Lisp, Lua, Mono, .NET,
550 Object-Pascal, O'Caml, Pascal, Perl, PHP, PostgreSQL, Python, R, Rexx, Ruby,
551 Scheme, S-Lang, Smalltalk, SP-Forth, SPL, Tcl, Visual Basic, Visual FoxPro,
552 Q, wxwidgets and XBLite. By the time you read this, additional ones may have
555 3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
557 Curl adheres to the HTTP spec, which basically means you can play with *any*
558 protocol that is built on top of HTTP. Protocols such as SOAP, WEBDAV and
559 XML-RPC are all such ones. You can use -X to set custom requests and -H to
560 set custom headers (or replace internally generated ones).
562 Using libcurl is of course just as fine and you'd just use the proper
563 library options to do the same.
565 3.11 How do I POST with a different Content-Type?
567 You can always replace the internally generated headers with -H/--header.
568 To make a simple HTTP POST with text/xml as content-type, do something like:
570 curl -d "datatopost" -H "Content-Type: text/xml" [URL]
572 3.12 Why do FTP specific features over HTTP proxy fail?
574 Because when you use a HTTP proxy, the protocol spoken on the network will
575 be HTTP, even if you specify a FTP URL. This effectively means that you
576 normally can't use FTP specific features such as FTP upload and FTP quote
579 There is one exception to this rule, and that is if you can "tunnel through"
580 the given HTTP proxy. Proxy tunneling is enabled with a special option (-p)
581 and is generally not available as proxy admins usually disable tunneling to
582 other ports than 443 (which is used for HTTPS access through proxies).
584 3.13 Why does my single/double quotes fail?
586 To specify a command line option that includes spaces, you might need to
587 put the entire option within quotes. Like in:
589 curl -d " with spaces " url.com
593 curl -d ' with spaces ' url.com
595 Exactly what kind of quotes and how to do this is entirely up to the shell
596 or command line interpreter that you are using. For most unix shells, you
597 can more or less pick either single (') or double (") quotes. For
598 Windows/DOS prompts I believe you're forced to use double (") quotes.
600 Please study the documentation for your particular environment. Examples in
601 the curl docs will use a mix of both these ones as shown above. You must
602 adjust them to work in your environment.
604 Remember that curl works and runs on more operating systems than most single
605 individuals have ever tried.
607 3.14 Does curl support Javascript or PAC (automated proxy config)?
609 Many web pages do magic stuff using embedded Javascript. Curl and libcurl
610 have no built-in support for that, so it will be treated just like any other
613 .pac files are a netscape invention and are sometimes used by organizations
614 to allow them to differentiate which proxies to use. The .pac contents is
615 just a Javascript program that gets invoked by the browser and that returns
616 the name of the proxy to connect to. Since curl doesn't support Javascript,
617 it can't support .pac proxy configuration either.
619 Some workarounds usually suggested to overcome this Javascript dependency:
621 Depending on the Javascript complexity, write up a script that translates it
622 to another language and execute that.
624 Read the Javascript code and rewrite the same logic in another language.
626 Implement a Javascript interpreter, people have successfully used the
627 Mozilla Javascript engine in the past.
629 Ask your admins to stop this, for a static proxy setup or similar.
631 3.15 Can I do recursive fetches with curl?
633 No. curl itself has no code that performs recursive operations, such as
634 those performed by wget and similar tools.
636 There exist wrapper scripts with that functionality (for example the
637 curlmirror perl script), and you can write programs based on libcurl to do
638 it, but the command line tool curl itself cannot.
640 3.16 What certificates do I need when I use SSL?
642 There are three different kinds of "certificates" to keep track of when we
643 talk about using SSL-based protocols (HTTPS or FTPS) using curl or libcurl.
647 The server you communicate may require that you can provide this in order to
648 prove that you actually are who you claim to be. If the server doesn't
649 require this, you don't need a client certificate.
651 A client certificate is always used together with a private key, and the
652 private key has a pass phrase that protects it.
656 The server you communicate with has a server certificate. You can and should
657 verify this certificate to make sure that you are truly talking to the real
658 server and not a server impersonating it.
660 CERTIFICATE AUTHORITY CERTIFICATE ("CA cert")
662 You often have several CA certs in a CA cert bundle that can be used to
663 verify a server certificate that was signed by one of the authorities in the
664 bundle. curl does not come with a CA cert bundle but most curl installs
665 provide one. You can also override the default.
667 The server certificate verification process is made by using a Certificate
668 Authority certificate ("CA cert") that was used to sign the server
669 certificate. Server certificate verification is enabled by default in curl
670 and libcurl and is often the reason for problems as explained in FAQ entry
671 4.12 and the SSLCERTS document
672 (http://curl.haxx.se/docs/sslcerts.html). Server certificates that are
673 "self-signed" or otherwise signed by a CA that you do not have a CA cert
674 for, cannot be verified. If the verification during a connect fails, you are
675 refused access. You then need to explicitly disable the verification to
676 connect to the server.
678 3.17 How do I list the root dir of an FTP server?
680 There are two ways. The way defined in the RFC is to use an encoded slash
681 in the first path part. List the "/tmp" dir like this:
683 curl ftp://ftp.sunet.se/%2ftmp/
685 or the not-quite-kosher-but-more-readable way, by simply starting the path
686 section of the URL with a slash:
688 curl ftp://ftp.sunet.se//tmp/
690 3.18 Can I use curl to send a POST/PUT and not wait for a response?
694 But you could easily write your own program using libcurl to do such stunts.
696 3.19 How do I get HTTP from a host using a specific IP address?
698 For example, you may be trying out a web site installation that isn't yet in
699 the DNS. Or you have a site using multiple IP addresses for a given host
700 name and you want to address a specific one out of the set.
702 Set a custom Host: header that identifies the server name you want to reach
703 but use the target IP address in the URL:
705 curl --header "Host: www.example.com" http://127.0.0.1/
707 You can also opt to add faked host name entries to curl with the --resolve
708 option. That has the added benefit that things like redirects will also work
709 properly. The above operation would instead be done as:
711 curl --resolve www.example.com:80:127.0.0.1 http://www.example.com/
713 3.20 How to SFTP from my user's home directory?
715 Contrary to how FTP works, SFTP and SCP URLs specify the exact directory to
716 work with. It means that if you don't specify that you want the user's home
717 directory, you get the actual root directory.
719 To specify a file in your user's home directory, you need to use the correct
720 URL syntax which for sftp might look similar to:
722 curl -O -u user:password sftp://example.com/~/file.txt
724 and for SCP it is just a different protocol prefix:
726 curl -O -u user:password scp://example.com/~/file.txt
728 3.21 Protocol xxx not supported or disabled in libcurl
730 When passing on a URL to curl to use, it may respond that the particular
731 protocol is not supported or disabled. The particular way this error message
732 is phrased is because curl doesn't make a distinction internally of whether
733 a particular protocol is not supported (i.e. never got any code added that
734 knows how to speak that protocol) or if it was explicitly disabled. curl can
735 be built to only support a given set of protocols, and the rest would then
736 be disabled or not supported.
738 Note that this error will also occur if you pass a wrongly spelled protocol
739 part as in "htpt://example.com" or as in the less evident case if you prefix
740 the protocol part with a space as in " http://example.com/".
742 3.22 curl -X gives me HTTP problems
744 In normal circumstances, -X should hardly ever be used.
746 By default you use curl without explicitly saying which request method to
747 use when the URL identifies a HTTP transfer. If you just pass in a URL like
748 "curl http://example.com" it will use GET. If you use -d or -F curl will use
749 POST, -I will cause a HEAD and -T will make it a PUT.
751 If for whatever reason you're not happy with these default choices that curl
752 does for you, you can override those request methods by specifying -X
753 [WHATEVER]. This way you can for example send a DELETE by doing "curl -X
756 It is thus pointless to do "curl -XGET [URL]" as GET would be used
757 anyway. In the same vein it is pointless to do "curl -X POST -d data
758 [URL]"... But you can make a fun and somewhat rare request that sends a
759 request-body in a GET request with something like "curl -X GET -d data
762 Note that -X doesn't change curl's behavior. It only modifies the actual
763 string sent in the request.
765 Accordingly, by using -XPOST on a command line that for example would follow
766 a 303 redirect, you will effectively prevent curl from behaving
772 4.1 Problems connecting to SSL servers.
774 It took a very long time before we could sort out why curl had problems to
775 connect to certain SSL servers when using SSLeay or OpenSSL v0.9+. The
776 error sometimes showed up similar to:
778 16570:error:1407D071:SSL routines:SSL2_READ:bad mac decode:s2_pkt.c:233:
780 It turned out to be because many older SSL servers don't deal with SSLv3
781 requests properly. To correct this problem, tell curl to select SSLv2 from
782 the command line (-2/--sslv2).
784 There have also been examples where the remote server didn't like the SSLv2
785 request and instead you had to force curl to use SSLv3 with -3/--sslv3.
787 4.2 Why do I get problems when I use & or % in the URL?
789 In general unix shells, the & symbol is treated specially and when used, it
790 runs the specified command in the background. To safely send the & as a part
791 of a URL, you should quote the entire URL by using single (') or double (")
792 quotes around it. Similar problems can also occur on some shells with other
793 characters, including ?*!$~(){}<>\|;`. When in doubt, quote the URL.
795 An example that would invoke a remote CGI that uses &-symbols could be:
797 curl 'http://www.altavista.com/cgi-bin/query?text=yes&q=curl'
799 In Windows, the standard DOS shell treats the percent sign specially and you
800 need to use TWO percent signs for each single one you want to use in the
803 If you want a literal percent sign to be part of the data you pass in a POST
804 using -d/--data you must encode it as '%25' (which then also needs the
805 percent sign doubled on Windows machines).
807 4.3 How can I use {, }, [ or ] to specify multiple URLs?
809 Because those letters have a special meaning to the shell, and to be used in
810 a URL specified to curl you must quote them.
812 An example that downloads two URLs (sequentially) would do:
814 curl '{curl,www}.haxx.se'
816 To be able to use those letters as actual parts of the URL (without using
817 them for the curl URL "globbing" system), use the -g/--globoff option:
819 curl -g 'www.site.com/weirdname[].html'
821 4.4 Why do I get downloaded data even though the web page doesn't exist?
823 Curl asks remote servers for the page you specify. If the page doesn't exist
824 at the server, the HTTP protocol defines how the server should respond and
825 that means that headers and a "page" will be returned. That's simply how
828 By using the --fail option you can tell curl explicitly to not get any data
829 if the HTTP return code doesn't say success.
831 4.5 Why do I get return code XXX from a HTTP server?
833 RFC2616 clearly explains the return codes. This is a short transcript. Go
834 read the RFC for exact details:
836 4.5.1 "400 Bad Request"
838 The request could not be understood by the server due to malformed
839 syntax. The client SHOULD NOT repeat the request without modifications.
841 4.5.2 "401 Unauthorized"
843 The request requires user authentication.
845 4.5.3 "403 Forbidden"
847 The server understood the request, but is refusing to fulfil it.
848 Authorization will not help and the request SHOULD NOT be repeated.
850 4.5.4 "404 Not Found"
852 The server has not found anything matching the Request-URI. No indication
853 is given of whether the condition is temporary or permanent.
855 4.5.5 "405 Method Not Allowed"
857 The method specified in the Request-Line is not allowed for the resource
858 identified by the Request-URI. The response MUST include an Allow header
859 containing a list of valid methods for the requested resource.
861 4.5.6 "301 Moved Permanently"
863 If you get this return code and an HTML output similar to this:
865 <H1>Moved Permanently</H1> The document has moved <A
866 HREF="http://same_url_now_with_a_trailing_slash/">here</A>.
868 it might be because you request a directory URL but without the trailing
869 slash. Try the same operation again _with_ the trailing URL, or use the
870 -L/--location option to follow the redirection.
872 4.6 Can you tell me what error code 142 means?
874 All curl error codes are described at the end of the man page, in the
875 section called "EXIT CODES".
877 Error codes that are larger than the highest documented error code means
878 that curl has exited due to a crash. This is a serious error, and we
879 appreciate a detailed bug report from you that describes how we could go
880 ahead and repeat this!
882 4.7 How do I keep user names and passwords secret in Curl command lines?
884 This problem has two sides:
886 The first part is to avoid having clear-text passwords in the command line
887 so that they don't appear in 'ps' outputs and similar. That is easily
888 avoided by using the "-K" option to tell curl to read parameters from a file
889 or stdin to which you can pass the secret info. curl itself will also
890 attempt to "hide" the given password by blanking out the option - this
891 doesn't work on all platforms.
893 To keep the passwords in your account secret from the rest of the world is
894 not a task that curl addresses. You could of course encrypt them somehow to
895 at least hide them from being read by human eyes, but that is not what
896 anyone would call security.
898 Also note that regular HTTP (using Basic authentication) and FTP passwords
899 are sent in clear across the network. All it takes for anyone to fetch them
900 is to listen on the network. Eavesdropping is very easy. Use more secure
901 authentication methods (like Digest, Negotiate or even NTLM) or consider the
902 SSL-based alternatives HTTPS and FTPS.
906 It is not a bug if the behavior is documented. Read the docs first.
907 Especially check out the KNOWN_BUGS file, it may be a documented bug!
909 If it is a problem with a binary you've downloaded or a package for your
910 particular platform, try contacting the person who built the package/archive
913 If there is a bug, read the BUGS document first. Then report it as described
916 4.9 Curl can't authenticate to the server that requires NTLM?
918 NTLM support requires OpenSSL, GnuTLS, NSS, Secure Transport, or Microsoft
919 Windows libraries at build-time to provide this functionality.
921 NTLM is a Microsoft proprietary protocol. Proprietary formats are evil. You
922 should not use such ones.
924 4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!
926 Many web servers allow or demand that the administrator configures the
927 server properly for these requests to work on the web server.
929 Some servers seem to support HEAD only on certain kinds of URLs.
931 To fully grasp this, try the documentation for the particular server
932 software you're trying to interact with. This is not anything curl can do
935 4.11 Why does my HTTP range requests return the full document?
937 Because the range may not be supported by the server, or the server may
938 choose to ignore it and return the full document anyway.
940 4.12 Why do I get "certificate verify failed" ?
942 You invoke curl 7.10 or later to communicate on a https:// URL and get an
943 error back looking something similar to this:
945 curl: (35) SSL: error:14090086:SSL routines:
946 SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
948 Then it means that curl couldn't verify that the server's certificate was
949 good. Curl verifies the certificate using the CA cert bundle that comes with
950 the curl installation.
952 To disable the verification (which makes it act like curl did before 7.10),
953 use -k. This does however enable man-in-the-middle attacks.
955 If you get this failure but are having a CA cert bundle installed and used,
956 the server's certificate is not signed by one of the CA's in the bundle. It
957 might for example be self-signed. You then correct this problem by obtaining
958 a valid CA cert for the server. Or again, decrease the security by disabling
961 Details are also in the SSLCERTS file in the release archives, found online
962 here: http://curl.haxx.se/docs/sslcerts.html
964 4.13 Why is curl -R on Windows one hour off?
966 During daylight savings time, when -R is used, curl will set a time that
967 appears one hour off. This happens due to a flaw in how Windows stores and
968 uses file modification times and it is not easily worked around. For details
969 on this problem, read this: http://www.codeproject.com/datetime/dstbugs.asp
971 4.14 Redirects work in browser but not with curl!
973 curl supports HTTP redirects fine (see item 3.8). Browsers generally support
974 at least two other ways to perform redirects that curl does not:
976 Meta tags. You can write a HTML tag that will cause the browser to redirect
977 to another given URL after a certain time.
979 Javascript. You can write a Javascript program embedded in a HTML page that
980 redirects the browser to another given URL.
982 There is no way to make curl follow these redirects. You must either
983 manually figure out what the page is set to do, or you write a script that
984 parses the results and fetches the new URL.
986 4.15 FTPS doesn't work
988 curl supports FTPS (sometimes known as FTP-SSL) both implicit and explicit
991 When a URL is used that starts with FTPS://, curl assumes implicit SSL on
992 the control connection and will therefore immediately connect and try to
993 speak SSL. FTPS:// connections default to port 990.
995 To use explicit FTPS, you use a FTP:// URL and the --ftp-ssl option (or one
996 of its related flavours). This is the most common method, and the one
997 mandated by RFC4217. This kind of connection then of course uses the
998 standard FTP port 21 by default.
1000 4.16 My HTTP POST or PUT requests are slow!
1002 libcurl makes all POST and PUT requests (except for POST requests with a
1003 very tiny request body) use the "Expect: 100-continue" header. This header
1004 allows the server to deny the operation early so that libcurl can bail out
1005 already before having to send any data. This is useful in authentication
1008 However, many servers don't implement the Expect: stuff properly and if the
1009 server doesn't respond (positively) within 1 second libcurl will continue
1010 and send off the data anyway.
1012 You can disable libcurl's use of the Expect: header the same way you disable
1013 any header, using -H / CURLOPT_HTTPHEADER, or by forcing it to use HTTP 1.0.
1015 4.17 Non-functional connect timeouts
1017 In most Windows setups having a timeout longer than 21 seconds make no
1018 difference, as it will only send 3 TCP SYN packets and no more. The second
1019 packet sent three seconds after the first and the third six seconds after
1020 the second. No more than three packets are sent, no matter how long the
1023 See option TcpMaxConnectRetransmissions on this page:
1024 http://support.microsoft.com/?scid=kb%3Ben-us%3B175523&x=6&y=7
1026 Also, even on non-Windows systems there may run a firewall or anti-virus
1027 software or similar that accepts the connection but does not actually do
1028 anything else. This will make (lib)curl to consider the connection connected
1029 and thus the connect timeout won't trigger.
1031 4.18 file:// URLs containing drive letters (Windows, NetWare)
1033 When using cURL to try to download a local file, one might use a URL
1038 You'll find that even if D:\blah.txt does exist, cURL returns a 'file
1041 According to RFC 1738 (http://www.faqs.org/rfcs/rfc1738.html),
1042 file:// URLs must contain a host component, but it is ignored by
1043 most implementations. In the above example, 'D:' is treated as the
1044 host component, and is taken away. Thus, cURL tries to open '/blah.txt'.
1045 If your system is installed to drive C:, that will resolve to 'C:\blah.txt',
1046 and if that doesn't exist you will get the not found error.
1048 To fix this problem, use file:// URLs with *three* leading slashes:
1052 Alternatively, if it makes more sense, specify 'localhost' as the host
1055 file://localhost/D:/blah.txt
1057 In either case, cURL should now be looking for the correct file.
1059 4.19 Why doesn't cURL return an error when the network cable is unplugged?
1061 Unplugging a cable is not an error situation. The TCP/IP protocol stack
1062 was designed to be fault tolerant, so even though there may be a physical
1063 break somewhere the connection shouldn't be affected, just possibly
1064 delayed. Eventually, the physical break will be fixed or the data will be
1065 re-routed around the physical problem through another path.
1067 In such cases, the TCP/IP stack is responsible for detecting when the
1068 network connection is irrevocably lost. Since with some protocols it is
1069 perfectly legal for the client wait indefinitely for data, the stack may
1070 never report a problem, and even when it does, it can take up to 20 minutes
1071 for it to detect an issue. The curl option --keepalive-time enables
1072 keep-alive support in the TCP/IP stack which makes it periodically probe the
1073 connection to make sure it is still available to send data. That should
1074 reliably detect any TCP/IP network failure.
1076 But even that won't detect the network going down before the TCP/IP
1077 connection is established (e.g. during a DNS lookup) or using protocols that
1078 don't use TCP. To handle those situations, curl offers a number of timeouts
1079 on its own. --speed-limit/--speed-time will abort if the data transfer rate
1080 falls too low, and --connect-timeout and --max-time can be used to put an
1081 overall timeout on the connection phase or the entire transfer.
1083 A libcurl-using application running in a known physical environment (e.g.
1084 an embedded device with only a single network connection) may want to act
1085 immediately if its lone network connection goes down. That can be achieved
1086 by having the application monitor the network connection on its own using an
1087 OS-specific mechanism, then signalling libcurl to abort (see also item 5.13).
1092 5.1 Is libcurl thread-safe?
1096 We have written the libcurl code specifically adjusted for multi-threaded
1097 programs. libcurl will use thread-safe functions instead of non-safe ones if
1098 your system has such. Note that you must never share the same handle in
1102 If you use a OpenSSL-powered libcurl in a multi-threaded environment, you
1103 need to provide one or two locking functions:
1105 http://www.openssl.org/docs/crypto/threads.html
1107 If you use a GnuTLS-powered libcurl in a multi-threaded environment, you
1108 need to provide locking function(s) for libgcrypt (which is used by GnuTLS
1109 for the crypto functions).
1111 http://www.gnu.org/software/gnutls/manual/html_node/Multi_002dthreaded-applications.html
1113 No special locking is needed with a NSS-powered libcurl. NSS is thread-safe.
1115 5.2 How can I receive all data into a large memory chunk?
1117 [ See also the examples/getinmemory.c source ]
1119 You are in full control of the callback function that gets called every time
1120 there is data received from the remote server. You can make that callback do
1121 whatever you want. You do not have to write the received data to a file.
1123 One solution to this problem could be to have a pointer to a struct that you
1124 pass to the callback function. You set the pointer using the
1125 CURLOPT_WRITEDATA option. Then that pointer will be passed to the callback
1126 instead of a FILE * to a file:
1128 /* imaginary struct */
1129 struct MemoryStruct {
1134 /* imaginary callback function */
1136 WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data)
1138 size_t realsize = size * nmemb;
1139 struct MemoryStruct *mem = (struct MemoryStruct *)data;
1141 mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);
1143 memcpy(&(mem->memory[mem->size]), ptr, realsize);
1144 mem->size += realsize;
1145 mem->memory[mem->size] = 0;
1150 5.3 How do I fetch multiple files with libcurl?
1152 libcurl has excellent support for transferring multiple files. You should
1153 just repeatedly set new URLs with curl_easy_setopt() and then transfer it
1154 with curl_easy_perform(). The handle you get from curl_easy_init() is not
1155 only reusable, but you're even encouraged to reuse it if you can, as that
1156 will enable libcurl to use persistent connections.
1158 5.4 Does libcurl do Winsock initialization on win32 systems?
1160 Yes, if told to in the curl_global_init() call.
1162 5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?
1164 Yes, but you cannot open a FILE * and pass the pointer to a DLL and have
1165 that DLL use the FILE * (as the DLL and the client application cannot access
1166 each others' variable memory areas). If you set CURLOPT_WRITEDATA you must
1167 also use CURLOPT_WRITEFUNCTION as well to set a function that writes the
1168 file, even if that simply writes the data to the specified FILE *.
1169 Similarly, if you use CURLOPT_READDATA you must also specify
1170 CURLOPT_READFUNCTION.
1172 5.6 What about Keep-Alive or persistent connections?
1174 curl and libcurl have excellent support for persistent connections when
1175 transferring several files from the same server. Curl will attempt to reuse
1176 connections for all URLs specified on the same command line/config file, and
1177 libcurl will reuse connections for all transfers that are made using the
1178 same libcurl handle.
1180 When you use the easy interface, the connection cache is kept within the
1181 easy handle. If you instead use the multi interface, the connection cache
1182 will be kept within the multi handle and will be shared among all the easy
1183 handles that are used within the same multi handle.
1185 5.7 Link errors when building libcurl on Windows!
1187 You need to make sure that your project, and all the libraries (both static
1188 and dynamic) that it links against, are compiled/linked against the same run
1191 This is determined by the /MD, /ML, /MT (and their corresponding /M?d)
1192 options to the command line compiler. /MD (linking against MSVCRT dll) seems
1193 to be the most commonly used option.
1195 When building an application that uses the static libcurl library, you must
1196 add -DCURL_STATICLIB to your CFLAGS. Otherwise the linker will look for
1197 dynamic import symbols. If you're using Visual Studio, you need to instead
1198 add CURL_STATICLIB in the "Preprocessor Definitions" section.
1200 If you get linker error like "unknown symbol __imp__curl_easy_init ..." you
1201 have linked against the wrong (static) library. If you want to use the
1202 libcurl.dll and import lib, you don't need any extra CFLAGS, but use one of
1203 the import libraries below. These are the libraries produced by the various
1204 lib/Makefile.* files:
1206 Target: static lib. import lib for libcurl*.dll.
1207 -----------------------------------------------------------
1208 MingW: libcurl.a libcurldll.a
1209 MSVC (release): libcurl.lib libcurl_imp.lib
1210 MSVC (debug): libcurld.lib libcurld_imp.lib
1211 Borland: libcurl.lib libcurl_imp.lib
1213 5.8 libcurl.so.X: open failed: No such file or directory
1215 This is an error message you might get when you try to run a program linked
1216 with a shared version of libcurl and your run-time linker (ld.so) couldn't
1217 find the shared library named libcurl.so.X. (Where X is the number of the
1218 current libcurl ABI, typically 3 or 4).
1220 You need to make sure that ld.so finds libcurl.so.X. You can do that
1221 multiple ways, and it differs somewhat between different operating systems,
1222 but they are usually:
1224 * Add an option to the linker command line that specify the hard-coded path
1225 the run-time linker should check for the lib (usually -R)
1227 * Set an environment variable (LD_LIBRARY_PATH for example) where ld.so
1228 should check for libs
1230 * Adjust the system's config to check for libs in the directory where you've
1231 put the dir (like Linux's /etc/ld.so.conf)
1233 'man ld.so' and 'man ld' will tell you more details
1235 5.9 How does libcurl resolve host names?
1237 libcurl supports a large a number of different name resolve functions. One
1238 of them is picked at build-time and will be used unconditionally. Thus, if
1239 you want to change name resolver function you must rebuild libcurl and tell
1240 it to use a different function.
1242 - The non-ipv6 resolver that can use one out of four host name resolve calls
1243 (depending on what your system supports):
1246 B - gethostbyname_r() with 3 arguments
1247 C - gethostbyname_r() with 5 arguments
1248 D - gethostbyname_r() with 6 arguments
1250 - The ipv6-resolver that uses getaddrinfo()
1252 - The c-ares based name resolver that uses the c-ares library for resolves.
1253 Using this offers asynchronous name resolves.
1255 - The threaded resolver (default option on Windows). It uses:
1257 A - gethostbyname() on plain ipv4 hosts
1258 B - getaddrinfo() on ipv6-enabled hosts
1260 Also note that libcurl never resolves or reverse-lookups addresses given as
1261 pure numbers, such as 127.0.0.1 or ::1.
1263 5.10 How do I prevent libcurl from writing the response to stdout?
1265 libcurl provides a default built-in write function that writes received data
1266 to stdout. Set the CURLOPT_WRITEFUNCTION to receive the data, or possibly
1267 set CURLOPT_WRITEDATA to a different FILE * handle.
1269 5.11 How do I make libcurl not receive the whole HTTP response?
1271 You make the write callback (or progress callback) return an error and
1272 libcurl will then abort the transfer.
1274 5.12 Can I make libcurl fake or hide my real IP address?
1276 No. libcurl operates on a higher level. Besides, faking IP address would
1277 imply sending IP packet with a made-up source address, and then you normally
1278 get a problem with receiving the packet sent back as they would then not be
1281 If you use a proxy to access remote sites, the sites will not see your local
1282 IP address but instead the address of the proxy.
1284 Also note that on many networks NATs or other IP-munging techniques are used
1285 that makes you see and use a different IP address locally than what the
1286 remote server will see you coming from. You may also consider using
1287 http://www.torproject.org .
1289 5.13 How do I stop an ongoing transfer?
1291 With the easy interface you make sure to return the correct error code from
1292 one of the callbacks, but none of them are instant. There is no function you
1293 can call from another thread or similar that will stop it immediately.
1294 Instead, you need to make sure that one of the callbacks you use returns an
1295 appropriate value that will stop the transfer. Suitable callbacks that you
1296 can do this with include the progress callback, the read callback and the
1299 If you're using the multi interface, you can also stop a transfer by
1300 removing the particular easy handle from the multi stack at any moment you
1301 think the transfer is done or when you wish to abort the transfer.
1303 5.14 Using C++ non-static functions for callbacks?
1305 libcurl is a C library, it doesn't know anything about C++ member functions.
1307 You can overcome this "limitation" with a relative ease using a static
1308 member function that is passed a pointer to the class:
1310 // f is the pointer to your object.
1311 static YourClass::func(void *buffer, size_t sz, size_t n, void *f)
1313 // Call non-static member function.
1314 static_cast<YourClass*>(f)->nonStaticFunction();
1317 // This is how you pass pointer to the static function:
1318 curl_easy_setopt(hcurl, CURLOPT_WRITEFUNCTION, YourClass:func);
1319 curl_easy_setopt(hcurl, CURLOPT_WRITEDATA, this);
1321 5.15 How do I get an FTP directory listing?
1323 If you end the FTP URL you request with a slash, libcurl will provide you
1324 with a directory listing of that given directory. You can also set
1325 CURLOPT_CUSTOMREQUEST to alter what exact listing command libcurl would use
1328 The follow-up question that tend to follow the previous one, is how a
1329 program is supposed to parse the directory listing. How does it know what's
1330 a file and what's a dir and what's a symlink etc. The harsh reality is that
1331 FTP provides no such fine and easy-to-parse output. The output format FTP
1332 servers respond to LIST commands are entirely at the server's own liking and
1333 the NLST output doesn't reveal any types and in many cases don't even
1334 include all the directory entries. Also, both LIST and NLST tend to hide
1335 unix-style hidden files (those that start with a dot) by default so you need
1336 to do "LIST -a" or similar to see them.
1338 The application thus needs to parse the LIST output. One such existing
1339 list parser is available at http://cr.yp.to/ftpparse.html Versions of
1340 libcurl since 7.21.0 also provide the ability to specify a wildcard to
1341 download multiple files from one FTP directory.
1343 5.16 I want a different time-out!
1345 Time and time again users realize that CURLOPT_TIMEOUT and
1346 CURLOPT_CONNECTIMEOUT are not sufficiently advanced or flexible to cover all
1347 the various use cases and scenarios applications end up with.
1349 libcurl offers many more ways to time-out operations. A common alternative
1350 is to use the CURLOPT_LOW_SPEED_LIMIT and CURLOPT_LOW_SPEED_TIME options to
1351 specify the lowest possible speed to accept before to consider the transfer
1354 The most flexible way is by writing your own time-out logic and using
1355 CURLOPT_PROGRESSFUNCTION (perhaps in combination with other callbacks) and
1356 use that to figure out exactly when the right condition is met when the
1357 transfer should get stopped.
1359 5.17 Can I write a server with libcurl?
1361 No. libcurl offers no functions or building blocks to build any kind of
1362 internet protocol server. libcurl is only a client-side library. For server
1363 libraries, you need to continue your search elsewhere but there exist many
1364 good open source ones out there for most protocols you could possibly want a
1365 server for. And there are really good stand-alone ones that have been tested
1366 and proven for many years. There's no need for you to reinvent them!
1371 Curl and libcurl are released under a MIT/X derivate license. The license is
1372 very liberal and should not impose a problem for your project. This section
1373 is just a brief summary for the cases we get the most questions. (Parts of
1374 this section was much enhanced by Bjorn Reese.)
1376 We are not lawyers and this is not legal advice. You should probably consult
1377 one if you want true and accurate legal insights without our prejudice. Note
1378 especially that this section concerns the libcurl license only; compiling in
1379 features of libcurl that depend on other libraries (e.g. OpenSSL) may affect
1380 the licensing obligations of your application.
1382 6.1 I have a GPL program, can I use the libcurl library?
1386 Since libcurl may be distributed under the MIT/X derivate license, it can be
1387 used together with GPL in any software.
1389 6.2 I have a closed-source program, can I use the libcurl library?
1393 libcurl does not put any restrictions on the program that uses the library.
1395 6.3 I have a BSD licensed program, can I use the libcurl library?
1399 libcurl does not put any restrictions on the program that uses the library.
1401 6.4 I have a program that uses LGPL libraries, can I use libcurl?
1405 The LGPL license doesn't clash with other licenses.
1407 6.5 Can I modify curl/libcurl for my program and keep the changes secret?
1411 The MIT/X derivate license practically allows you to do almost anything with
1412 the sources, on the condition that the copyright texts in the sources are
1415 6.6 Can you please change the curl/libcurl license to XXXX?
1419 We have carefully picked this license after years of development and
1420 discussions and a large amount of people have contributed with source code
1421 knowing that this is the license we use. This license puts the restrictions
1422 we want on curl/libcurl and it does not spread to other programs or
1423 libraries that use it. It should be possible for everyone to use libcurl or
1424 curl in their projects, no matter what license they already have in use.
1426 6.7 What are my obligations when using libcurl in my commercial apps?
1428 Next to none. All you need to adhere to is the MIT-style license (stated in
1429 the COPYING file) which basically says you have to include the copyright
1430 notice in "all copies" and that you may not use the copyright holder's name
1431 when promoting your software.
1433 You do not have to release any of your source code.
1435 You do not have to reveal or make public any changes to the libcurl source
1438 You do not have to broadcast to the world that you are using libcurl within
1441 All we ask is that you disclose "the copyright notice and this permission
1442 notice" somewhere. Most probably like in the documentation or in the section
1443 where other third party dependencies already are mentioned and acknowledged.
1445 As can be seen here: http://curl.haxx.se/docs/companies.html and elsewhere,
1446 more and more companies are discovering the power of libcurl and take
1447 advantage of it even in commercial environments.
1452 7.1 What is PHP/CURL?
1454 The module for PHP that makes it possible for PHP programs to access curl-
1455 functions from within PHP.
1457 In the cURL project we call this module PHP/CURL to differentiate it from
1458 curl the command line tool and libcurl the library. The PHP team however
1459 does not refer to it like this (for unknown reasons). They call it plain
1460 CURL (often using all caps) or sometimes ext/curl, but both cause much
1461 confusion to users which in turn gives us a higher question load.
1463 7.2 Who wrote PHP/CURL?
1465 PHP/CURL is a module that comes with the regular PHP package. It depends and
1466 uses libcurl, so you need to have libcurl installed properly first before
1467 PHP/CURL can be used. PHP/CURL was initially written by Sterling Hughes.
1469 7.3 Can I perform multiple requests using the same handle?
1471 Yes - at least in PHP version 4.3.8 and later (this has been known to not
1472 work in earlier versions, but the exact version when it started to work is
1475 After a transfer, you just set new options in the handle and make another
1476 transfer. This will make libcurl to re-use the same connection if it can.