1 Updated: September 7, 2010 (http://curl.haxx.se/docs/faq.html)
6 \___|\___/|_| \_\_____|
14 1.4 When will you make curl do XXXX ?
16 1.6 What do you get for making curl?
17 1.7 What about CURL from curl.com?
18 1.8 I have a problem who do I mail?
19 1.9 Where do I buy commercial support for curl?
20 1.10 How many are using curl?
21 1.11 Why don't you update ca-bundle.crt
22 1.12 I have a problem who can I chat with?
23 1.13 curl's ECCN number?
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 Pragma: nocache 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?
55 4.1 Problems connecting to SSL servers.
56 4.2 Why do I get problems when I use & or % in the URL?
57 4.3 How can I use {, }, [ or ] to specify multiple URLs?
58 4.4 Why do I get downloaded data even though the web page doesn't exist?
59 4.5 Why do I get return code XXX from a HTTP server?
60 4.5.1 "400 Bad Request"
61 4.5.2 "401 Unauthorized"
64 4.5.5 "405 Method Not Allowed"
65 4.5.6 "301 Moved Permanently"
66 4.6 Can you tell me what error code 142 means?
67 4.7 How do I keep user names and passwords secret in Curl command lines?
69 4.9 Curl can't authenticate to the server that requires NTLM?
70 4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!
71 4.11 Why does my HTTP range requests return the full document?
72 4.12 Why do I get "certificate verify failed" ?
73 4.13 Why is curl -R on Windows one hour off?
74 4.14 Redirects work in browser but not with curl!
75 4.15 FTPS doesn't work
76 4.16 My HTTP POST or PUT requests are slow!
77 4.17 Non-functional connect timeouts on Windows
78 4.18 file:// URLs containing drive letters (Windows, NetWare)
79 4.19 Why doesn't cURL return an error when the network cable is unplugged?
82 5.1 Is libcurl thread-safe?
83 5.2 How can I receive all data into a large memory chunk?
84 5.3 How do I fetch multiple files with libcurl?
85 5.4 Does libcurl do Winsock initing on win32 systems?
86 5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?
87 5.6 What about Keep-Alive or persistent connections?
88 5.7 Link errors when building libcurl on Windows!
89 5.8 libcurl.so.X: open failed: No such file or directory
90 5.9 How does libcurl resolve host names?
91 5.10 How do I prevent libcurl from writing the response to stdout?
92 5.11 How do I make libcurl not receive the whole HTTP response?
93 5.12 Can I make libcurl fake or hide my real IP address?
94 5.13 How do I stop an ongoing transfer?
95 5.14 Using C++ non-static functions for callbacks?
96 5.15 How do I get an FTP directory listing?
99 6.1 I have a GPL program, can I use the libcurl library?
100 6.2 I have a closed-source program, can I use the libcurl library?
101 6.3 I have a BSD licensed program, can I use the libcurl library?
102 6.4 I have a program that uses LGPL libraries, can I use libcurl?
103 6.5 Can I modify curl/libcurl for my program and keep the changes secret?
104 6.6 Can you please change the curl/libcurl license to XXXX?
105 6.7 What are my obligations when using libcurl in my commercial apps?
108 7.1 What is PHP/CURL?
109 7.2 Who write PHP/CURL?
110 7.3 Can I perform multiple requests using the same handle?
112 ==============================================================================
118 cURL is the name of the project. The name is a play on 'Client for URLs',
119 originally with URL spelled in uppercase to make it obvious it deals with
120 URLs. The fact it can also be pronounced 'see URL' also helped, it works as
121 an abbreviation for "Client URL Request Library" or why not the recursive
122 version: "Curl URL Request Library".
124 The cURL project produces two products:
128 A free and easy-to-use client-side URL transfer library, supporting DICT,
129 FILE, FTP, FTPS, GOPHER, HTTP, HTTPS, IMAP, IMAPS, LDAP, LDAPS, POP3,
130 POP3S, RTMP, RTSP, SCP, SFTP, SMTP, SMTPS, TELNET and TFTP.
132 libcurl supports HTTPS certificates, HTTP POST, HTTP PUT, FTP uploading,
133 kerberos, HTTP form based upload, proxies, cookies, user+password
134 authentication, file transfer resume, http proxy tunneling and more!
136 libcurl is highly portable, it builds and works identically on numerous
137 platforms, including Solaris, NetBSD, FreeBSD, OpenBSD, Darwin, HPUX,
138 IRIX, AIX, Tru64, Linux, UnixWare, HURD, Windows, Amiga, OS/2, BeOs, Mac
139 OS X, Ultrix, QNX, OpenVMS, RISC OS, Novell NetWare, DOS, Symbian, OSF,
140 Android, Minix, IBM TPF and more...
142 libcurl is free, thread-safe, IPv6 compatible, feature rich, well
147 A command line tool for getting or sending files using URL syntax.
149 Since curl uses libcurl, curl supports the same wide range of common
150 Internet protocols that libcurl does.
152 We pronounce curl and cURL with an initial k sound: [kurl].
154 There are numerous sub-projects and related projects that also use the word
155 curl in the project names in various combinations, but you should take
156 notice that this FAQ is directed at the command-line tool named curl (and
157 libcurl the library), and may therefore not be valid for other curl-related
158 projects. (There is however a small section for the PHP/CURL in this FAQ.)
162 libcurl is a reliable and portable library which provides you with an easy
163 interface to a range of common Internet protocols.
165 You can use libcurl for free in your application, be it open source,
166 commercial or closed-source.
168 libcurl is most probably the most portable, most powerful and most often
169 used C-based multi-platform file transfer library on this planet - be it
170 open source or commercial.
172 1.3 What is curl not?
174 Curl is not a wget clone. That is a common misconception. Never, during
175 curl's development, have we intended curl to replace wget or compete on its
176 market. Curl is targeted at single-shot file transfers.
178 Curl is not a web site mirroring program. If you want to use curl to mirror
179 something: fine, go ahead and write a script that wraps around curl to make
180 it reality (like curlmirror.pl does).
182 Curl is not an FTP site mirroring program. Sure, get and send FTP with curl
183 but if you want systematic and sequential behavior you should write a
184 script (or write a new program that interfaces libcurl) and do it.
186 Curl is not a PHP tool, even though it works perfectly well when used from
187 or with PHP (when using the PHP/CURL module).
189 Curl is not a program for a single operating system. Curl exists, compiles,
190 builds and runs under a wide range of operating systems, including all
191 modern Unixes (and a bunch of older ones too), Windows, Amiga, BeOS, OS/2,
194 1.4 When will you make curl do XXXX ?
196 We love suggestions of what to change in order to make curl and libcurl
197 better. We do however believe in a few rules when it comes to the future of
200 * Curl -- the command line tool -- is to remain a non-graphical command line
201 tool. If you want GUIs or fancy scripting capabilities, you should look
202 for another tool that uses libcurl.
204 * We do not add things to curl that other small and available tools already
205 do very fine at the side. Curl's output is fine to pipe into another
206 program or redirect to another file for the next program to interpret.
208 * We focus on protocol related issues and improvements. If you wanna do more
209 magic with the supported protocols than curl currently does, chances are
210 big we will agree. If you wanna add more protocols, we may very well
213 * If you want someone else to make all the work while you wait for us to
214 implement it for you, that is not a very friendly attitude. We spend a
215 considerable time already on maintaining and developing curl. In order to
216 get more out of us, you should consider trading in some of your time and
219 * If you write the code, chances are bigger that it will get into curl
224 curl and libcurl are not made by any single individual. Daniel Stenberg is
225 project leader and main developer, but other persons' submissions are
226 important and crucial. Anyone can contribute and post their changes and
227 improvements and have them inserted in the main sources (of course on the
228 condition that developers agree on that the fixes are good).
230 The full list of all contributors is found in the docs/THANKS file.
232 curl is developed by a community, with Daniel at the wheel.
234 1.6 What do you get for making curl?
236 Project cURL is entirely free and open. No person gets paid for developing
237 (lib)curl on full or even part time. We do this voluntarily on our spare
238 time. Occasionally companies pay individual developers to work on curl, but
239 that's up to each company and developer. It is not controlled by nor
240 supervised in any way by the project.
242 We still get help from companies. Haxx provides web site, bandwidth, mailing
243 lists etc and sourceforge.net hosts project services we take advantage from,
244 like the bug tracker. Also again, some companies have sponsored certain
245 parts of the development in the past and I hope some will continue to do so
248 If you want to support our project, consider a donation or a banner-program
249 or even better: by helping us coding, documenting, testing etc.
251 1.7 What about CURL from curl.com?
253 During the summer 2001, curl.com was busy advertising their client-side
254 programming language for the web, named CURL.
256 We are in no way associated with curl.com or their CURL programming
259 Our project name curl has been in effective use since 1998. We were not the
260 first computer related project to use the name "curl" and do not claim any
261 first-hand rights to the name.
263 We recognize that we will be living in parallel with curl.com and wish them
266 1.8 I have a problem who do I mail?
268 Please do not mail any single individual unless you really need to. Keep
269 curl-related questions on a suitable mailing list. All available mailing
270 lists are listed in the MANUAL document and online at
271 http://curl.haxx.se/mail/
273 Keeping curl-related questions and discussions on mailing lists allows
274 others to join in and help, to share their ideas, contribute their
275 suggestions and spread their wisdom. Keeping discussions on public mailing
276 lists also allows for others to learn from this (both current and future
277 users thanks to the web based archives of the mailing lists), thus saving us
278 from having to repeat ourselves even more. Thanks for respecting this.
280 If you have found or simply suspect a security problem in curl or libcurl,
281 mail curl-security at haxx.se (closed list of receivers, mails are not
282 disclosed) and tell. Then we can produce a fix in a timely manner before the
283 flaw is announced to the world, thus lessen the impact the problem will have
286 1.9 Where do I buy commercial support for curl?
288 curl is fully open source. It means you can hire any skilled engineer to fix
289 your curl-related problems.
291 We list available alternatives on the curl web site:
292 http://curl.haxx.se/support.html
294 1.10 How many are using curl?
296 It is impossible to tell.
298 We don't know how many users that knowingly have installed and use curl.
300 We don't know how many users that use curl without knowing that they are in
303 We don't know how many users that downloaded or installed curl and then
306 Some facts to use as input to the math:
308 curl packages are downloaded from the curl.haxx.se and mirrors over a
309 million times per year. curl is installed by default with most Linux
310 distributions. curl is installed by default with Mac OS X. curl and libcurl
311 as used by numerous applications that include libcurl binaries in their
312 distribution packages (like Adobe Acrobat Reader and Google Earth).
314 More than a hundred known named companies use curl in commercial
315 environments and products and more than a hundred known named open source
316 projects depend on (lib)curl.
318 In a poll on the curl web site mid-2005, more than 50% of the 300+ answers
319 estimated a user base of one million users or more.
321 In March 2005, the "Linux Counter project" estimated a total Linux user base
322 of some 29 millions, while Netcraft detected some 4 million "active" Linux
323 based web servers. A guess is that a fair amount of these Linux
324 installations have curl installed.
326 All this taken together, there is no doubt that there are millions of
329 http://curl.haxx.se/docs/companies.html
330 http://curl.haxx.se/docs/programs.html
331 http://curl.haxx.se/libcurl/using/apps.html
332 http://counter.li.org/estimates.php
333 http://news.netcraft.com/archives/2005/03/14/fedora_makes_rapid_progress.html
335 1.11 Why don't you update ca-bundle.crt
337 The ca-bundle.crt file that used to be bundled with curl was very outdated
338 (it being last modified year 2000 should tell) and must be replaced with a
339 much more modern and up-to-date version by anyone who wants to verify peers
340 anyway. It is no longer provided, the last curl release that shipped it was
343 In the cURL project we've decided not to attempt to keep this file updated
344 (or even present anymore) since deciding what to add to a ca cert bundle is
345 an undertaking we've not been ready to accept, and the one we can get from
346 Mozilla is perfectly fine so there's no need to duplicate that work.
348 Today, with many services performed over HTTPS, every operating system
349 should come with a default ca cert bundle that can be deemed somewhat
350 trustworthy and that collection (if reasonably updated) should be deemed to
351 be a lot better than a private curl version.
353 If you want the most recent collection of ca certs that Mozilla Firefox
354 uses, we recommend that you extract the collection yourself from Mozilla
355 Firefox (by running 'make ca-bundle), or by using our online service setup
356 for this purpose: http://curl.haxx.se/docs/caextract.html
358 1.12 I have a problem who can I chat with?
360 There's a bunch of friendly people hanging out in the #curl channel on the
361 IRC network irc.freenode.net. If you're polite and nice, chances are big
362 that you can get -- or provide -- help instantly.
364 1.13 curl's ECCN number?
366 The US government restricts exports of software that contains or uses
367 cryptography. When doing so, the Export Control Classification Number (ECCN)
368 is used to identify the level of export control etc.
370 ASF gives a good explanation at http://www.apache.org/dev/crypto.html
372 We believe curl's number might be ECCN 5D002, another possibility is
373 5D992. It seems necessary to write them, asking to confirm.
375 Comprehensible explanations of the meaning of such numbers and how to
376 obtain them (resp.) are here
378 http://www.bis.doc.gov/licensing/exportingbasics.htm
379 http://www.bis.doc.gov/licensing/do_i_needaneccn.html
381 An incomprehensible description of the two numbers above is here
382 http://www.access.gpo.gov/bis/ear/pdf/ccl5-pt2.pdf
385 2. Install Related Problems
387 2.1 configure doesn't find OpenSSL even when it is installed
389 This may be because of several reasons.
391 2.1.1 native linker doesn't find openssl
394 Solaris (native cc compiler)
395 HPUX (native cc compiler)
396 SGI IRIX (native cc compiler)
397 SCO UNIX (native cc compiler)
399 When configuring curl, I specify --with-ssl. OpenSSL is installed in
400 /usr/local/ssl Configure reports SSL in /usr/local/ssl, but fails to find
401 CRYPTO_lock in -lcrypto
403 Cause: The cc for this test places the -L/usr/local/ssl/lib AFTER
404 -lcrypto, so ld can't find the library. This is due to a bug in the GNU
407 Workaround: Specifying "LDFLAGS=-L/usr/local/ssl/lib" in front of
408 ./configure places the -L/usr/local/ssl/lib early enough in the command
409 line to make things work
411 2.1.2 only the libssl lib is missing
413 If all include files and the libcrypto lib is present, with only the
414 libssl being missing according to configure, this is mostly likely because
415 a few functions are left out from the libssl.
417 If the function names missing include RSA or RSAREF you can be certain
418 that this is because libssl requires the RSA and RSAREF libs to build.
420 See the INSTALL file section that explains how to add those libs to
421 configure. Make sure that you remove the config.cache file before you
422 rerun configure with the new flags.
424 2.2 Does curl work/build with other SSL libraries?
426 Curl has been written to use OpenSSL, GnuTLS, yassl, NSS or PolarSSL,
427 although there should not be many problems using a different library. If
428 anyone does "port" curl to use a different SSL library, we are of course
429 very interested in getting the patch!
431 2.3 Where can I find a copy of LIBEAY32.DLL?
433 That is an OpenSSL binary built for Windows.
435 Curl uses OpenSSL to do the SSL stuff. The LIBEAY32.DLL is what curl needs
436 on a windows machine to do https://. Check out the curl web site to find
437 accurate and up-to-date pointers to recent OpenSSL DLLs and other binary
440 2.4 Does curl support SOCKS (RFC 1928) ?
442 Yes, SOCKS 4 and 5 are supported.
447 3.1 curl: (1) SSL is disabled, https: not supported
449 If you get this output when trying to get anything from a https:// server,
450 it means that the configure script couldn't find all libs and include files
451 it requires for SSL to work. If the configure script fails to find them,
452 curl is simply built without SSL support.
454 To get the https:// support into a curl that was previously built but that
455 reports that https:// is not supported, you should dig through the document
456 and logs and check out why the configure script doesn't find the SSL libs
457 and/or include files.
459 Also, check out the other paragraph in this FAQ labelled "configure doesn't
460 find OpenSSL even when it is installed".
462 3.2 How do I tell curl to resume a transfer?
464 Curl supports resumed transfers both ways on both FTP and HTTP.
468 3.3 Why doesn't my posting using -F work?
470 You can't simply use -F or -d at your choice. The web server that will
471 receive your post assumes one of the formats. If the form you're trying to
472 "fake" sets the type to 'multipart/form-data', then and only then you must
473 use the -F type. In all the most common cases, you should use -d which then
474 causes a posting with the type 'application/x-www-form-urlencoded'.
476 This is described in some detail in the MANUAL and TheArtOfHttpScripting
477 documents, and if you don't understand it the first time, read it again
478 before you post questions about this to the mailing list. Also, try reading
479 through the mailing list archives for old postings and questions regarding
482 3.4 How do I tell curl to run custom FTP commands?
484 You can tell curl to perform optional commands both before and/or after a
485 file transfer. Study the -Q/--quote option.
487 Since curl is used for file transfers, you don't use curl to just perform
488 FTP commands without transferring anything. Therefore you must always specify
489 a URL to transfer to/from even when doing custom FTP commands.
491 3.5 How can I disable the Pragma: nocache header?
493 You can change all internally generated headers by adding a replacement with
494 the -H/--header option. By adding a header with empty contents you safely
495 disable that one. Use -H "Pragma:" to disable that specific header.
497 3.6 Does curl support ASP, XML, XHTML or HTML version Y?
499 To curl, all contents are alike. It doesn't matter how the page was
500 generated. It may be ASP, PHP, Perl, shell-script, SSI or plain
501 HTML-files. There's no difference to curl and it doesn't even know what kind
502 of language that generated the page.
504 See also item 3.14 regarding javascript.
506 3.7 Can I use curl to delete/rename a file through FTP?
508 Yes. You specify custom FTP commands with -Q/--quote.
510 One example would be to delete a file after you have downloaded it:
512 curl -O ftp://download.com/coolfile -Q '-DELE coolfile'
514 or rename a file after upload:
516 curl -T infile ftp://upload.com/dir/ -Q "-RNFR infile" -Q "-RNTO newname"
518 3.8 How do I tell curl to follow HTTP redirects?
520 Curl does not follow so-called redirects by default. The Location: header
521 that informs the client about this is only interpreted if you're using the
522 -L/--location option. As in:
524 curl -L http://redirector.com
526 Not all redirects are HTTP ones, see 4.14
528 3.9 How do I use curl in my favorite programming language?
530 There exist many language interfaces/bindings for curl that integrates it
531 better with various languages. If you are fluid in a script language, you
532 may very well opt to use such an interface instead of using the command line
535 Find out more about which languages that support curl directly, and how to
536 install and use them, in the libcurl section of the curl web site:
537 http://curl.haxx.se/libcurl/
539 In October 2009, there were interfaces available for the following
540 languages: Ada95, Basic, C, C++, Ch, Cocoa, D, Dylan, Eiffel, Euphoria,
541 Ferite, Gambas, glib/GTK+, Haskell, ILE/RPG, Java, Lisp, Lua, Mono, .NET,
542 Object-Pascal, O'Caml, Pascal, Perl, PHP, PostgreSQL, Python, R, Rexx, Ruby,
543 Scheme, S-Lang, Smalltalk, SP-Forth, SPL, Tcl, Visual Basic, Visual FoxPro,
544 Q, wxwidgets and XBLite. By the time you read this, additional ones may have
547 3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP?
549 Curl adheres to the HTTP spec, which basically means you can play with *any*
550 protocol that is built on top of HTTP. Protocols such as SOAP, WEBDAV and
551 XML-RPC are all such ones. You can use -X to set custom requests and -H to
552 set custom headers (or replace internally generated ones).
554 Using libcurl is of course just as fine and you'd just use the proper
555 library options to do the same.
557 3.11 How do I POST with a different Content-Type?
559 You can always replace the internally generated headers with -H/--header.
560 To make a simple HTTP POST with text/xml as content-type, do something like:
562 curl -d "datatopost" -H "Content-Type: text/xml" [URL]
564 3.12 Why do FTP specific features over HTTP proxy fail?
566 Because when you use a HTTP proxy, the protocol spoken on the network will
567 be HTTP, even if you specify a FTP URL. This effectively means that you
568 normally can't use FTP specific features such as FTP upload and FTP quote
571 There is one exception to this rule, and that is if you can "tunnel through"
572 the given HTTP proxy. Proxy tunneling is enabled with a special option (-p)
573 and is generally not available as proxy admins usually disable tunneling to
574 other ports than 443 (which is used for HTTPS access through proxies).
576 3.13 Why does my single/double quotes fail?
578 To specify a command line option that includes spaces, you might need to
579 put the entire option within quotes. Like in:
581 curl -d " with spaces " url.com
585 curl -d ' with spaces ' url.com
587 Exactly what kind of quotes and how to do this is entirely up to the shell
588 or command line interpreter that you are using. For most unix shells, you
589 can more or less pick either single (') or double (") quotes. For
590 Windows/DOS prompts I believe you're forced to use double (") quotes.
592 Please study the documentation for your particular environment. Examples in
593 the curl docs will use a mix of both these ones as shown above. You must
594 adjust them to work in your environment.
596 Remember that curl works and runs on more operating systems than most single
597 individuals have ever tried.
599 3.14 Does curl support Javascript or PAC (automated proxy config)?
601 Many web pages do magic stuff using embedded Javascript. Curl and libcurl
602 have no built-in support for that, so it will be treated just like any other
605 .pac files are a netscape invention and are sometimes used by organizations
606 to allow them to differentiate which proxies to use. The .pac contents is
607 just a Javascript program that gets invoked by the browser and that returns
608 the name of the proxy to connect to. Since curl doesn't support Javascript,
609 it can't support .pac proxy configuration either.
611 Some workarounds usually suggested to overcome this Javascript dependency:
613 - Depending on the Javascript complexity, write up a script that
614 translates it to another language and execute that.
616 - Read the Javascript code and rewrite the same logic in another language.
618 - Implement a Javascript interpreter, people have successfully used the
619 Mozilla Javascript engine in the past.
621 - Ask your admins to stop this, for a static proxy setup or similar.
623 3.15 Can I do recursive fetches with curl?
625 No. curl itself has no code that performs recursive operations, such as
626 those performed by wget and similar tools.
628 There exist wrapper scripts with that functionality (for example the
629 curlmirror perl script), and you can write programs based on libcurl to do
630 it, but the command line tool curl itself cannot.
632 3.16 What certificates do I need when I use SSL?
634 There are three different kinds of "certificates" to keep track of when we
635 talk about using SSL-based protocols (HTTPS or FTPS) using curl or libcurl.
637 - Client certificate. The server you communicate may require that you can
638 provide this in order to prove that you actually are who you claim to be.
639 If the server doesn't require this, you don't need a client certificate.
641 A client certificate is always used together with a private key, and the
642 private key has a pass phrase that protects it.
644 - Server certificate. The server you communicate with has a server
645 certificate. You can and should verify this certificate to make sure that
646 you are truly talking to the real server and not a server impersonating
649 - Certificate Authority certificate ("CA cert"). You often have several CA
650 certs in a CA cert bundle that can be used to verify a server certificate
651 that was signed by one of the authorities in the bundle. curl does not
652 come with a CA cert bundle but most curl installs provide one. You can
653 also override the default.
655 The server certificate verification process is made by using a Certificate
656 Authority certificate ("CA cert") that was used to sign the server
657 certificate. Server certificate verification is enabled by default in curl
658 and libcurl and is often the reason for problems as explained in FAQ entry
659 4.12 and the SSLCERTS document
660 (http://curl.haxx.se/docs/sslcerts.html). Server certificates that are
661 "self-signed" or otherwise signed by a CA that you do not have a CA cert
662 for, cannot be verified. If the verification during a connect fails, you
663 are refused access. You then need to explicitly disable the verification
664 to connect to the server.
666 3.17 How do I list the root dir of an FTP server?
668 There are two ways. The way defined in the RFC is to use an encoded slash
669 in the first path part. List the "/tmp" dir like this:
671 curl ftp://ftp.sunet.se/%2ftmp/
673 or the not-quite-kosher-but-more-readable way, by simply starting the path
674 section of the URL with a slash:
676 curl ftp://ftp.sunet.se//tmp/
678 3.18 Can I use curl to send a POST/PUT and not wait for a response?
682 But you could easily write your own program using libcurl to do such stunts.
684 3.19 How do I get HTTP from a host using a specific IP address?
686 For example, you may be trying out a web site installation that isn't yet in
687 the DNS. Or you have a site using multiple IP addresses for a given host
688 name and you want to address a specific one out of the set.
690 Set a custom Host: header that identifies the server name you want to reach
691 but use the target IP address in the URL:
693 curl --header "Host: www.example.com" http://127.0.0.1/
698 4.1 Problems connecting to SSL servers.
700 It took a very long time before we could sort out why curl had problems to
701 connect to certain SSL servers when using SSLeay or OpenSSL v0.9+. The
702 error sometimes showed up similar to:
704 16570:error:1407D071:SSL routines:SSL2_READ:bad mac decode:s2_pkt.c:233:
706 It turned out to be because many older SSL servers don't deal with SSLv3
707 requests properly. To correct this problem, tell curl to select SSLv2 from
708 the command line (-2/--sslv2).
710 There have also been examples where the remote server didn't like the SSLv2
711 request and instead you had to force curl to use SSLv3 with -3/--sslv3.
713 4.2 Why do I get problems when I use & or % in the URL?
715 In general unix shells, the & symbol is treated specially and when used, it
716 runs the specified command in the background. To safely send the & as a part
717 of a URL, you should quote the entire URL by using single (') or double (")
718 quotes around it. Similar problems can also occur on some shells with other
719 characters, including ?*!$~(){}<>\|;`. When in doubt, quote the URL.
721 An example that would invoke a remote CGI that uses &-symbols could be:
723 curl 'http://www.altavista.com/cgi-bin/query?text=yes&q=curl'
725 In Windows, the standard DOS shell treats the %-symbol specially and you
726 need to use TWO %-symbols for each single one you want to use in the URL.
728 Also note that if you want the literal %-symbol to be part of the data you
729 pass in a POST using -d/--data you must encode it as '%25' (which then also
730 needs the %-symbol doubled on Windows machines).
732 4.3 How can I use {, }, [ or ] to specify multiple URLs?
734 Because those letters have a special meaning to the shell, and to be used in
735 a URL specified to curl you must quote them.
737 An example that downloads two URLs (sequentially) would do:
739 curl '{curl,www}.haxx.se'
741 To be able to use those letters as actual parts of the URL (without using
742 them for the curl URL "globbing" system), use the -g/--globoff option:
744 curl -g 'www.site.com/weirdname[].html'
746 4.4 Why do I get downloaded data even though the web page doesn't exist?
748 Curl asks remote servers for the page you specify. If the page doesn't exist
749 at the server, the HTTP protocol defines how the server should respond and
750 that means that headers and a "page" will be returned. That's simply how
753 By using the --fail option you can tell curl explicitly to not get any data
754 if the HTTP return code doesn't say success.
756 4.5 Why do I get return code XXX from a HTTP server?
758 RFC2616 clearly explains the return codes. This is a short transcript. Go
759 read the RFC for exact details:
761 4.5.1 "400 Bad Request"
763 The request could not be understood by the server due to malformed
764 syntax. The client SHOULD NOT repeat the request without modifications.
766 4.5.2 "401 Unauthorized"
768 The request requires user authentication.
770 4.5.3 "403 Forbidden"
772 The server understood the request, but is refusing to fulfill it.
773 Authorization will not help and the request SHOULD NOT be repeated.
775 4.5.4 "404 Not Found"
777 The server has not found anything matching the Request-URI. No indication
778 is given of whether the condition is temporary or permanent.
780 4.5.5 "405 Method Not Allowed"
782 The method specified in the Request-Line is not allowed for the resource
783 identified by the Request-URI. The response MUST include an Allow header
784 containing a list of valid methods for the requested resource.
786 4.5.6 "301 Moved Permanently"
788 If you get this return code and an HTML output similar to this:
790 <H1>Moved Permanently</H1> The document has moved <A
791 HREF="http://same_url_now_with_a_trailing_slash/">here</A>.
793 it might be because you request a directory URL but without the trailing
794 slash. Try the same operation again _with_ the trailing URL, or use the
795 -L/--location option to follow the redirection.
797 4.6 Can you tell me what error code 142 means?
799 All curl error codes are described at the end of the man page, in the
800 section called "EXIT CODES".
802 Error codes that are larger than the highest documented error code means
803 that curl has exited due to a crash. This is a serious error, and we
804 appreciate a detailed bug report from you that describes how we could go
805 ahead and repeat this!
807 4.7 How do I keep user names and passwords secret in Curl command lines?
809 This problem has two sides:
811 The first part is to avoid having clear-text passwords in the command line
812 so that they don't appear in 'ps' outputs and similar. That is easily
813 avoided by using the "-K" option to tell curl to read parameters from a file
814 or stdin to which you can pass the secret info. curl itself will also
815 attempt to "hide" the given password by blanking out the option - this
816 doesn't work on all platforms.
818 To keep the passwords in your account secret from the rest of the world is
819 not a task that curl addresses. You could of course encrypt them somehow to
820 at least hide them from being read by human eyes, but that is not what
821 anyone would call security.
823 Also note that regular HTTP (using Basic authentication) and FTP passwords
824 are sent in clear across the network. All it takes for anyone to fetch them
825 is to listen on the network. Eavesdropping is very easy. Use more secure
826 authentication methods (like Digest, Negotiate or even NTLM) or consider the
827 SSL-based alternatives HTTPS and FTPS.
831 It is not a bug if the behavior is documented. Read the docs first.
832 Especially check out the KNOWN_BUGS file, it may be a documented bug!
834 If it is a problem with a binary you've downloaded or a package for your
835 particular platform, try contacting the person who built the package/archive
838 If there is a bug, read the BUGS document first. Then report it as described
841 4.9 Curl can't authenticate to the server that requires NTLM?
843 NTLM support requires OpenSSL, GnuTLS, NSS or Microsoft Windows libraries at
844 build-time to provide this functionality.
846 NTLM is a Microsoft proprietary protocol. Proprietary formats are evil. You
847 should not use such ones.
849 4.10 My HTTP request using HEAD, PUT or DELETE doesn't work!
851 Many web servers allow or demand that the administrator configures the
852 server properly for these requests to work on the web server.
854 Some servers seem to support HEAD only on certain kinds of URLs.
856 To fully grasp this, try the documentation for the particular server
857 software you're trying to interact with. This is not anything curl can do
860 4.11 Why does my HTTP range requests return the full document?
862 Because the range may not be supported by the server, or the server may
863 choose to ignore it and return the full document anyway.
865 4.12 Why do I get "certificate verify failed" ?
867 You invoke curl 7.10 or later to communicate on a https:// URL and get an
868 error back looking something similar to this:
870 curl: (35) SSL: error:14090086:SSL routines:
871 SSL3_GET_SERVER_CERTIFICATE:certificate verify failed
873 Then it means that curl couldn't verify that the server's certificate was
874 good. Curl verifies the certificate using the CA cert bundle that comes with
875 the curl installation.
877 To disable the verification (which makes it act like curl did before 7.10),
878 use -k. This does however enable man-in-the-middle attacks.
880 If you get this failure but are having a CA cert bundle installed and used,
881 the server's certificate is not signed by one of the CA's in the bundle. It
882 might for example be self-signed. You then correct this problem by obtaining
883 a valid CA cert for the server. Or again, decrease the security by disabling
886 Details are also in the SSLCERTS file in the release archives, found online
887 here: http://curl.haxx.se/docs/sslcerts.html
889 4.13 Why is curl -R on Windows one hour off?
891 During daylight savings time, when -R is used, curl will set a time that
892 appears one hour off. This happens due to a flaw in how Windows stores and
893 uses file modification times and it is not easily worked around. For details
894 on this problem, read this: http://www.codeproject.com/datetime/dstbugs.asp
896 4.14 Redirects work in browser but not with curl!
898 curl supports HTTP redirects fine (see item 3.8). Browsers generally support
899 at least two other ways to perform directs that curl does not:
901 - Meta tags. You can write a HTML tag that will cause the browser to
902 redirect to another given URL after a certain time.
904 - Javascript. You can write a Javascript program embedded in a HTML page
905 that redirects the browser to another given URL.
907 There is no way to make curl follow these redirects. You must either
908 manually figure out what the page is set to do, or you write a script that
909 parses the results and fetches the new URL.
911 4.15 FTPS doesn't work
913 curl supports FTPS (sometimes known as FTP-SSL) both implicit and explicit
916 When a URL is used that starts with FTPS://, curl assumes implicit SSL on
917 the control connection and will therefore immediately connect and try to
918 speak SSL. FTPS:// connections default to port 990.
920 To use explicit FTPS, you use a FTP:// URL and the --ftp-ssl option (or one
921 of its related flavours). This is the most common method, and the one
922 mandated by RFC4217. This kind of connection then of course uses the
923 standard FTP port 21 by default.
925 4.16 My HTTP POST or PUT requests are slow!
927 libcurl makes all POST and PUT requests (except for POST requests with a
928 very tiny request body) use the "Expect: 100-continue" header. This header
929 allows the server to deny the operation early so that libcurl can bail out
930 already before having to send any data. This is useful in authentication
933 However, many servers don't implement the Expect: stuff properly and if the
934 server doesn't respond (positively) within 1 second libcurl will continue
935 and send off the data anyway.
937 You can disable libcurl's use of the Expect: header the same way you disable
938 any header, using -H / CURLOPT_HTTPHEADER, or by forcing it to use HTTP 1.0.
940 4.17 Non-functional connect timeouts
942 In most Windows setups having a timeout longer than 21 seconds make no
943 difference, as it will only send 3 TCP SYN packets and no more. The second
944 packet sent three seconds after the first and the third six seconds after
945 the second. No more than three packets are sent, no matter how long the
948 See option TcpMaxConnectRetransmissions on this page:
949 http://support.microsoft.com/?scid=kb%3Ben-us%3B175523&x=6&y=7
951 Also, even on non-Windows systems there may run a firewall or anti-virus
952 software or similar that accepts the connection but does not actually do
953 anything else. This will make (lib)curl to consider the connection connected
954 and thus the connect timeout won't trigger.
956 4.18 file:// URLs containing drive letters (Windows, NetWare)
958 When using cURL to try to download a local file, one might use a URL
963 You'll find that even if D:\blah.txt does exist, cURL returns a 'file
966 According to RFC 1738 (http://www.faqs.org/rfcs/rfc1738.html),
967 file:// URLs must contain a host component, but it is ignored by
968 most implementations. In the above example, 'D:' is treated as the
969 host component, and is taken away. Thus, cURL tries to open '/blah.txt'.
970 If your system is installed to drive C:, that will resolve to 'C:\blah.txt',
971 and if that doesn't exist you will get the not found error.
973 To fix this problem, use file:// URLs with *three* leading slashes:
977 Alternatively, if it makes more sense, specify 'localhost' as the host
980 file://localhost/D:/blah.txt
982 In either case, cURL should now be looking for the correct file.
984 4.19 Why doesn't cURL return an error when the network cable is unplugged?
986 Unplugging the cable is not an error situation. The TCP/IP protocol stack
987 was designed to be fault tolerant, so even though there may be a physical
988 break somewhere the connection shouldn't be affected, just possibly
989 delayed. Eventually, the physical break will be fixed or the data will be
990 re-routed around the physical problem.
992 In such cases, the TCP/IP stack is responsible for detecting when the
993 network connection is irrevocably lost. Since with some protocols it is
994 perfectly legal for the client wait indefinitely for data, the stack may
995 never report a problem, and even when it does, it can take up to 20 minutes
996 for it to detect an issue. The curl option --keepalive-time enables
997 keep-alive support in the TCP/IP stack which makes it periodically probe the
998 connection to make sure it is still available to send data. That should
999 reliably detect any TCP/IP network failure.
1001 But even that won't detect the network going down before the TCP/IP
1002 connection is established (e.g. during a DNS lookup) or using protocols that
1003 don't use TCP. To handle those situations, curl offers a number of timeouts
1004 on its own. --speed-limit/--speed-time will abort if the data transfer rate
1005 falls too low, and --connect-timeout and --max-time can be used to put an
1006 overall timeout on the connection phase or the entire transfer.
1011 5.1 Is libcurl thread-safe?
1015 We have written the libcurl code specifically adjusted for multi-threaded
1016 programs. libcurl will use thread-safe functions instead of non-safe ones if
1017 your system has such.
1019 If you use a OpenSSL-powered libcurl in a multi-threaded environment, you
1020 need to provide one or two locking functions:
1022 http://www.openssl.org/docs/crypto/threads.html
1024 If you use a GnuTLS-powered libcurl in a multi-threaded environment, you
1025 need to provide locking function(s) for libgcrypt (which is used by GnuTLS
1026 for the crypto functions).
1028 http://www.gnu.org/software/gnutls/manual/html_node/Multi_002dthreaded-applications.html
1030 No special locking is needed with a NSS-powered libcurl. NSS is thread-safe.
1032 5.2 How can I receive all data into a large memory chunk?
1034 [ See also the examples/getinmemory.c source ]
1036 You are in full control of the callback function that gets called every time
1037 there is data received from the remote server. You can make that callback do
1038 whatever you want. You do not have to write the received data to a file.
1040 One solution to this problem could be to have a pointer to a struct that you
1041 pass to the callback function. You set the pointer using the
1042 CURLOPT_WRITEDATA option. Then that pointer will be passed to the callback
1043 instead of a FILE * to a file:
1045 /* imaginary struct */
1046 struct MemoryStruct {
1051 /* imaginary callback function */
1053 WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data)
1055 size_t realsize = size * nmemb;
1056 struct MemoryStruct *mem = (struct MemoryStruct *)data;
1058 mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1);
1060 memcpy(&(mem->memory[mem->size]), ptr, realsize);
1061 mem->size += realsize;
1062 mem->memory[mem->size] = 0;
1067 5.3 How do I fetch multiple files with libcurl?
1069 libcurl has excellent support for transferring multiple files. You should
1070 just repeatedly set new URLs with curl_easy_setopt() and then transfer it
1071 with curl_easy_perform(). The handle you get from curl_easy_init() is not
1072 only reusable, but you're even encouraged to reuse it if you can, as that
1073 will enable libcurl to use persistent connections.
1075 5.4 Does libcurl do Winsock initialization on win32 systems?
1077 Yes, if told to in the curl_global_init() call.
1079 5.5 Does CURLOPT_WRITEDATA and CURLOPT_READDATA work on win32 ?
1081 Yes, but you cannot open a FILE * and pass the pointer to a DLL and have
1082 that DLL use the FILE * (as the DLL and the client application cannot access
1083 each others' variable memory areas). If you set CURLOPT_WRITEDATA you must
1084 also use CURLOPT_WRITEFUNCTION as well to set a function that writes the
1085 file, even if that simply writes the data to the specified FILE *.
1086 Similarly, if you use CURLOPT_READDATA you must also specify
1087 CURLOPT_READFUNCTION.
1089 5.6 What about Keep-Alive or persistent connections?
1091 curl and libcurl have excellent support for persistent connections when
1092 transferring several files from the same server. Curl will attempt to reuse
1093 connections for all URLs specified on the same command line/config file, and
1094 libcurl will reuse connections for all transfers that are made using the
1095 same libcurl handle.
1097 5.7 Link errors when building libcurl on Windows!
1099 You need to make sure that your project, and all the libraries (both static
1100 and dynamic) that it links against, are compiled/linked against the same run
1103 This is determined by the /MD, /ML, /MT (and their corresponding /M?d)
1104 options to the command line compiler. /MD (linking against MSVCRT dll) seems
1105 to be the most commonly used option.
1107 When building an application that uses the static libcurl library, you must
1108 add -DCURL_STATICLIB to your CFLAGS. Otherwise the linker will look for
1109 dynamic import symbols. If you get linker error like "unknown symbol
1110 __imp__curl_easy_init ..." you have linked against the wrong (static)
1111 library. If you want to use the libcurl.dll and import lib, you don't need
1112 any extra CFLAGS, but use one of the import libraries below. These are the
1113 libraries produced by the various lib/Makefile.* files:
1115 Target: static lib. import lib for libcurl*.dll.
1116 -----------------------------------------------------------
1117 MingW: libcurl.a libcurldll.a
1118 MSVC (release): libcurl.lib libcurl_imp.lib
1119 MSVC (debug): libcurld.lib libcurld_imp.lib
1120 Borland: libcurl.lib libcurl_imp.lib
1123 5.8 libcurl.so.X: open failed: No such file or directory
1125 This is an error message you might get when you try to run a program linked
1126 with a shared version of libcurl and your run-time linker (ld.so) couldn't
1127 find the shared library named libcurl.so.X. (Where X is the number of the
1128 current libcurl ABI, typically 3 or 4).
1130 You need to make sure that ld.so finds libcurl.so.X. You can do that
1131 multiple ways, and it differs somewhat between different operating systems,
1132 but they are usually:
1134 * Add an option to the linker command line that specify the hard-coded path
1135 the run-time linker should check for the lib (usually -R)
1137 * Set an environment variable (LD_LIBRARY_PATH for example) where ld.so
1138 should check for libs
1140 * Adjust the system's config to check for libs in the directory where you've
1141 put the dir (like Linux's /etc/ld.so.conf)
1143 'man ld.so' and 'man ld' will tell you more details
1145 5.9 How does libcurl resolve host names?
1147 libcurl supports a large a number of different name resolve functions. One
1148 of them is picked at build-time and will be used unconditionally. Thus, if
1149 you want to change name resolver function you must rebuild libcurl and tell
1150 it to use a different function.
1152 - The non-ipv6 resolver that can use one out of four host name resolve calls
1153 (depending on what your system supports):
1156 B - gethostbyname_r() with 3 arguments
1157 C - gethostbyname_r() with 5 arguments
1158 D - gethostbyname_r() with 6 arguments
1160 - The ipv6-resolver that uses getaddrinfo()
1162 - The c-ares based name resolver that uses the c-ares library for resolves.
1163 Using this offers asynchronous name resolves but it currently has no IPv6
1166 - The threaded resolver (default option on Windows). It uses:
1168 A - gethostbyname() on plain ipv4 hosts
1169 B - getaddrinfo() on ipv6-enabled hosts
1171 Also note that libcurl never resolves or reverse-lookups addresses given as
1172 pure numbers, such as 127.0.0.1 or ::1.
1174 5.10 How do I prevent libcurl from writing the response to stdout?
1176 libcurl provides a default built-in write function that writes received data
1177 to stdout. Set the CURLOPT_WRITEFUNCTION to receive the data, or possibly
1178 set CURLOPT_WRITEDATA to a different FILE * handle.
1180 5.11 How do I make libcurl not receive the whole HTTP response?
1182 You make the write callback (or progress callback) return an error and
1183 libcurl will then abort the transfer.
1185 5.12 Can I make libcurl fake or hide my real IP address?
1187 No. libcurl operates on a higher level than so. Besides, faking IP address
1188 would imply sending IP packages with a made-up source address, and then you
1189 normally get a problem with intercepting the packages sent back as they
1190 would then not be routed to you!
1192 If you use a proxy to access remote sites, the sites will not see your local
1193 IP address but instead the address of the proxy.
1195 Also note that on many networks NATs or other IP-munging techniques are used
1196 that makes you see and use a different IP address locally than what the
1197 remote server will see you coming from.
1199 5.13 How do I stop an ongoing transfer?
1201 There are several ways, but none of them are instant. There is no function
1202 you can call from another thread or similar that will stop it immediately.
1203 Instead you need to make sure that one of the callbacks you use return an
1204 appropriate value that will stop the transfer.
1206 Suitable callbacks that you can do this with include the progress callback,
1207 the read callback and the write callback.
1209 If you're using the multi interface, you also stop a transfer by removing
1210 the particular easy handle from the multi stack.
1212 5.14 Using C++ non-static functions for callbacks?
1214 libcurl is a C library, it doesn't know anything about C++ member functions.
1216 You can overcome this "limitation" with a relative ease using a static
1217 member function that is passed a pointer to the class:
1219 // f is the pointer to your object.
1220 static YourClass::staticFunction(void *buffer, size_t sz, size_t n, void *f)
1222 // Call non-static member function.
1223 static_cast<YourClass*>(f)->nonStaticFunction();
1226 // This is how you pass pointer to the static function:
1227 curl_easy_setopt(hcurl, CURLOPT_WRITEFUNCTION, YourClass:staticFunction);
1228 curl_easy_setopt(hcurl, CURLOPT_WRITEDATA, this);
1230 5.15 How do I get an FTP directory listing?
1232 If you end the FTP URL you request with a slash, libcurl will provide you
1233 with a directory listing of that given directory. You can also set
1234 CURLOPT_CUSTOMREQUEST to alter what exact listing command libcurl would use
1237 The follow-up question that tend to follow the previous one, is how a
1238 program is supposed to parse the directory listing. How does it know what's
1239 a file and what's a dir and what's a symlink etc. The harsh reality is that
1240 FTP provides no such fine and easy-to-parse output. The output format FTP
1241 servers respond to LIST commands are entirely at the server's own liking and
1242 the NLST output doesn't reveal any types and in many cases don't even
1243 include all the directory entries. Also, both LIST and NLST tend to hide
1244 unix-style hidden files (those that start with a dot) by default so you need
1245 to do "LIST -a" or similar to see them.
1247 The application thus needs to parse the LIST output. One such existing
1248 list parser is available at http://cr.yp.to/ftpparse.html Versions of
1249 libcurl since 7.21.0 also provide the ability to specify a wildcard to
1250 download multiple files from one FTP directory.
1255 Curl and libcurl are released under a MIT/X derivate license. The license is
1256 very liberal and should not impose a problem for your project. This section
1257 is just a brief summary for the cases we get the most questions. (Parts of
1258 this section was much enhanced by Bjorn Reese.)
1260 We are not lawyers and this is not legal advice. You should probably consult
1261 one if you want true and accurate legal insights without our prejudice.
1263 6.1 I have a GPL program, can I use the libcurl library?
1267 Since libcurl may be distributed under the MIT/X derivate license, it can be
1268 used together with GPL in any software.
1270 6.2 I have a closed-source program, can I use the libcurl library?
1274 libcurl does not put any restrictions on the program that uses the library.
1276 6.3 I have a BSD licensed program, can I use the libcurl library?
1280 libcurl does not put any restrictions on the program that uses the library.
1282 6.4 I have a program that uses LGPL libraries, can I use libcurl?
1286 The LGPL license doesn't clash with other licenses.
1288 6.5 Can I modify curl/libcurl for my program and keep the changes secret?
1292 The MIT/X derivate license practically allows you to do almost anything with
1293 the sources, on the condition that the copyright texts in the sources are
1296 6.6 Can you please change the curl/libcurl license to XXXX?
1300 We have carefully picked this license after years of development and
1301 discussions and a large amount of people have contributed with source code
1302 knowing that this is the license we use. This license puts the restrictions
1303 we want on curl/libcurl and it does not spread to other programs or
1304 libraries that use it. It should be possible for everyone to use libcurl or
1305 curl in their projects, no matter what license they already have in use.
1307 6.7 What are my obligations when using libcurl in my commercial apps?
1309 Next to none. All you need to adhere to is the MIT-style license (stated in
1310 the COPYING file) which basically says you have to include the copyright
1311 notice in "all copies" and that you may not use the copyright holder's name
1312 when promoting your software.
1314 You do not have to release any of your source code.
1316 You do not have to reveal or make public any changes to the libcurl source
1319 You do not have to reveal or make public that you are using libcurl within
1322 As can be seen here: http://curl.haxx.se/docs/companies.html and
1323 elsewhere, more and more companies are discovering the power
1324 of libcurl and take advantage of it even in commercial environments.
1329 7.1 What is PHP/CURL?
1331 The module for PHP that makes it possible for PHP programs to access curl-
1332 functions from within PHP.
1334 In the cURL project we call this module PHP/CURL to differentiate it from
1335 curl the command line tool and libcurl the library. The PHP team however
1336 does not refer to it like this (for unknown reasons). They call it plain
1337 CURL (often using all caps) or sometimes ext/curl, but both cause much
1338 confusion to users which in turn gives us a higher question load.
1340 7.2 Who write PHP/CURL?
1342 PHP/CURL is a module that comes with the regular PHP package. It depends and
1343 uses libcurl, so you need to have libcurl installed properly first before
1344 PHP/CURL can be used. PHP/CURL was initially written by Sterling Hughes.
1346 7.3 Can I perform multiple requests using the same handle?
1348 Yes - at least in PHP version 4.3.8 and later (this has been known to not
1349 work in earlier versions, but the exact version when it started to work is
1352 After a transfer, you just set new options in the handle and make another
1353 transfer. This will make libcurl to re-use the same connection if it can.