| Updated: March 11, 2002 (http://curl.haxx.se/docs/faq.shtml) |
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| | (__| |_| | _ <| |___ |
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| |
| FAQ |
| |
| 1. Philosophy |
| 1.1 What is cURL? |
| 1.2 What is libcurl? |
| 1.3 What is cURL not? |
| 1.4 When will you make curl do XXXX ? |
| 1.5 Who makes cURL? |
| 1.6 What do you get for making cURL? |
| 1.7 What about CURL from curl.com? |
| |
| 2. Install Related Problems |
| 2.1 configure doesn't find OpenSSL even when it is installed |
| 2.1.1. native linker doesn't find openssl |
| 2.1.2. only the libssl lib is missing |
| 2.2 Does curl work/build with other SSL libraries? |
| 2.3 Where can I find a copy of LIBEAY32.DLL? |
| 2.4 Does cURL support Socks (RFC 1928) ? |
| |
| 3. Usage Problems |
| 3.1 curl: (1) SSL is disabled, https: not supported |
| 3.2 How do I tell curl to resume a transfer? |
| 3.3 Why doesn't my posting using -F work? |
| 3.4 How do I tell curl to run custom FTP commands? |
| 3.5 How can I disable the Pragma: nocache header? |
| 3.6 Does curl support javascript, ASP, XML, XHTML or HTML version Y? |
| 3.7 Can I use curl to delete/rename a file through FTP? |
| 3.8 How do I tell curl to follow HTTP redirects? |
| 3.9 How do I use curl in my favourite programming language? |
| 3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP? |
| 3.11 How do I POST with a different Content-Type? |
| 3.12 Why do FTP specific features over HTTP proxy fail? |
| 3.13 Why does my single/double quotes fail? |
| |
| 4. Running Problems |
| 4.1 Problems connecting to SSL servers. |
| 4.2 Why do I get problems when I use & or % in the URL? |
| 4.3 How can I use {, }, [ or ] to specify multiple URLs? |
| 4.4 Why do I get downloaded data even though the web page doesn't exist? |
| 4.5 Why do I get return code XXX from a HTTP server? |
| 4.5.1 "400 Bad Request" |
| 4.5.2 "401 Unauthorized" |
| 4.5.3 "403 Forbidden" |
| 4.5.4 "404 Not Found" |
| 4.5.5 "405 Method Not Allowed" |
| 4.5.6 "301 Moved Permanently" |
| 4.6 Can you tell me what error code 142 means? |
| 4.7 How do I keep user names and passwords secret in Curl command lines? |
| 4.8 I found a bug! |
| 4.9 Curl can't authenticate to the server that requires NTLM? |
| |
| 5. libcurl Issues |
| 5.1 Is libcurl thread-safe? |
| 5.2 How can I receive all data into a large memory chunk? |
| 5.3 How do I fetch multiple files with libcurl? |
| 5.4 Does libcurl do Winsock initing on win32 systems? |
| 5.5 Does CURLOPT_FILE and CURLOPT_INFILE work on win32 ? |
| 5.6 What about Keep-Alive or persistent connections? |
| |
| 6. License Issues |
| 6.1 I have a GPL program, can I use the libcurl library? |
| 6.2 I have a closed-source program, can I use the libcurl library? |
| 6.3 I have a BSD licensed program, can I use the libcurl library? |
| 6.4 I have a program that uses LGPL libraries, can I use libcurl? |
| 6.5 Can I modify curl/libcurl for my program and keep the changes secret? |
| 6.6 Can you please change the curl/libcurl license to XXXX? |
| |
| ============================================================================== |
| |
| 1. Philosophy |
| |
| 1.1 What is cURL? |
| |
| cURL (or simply just 'curl') is a command line tool for getting or sending |
| files using URL syntax. The name is a play on 'Client for URLs', originally |
| with URL spelled in uppercase to make it obvious it deals with URLs. The |
| fact it can also be pronounced 'see URL' also helped. |
| |
| Curl supports a range of common Internet protocols, currently including |
| HTTP, HTTPS, FTP, FTPS, GOPHER, LDAP, DICT, TELNET and FILE. |
| |
| We spell it cURL or just curl. We pronounce it with an initial k sound: |
| [kurl]. |
| |
| 1.2 What is libcurl? |
| |
| libcurl is a reliable and portable library which provides you with an easy |
| interface to a range of common Internet protocols. |
| |
| You can use libcurl for free in your application even if it is commercial |
| or closed-source. |
| |
| 1.3 What is cURL not? |
| |
| Curl is *not* a wget clone even though that is a very common misconception. |
| Never, during curl's development, have we intended curl to replace wget or |
| compete on its market. Curl is targeted at single-shot file transfers. |
| |
| Curl is not a web site mirroring program. If you wanna use curl to mirror |
| something: fine, go ahead and write a script that wraps around curl to make |
| it reality (like curlmirror.pl does). |
| |
| Curl is not an FTP site mirroring program. Sure, get and send FTP with curl |
| but if you want systematic and sequential behavior you should write a |
| script (or write a new program that interfaces libcurl) and do it. |
| |
| Curl is not a PHP tool, even though it works perfectly well when used from |
| or with PHP. |
| |
| Curl is not a single-OS program. Curl exists, compiles, builds and runs |
| under a wide range of operating systems, including all modern Unixes (and a |
| bunch of older ones too), Windows, Amiga, BeOS, OS/2, OS X, QNX etc. |
| |
| 1.4 When will you make curl do XXXX ? |
| |
| We love suggestions of what to change in order to make curl and libcurl |
| better. We do however believe in a few rules when it comes to the future of |
| curl: |
| |
| * Curl is to remain a command line tool. If you want GUIs or fancy scripting |
| capabilities, you're free to write another tool that uses libcurl and that |
| offers this. There's no point in having a single tool that does every |
| imaginable thing. That's also one of the great advantages of having the |
| core of curl as a library. |
| |
| * We do not add things to curl that other small and available tools already |
| do very fine at the side. Curl's output is fine to pipe into another |
| program or redirect to another file for the next program to interpret. |
| |
| * We focus on protocol related issues and improvements. If you wanna do more |
| magic with the supported protocols than curl currently does, chances are |
| big we will agree. If you wanna add more protocols, we may very well |
| agree. |
| |
| * If you want someone else to make all the work while you wait for us to |
| implement it for you, that is not a very friendly attitude. We spend a |
| considerable time already on maintaining and developing curl. In order to |
| get more out of us, you should consider trading in some of your time and |
| efforts in return. |
| |
| * If you write the code, chances are bigger that it will get into curl |
| faster. |
| |
| 1.5 Who makes cURL? |
| |
| cURL and libcurl are not made by any single individual. Sure, Daniel |
| Stenberg writes the major parts, but various people's submissions are |
| important and crucial. Anyone can post their changes and improvements and |
| have them inserted in the main sources (of course on the condition that |
| developers agree on that the fixes are good). |
| |
| The list of contributors in the docs/THANKS file is only a small part of all |
| the people that every day provide us with bug reports, suggestions, ideas |
| and source code. |
| |
| curl is developed by a community, with Daniel at the wheel. |
| |
| 1.6 What do you get for making cURL? |
| |
| Project cURL is entirely free and open. No person gets paid in any way for |
| developing curl. We all do this voluntarily on our spare time. |
| |
| We get some help from companies. Contactor Data hosts the curl web site and |
| the main mailing list, Haxx owns the curl web site's domain and |
| sourceforge.net hosts several project tools we take advantage from like the |
| bug tracker, mailing lists and more. |
| |
| If you want to support our project with a donation or similar, one way of |
| doing that would be to buy "gift certificates" at useful online shopping |
| sites, such as amazon.com or thinkgeek.com. Another way would be to sponsor |
| us through a banner-program or by simply helping us coding, documenting, |
| testing etc. |
| |
| 1.7 What about CURL from curl.com? |
| |
| During the summer 2001, curl.com has been busy advertising their client-side |
| programming language for the web, named CURL. |
| |
| We are in no way associated with curl.com or their CURL programming |
| language. |
| |
| Our project name curl has been in effective use since 1998. We were not the |
| first computer related project to use the name "curl" and do not claim any |
| first-hand rights to the name. |
| |
| We recognize that we will be living in parallel with curl.com and wish them |
| every success. |
| |
| 2. Install Related Problems |
| |
| 2.1. configure doesn't find OpenSSL even when it is installed |
| |
| This may be because of several reasons. |
| |
| 2.1.1. native linker doesn't find openssl |
| |
| Affected platforms: |
| Solaris (native cc compiler) |
| HPUX (native cc compiler) |
| SGI IRIX (native cc compiler) |
| SCO UNIX (native cc compiler) |
| |
| When configuring curl, I specify --with-ssl. OpenSSL is installed in |
| /usr/local/ssl Configure reports SSL in /usr/local/ssl, but fails to find |
| CRYPTO_lock in -lcrypto |
| |
| Cause: The cc for this test places the -L/usr/local/ssl/lib AFTER |
| -lcrypto, so ld can't find the library. This is due to a bug in the GNU |
| autoconf tool. |
| |
| Workaround: Specifying "LDFLAGS=-L/usr/local/ssl/lib" in front of |
| ./configure places the -L/usr/local/ssl/lib early enough in the command |
| line to make things work |
| |
| Solution submitted by: Bob Allison <allisonb@users.sourceforge.net> |
| |
| 2.1.2. only the libssl lib is missing |
| |
| If all include files and the libcrypto lib is present, with only the |
| libssl being missing according to configure, this is mostly likely because |
| a few functions are left out from the libssl. |
| |
| If the function names missing include RSA or RSAREF you can be certain |
| that this is because libssl requires the RSA and RSAREF libs to build. |
| |
| See the INSTALL file section that explains how to add those libs to |
| configure. Make sure that you remove the config.cache file before you |
| rerun configure with the new flags. |
| |
| 2.2. Does curl work/build with other SSL libraries? |
| |
| Curl has been written to use OpenSSL, although there should not be much |
| problems using a different library. If anyone does "port" curl to use a |
| different SSL library, we are of course very interested in getting the |
| patch! |
| |
| 2.3. Where can I find a copy of LIBEAY32.DLL? |
| |
| That is an OpenSSL binary built for Windows. |
| |
| Curl uses OpenSSL to do the SSL stuff. The LIBEAY32.DLL is what curl needs |
| on a windows machine to do https://. Check out the curl web site to find |
| accurate and up-to-date pointers to recent OpenSSL DLLs and other binary |
| packages. |
| |
| 2.4. Does cURL support Socks (RFC 1928) ? |
| |
| No. Nobody has wanted it that badly yet. We appreciate patches that bring |
| this functionality. |
| |
| |
| 3. Usage problems |
| |
| 3.1. curl: (1) SSL is disabled, https: not supported |
| |
| If you get this output when trying to get anything from a https:// server, |
| it means that the configure script couldn't find all libs and include files |
| it requires for SSL to work. If the configure script fails to find them, |
| curl is simply built without SSL support. |
| |
| To get the https:// support into a curl that was previously built but that |
| reports that https:// is not supported, you should dig through the document |
| and logs and check out why the configure script doesn't find the SSL libs |
| and/or include files. |
| |
| Also, check out the other paragraph in this FAQ labeled "configure doesn't |
| find OpenSSL even when it is installed". |
| |
| 3.2. How do I tell curl to resume a transfer? |
| |
| Curl supports resumed transfers both ways on both FTP and HTTP. |
| |
| Try the -C option. |
| |
| 3.3. Why doesn't my posting using -F work? |
| |
| You can't simply use -F or -d at your choice. The web server that will |
| receive your post assumes one of the formats. If the form you're trying to |
| "fake" sets the type to 'multipart/form-data', then and only then you must |
| use the -F type. In all the most common cases, you should use -d which then |
| causes a posting with the type 'application/x-www-form-urlencoded'. |
| |
| This is described in some detail in the MANUAL and TheArtOfHttpScripting |
| documents, and if you don't understand it the first time, read it again |
| before you post questions about this to the mailing list. Also, try reading |
| through the mailing list archives for old postings and questions regarding |
| this. |
| |
| 3.4. How do I tell curl to run custom FTP commands? |
| |
| You can tell curl to perform optional commands both before and/or after a |
| file transfer. Study the -Q/--quote option. |
| |
| Since curl is used for file transfers, you don't use curl to just perform |
| FTP commands without transferring anything. Therefore you must always specify |
| a URL to transfer to/from even when doing custom FTP commands. |
| |
| 3.5. How can I disable the Pragma: nocache header? |
| |
| You can change all internally generated headers by adding a replacement with |
| the -H/--header option. By adding a header with empty contents you safely |
| disable that one. Use -H "Pragma:" to disable that specific header. |
| |
| 3.6. Does curl support javascript, ASP, XML, XHTML or HTML version Y? |
| |
| To curl, all contents are alike. It doesn't matter how the page was |
| generated. It may be ASP, PHP, Perl, shell-script, SSI or plain |
| HTML-files. There's no difference to curl and it doesn't even know what kind |
| of language that generated the page. |
| |
| Javascript is slightly different since that is code embedded in the HTML |
| that is sent for the client to interpret and curl has no javascript |
| interpreter. |
| |
| 3.7. Can I use curl to delete/rename a file through FTP? |
| |
| Yes. You specify custom FTP commands with -Q/--quote. |
| |
| One example would be to delete a file after you have downloaded it: |
| |
| curl -O ftp://download.com/coolfile -Q '-DELE coolfile' |
| |
| 3.8 How do I tell curl to follow HTTP redirects? |
| |
| Curl does not follow so-called redirects by default. The Location: header |
| that informs the client about this is only interpreted if you're using the |
| -L/--location option. As in: |
| |
| curl -L http://redirector.com |
| |
| 3.9 How do I use curl in my favourite programming language? |
| |
| There exist many language interfaces/bindings for curl that integrates it |
| better with various languages. If you are fluid in a script language, you |
| may very well opt to use such an interface instead of using the command line |
| tool. |
| |
| Find out more about which languages that support curl directly, and how to |
| install and use them, in the libcurl section of the curl web site: |
| |
| http://curl.haxx.se/libcurl/ |
| |
| In December 2001, there are interfaces available for the following |
| languages: C/C++, Cocoa, Dylan, Java, Perl, PHP, Python, Rexx, Ruby, Scheme |
| and Tcl. By the time you read this, additional ones may have appeared! |
| |
| 3.10 What about SOAP, WebDAV, XML-RPC or similar protocols over HTTP? |
| |
| Curl adheres to the HTTP spec, which basically means you can play with *any* |
| protocol that is built on top of HTTP. Protocols such as SOAP, WEBDAV and |
| XML-RPC are all such ones. You can use -X to set custom requests and -H to |
| set custom headers (or replace internally generated ones). |
| |
| Using libcurl or PHP's curl modules is just as fine and you'd just use the |
| proper library options to do the same. |
| |
| 3.11 How do I POST with a different Content-Type? |
| |
| You can always replace the internally generated headers with -H/--header. |
| To make a simple HTTP POST with text/xml as content-type, do something like: |
| |
| curl -d "datatopost" -H "Content-Type: text/xml" [URL] |
| |
| 3.12 Why do FTP specific features over HTTP proxy fail? |
| |
| Because when you use a HTTP proxy, the protocol spoken on the network will |
| be HTTP, even if you specify a FTP URL. This effectively means that you |
| normally can't use FTP specific features such as ftp upload and ftp quote |
| etc. |
| |
| There is one exception to this rule, and that is if you can "tunnel through" |
| the given HTTP proxy. Proxy tunneling is enabled with a special option (-p) |
| and is generally not available as proxy admins usually disable tunneling to |
| other ports than 443 (which is used for HTTPS access through proxies). |
| |
| 3.13 Why does my single/double quotes fail? |
| |
| To specify a command line option that includes spaces, you might need to |
| put the entire option within quotes. Like in: |
| |
| curl -d " with spaces " url.com |
| |
| or perhaps |
| |
| curl -d ' with spaces ' url.com |
| |
| Exactly what kind of quotes and how to do this is entirely up to the shell |
| or command line interepreter that you are using. For most unix shells, you |
| can more or less pick either single (') or double (") quotes. For |
| Windows/DOS prompts I believe you're forced to use double (") quotes. |
| |
| Please study the documentaion for your particular environment. Examples in |
| the curl docs will use a mix of both these ones as shown above. You must |
| adjust them to work in your environment. |
| |
| Remember that curl works and runs on more operating systems than most single |
| individuals have ever tried. |
| |
| |
| 4. Running Problems |
| |
| 4.1. Problems connecting to SSL servers. |
| |
| It took a very long time before we could sort out why curl had problems to |
| connect to certain SSL servers when using SSLeay or OpenSSL v0.9+. The |
| error sometimes showed up similar to: |
| |
| 16570:error:1407D071:SSL routines:SSL2_READ:bad mac decode:s2_pkt.c:233: |
| |
| It turned out to be because many older SSL servers don't deal with SSLv3 |
| requests properly. To correct this problem, tell curl to select SSLv2 from |
| the command line (-2/--sslv2). |
| |
| There has also been examples where the remote server didn't like the SSLv2 |
| request and instead you had to force curl to use SSLv3 with -3/--sslv3. |
| |
| 4.2. Why do I get problems when I use & or % in the URL? |
| |
| In general unix shells, the & letter is treated special and when used, it |
| runs the specified command in the background. To safely send the & as a part |
| of a URL, you should quote the entire URL by using single (') or double (") |
| quotes around it. |
| |
| An example that would invoke a remote CGI that uses &-letters could be: |
| |
| curl 'http://www.altavista.com/cgi-bin/query?text=yes&q=curl' |
| |
| In win32, the standard DOS shell treats the %-letter specially and you may |
| need to quote the string properly when % is used in it. |
| |
| Also note that if you want the literal %-letter to be part of the data you |
| pass in a POST using -d/--data you must encode it as '%25'. |
| |
| 4.3. How can I use {, }, [ or ] to specify multiple URLs? |
| |
| Because those letters have a special meaning to the shell, and to be used in |
| a URL specified to curl you must quote them. |
| |
| An example that downloads two URLs (sequentially) would do: |
| |
| curl '{curl,www}.haxx.se' |
| |
| To be able to use those letters as actual parts of the URL (without using |
| them for the curl URL "globbing" system), use the -g/--globoff option (curl |
| 7.6 and later): |
| |
| curl -g 'www.site.com/weirdname[].html' |
| |
| 4.4. Why do I get downloaded data even though the web page doesn't exist? |
| |
| Curl asks remote servers for the page you specify. If the page doesn't exist |
| at the server, the HTTP protocol defines how the server should respond and |
| that means that headers and a "page" will be returned. That's simply how |
| HTTP works. |
| |
| By using the --fail option you can tell curl explicitly to not get any data |
| if the HTTP return code doesn't say success. |
| |
| 4.5 Why do I get return code XXX from a HTTP server? |
| |
| RFC2616 clearly explains the return codes. This is a short transcript. Go |
| read the RFC for exact details: |
| |
| 4.5.1 "400 Bad Request" |
| |
| The request could not be understood by the server due to malformed |
| syntax. The client SHOULD NOT repeat the request without modifications. |
| |
| 4.5.2 "401 Unauthorized" |
| |
| The request requires user authentication. |
| |
| 4.5.3 "403 Forbidden" |
| |
| The server understood the request, but is refusing to fulfill it. |
| Authorization will not help and the request SHOULD NOT be repeated. |
| |
| 4.5.4 "404 Not Found" |
| |
| The server has not found anything matching the Request-URI. No indication |
| is given of whether the condition is temporary or permanent. |
| |
| 4.5.5 "405 Method Not Allowed" |
| |
| The method specified in the Request-Line is not allowed for the resource |
| identified by the Request-URI. The response MUST include an Allow header |
| containing a list of valid methods for the requested resource. |
| |
| 4.5.6 "301 Moved Permanently" |
| |
| If you get this return code and an HTML outpt similar to this: |
| |
| <H1>Moved Permanently</H1> The document has moved <A |
| HREF="http://same_url_now_with_a_trailing_slash/">here</A>. |
| |
| it might be because you request a directory URL but without the trailing |
| slash. Try the same operation again _with_ the trailing URL, or use the |
| -L/--location option to follow the redirection. |
| |
| 4.6. Can you tell me what error code 142 means? |
| |
| All error codes that are larger than the highest documented error code means |
| that curl has exited due to a crash. This is a serious error, and we |
| appreciate a detailed bug report from you that describes how we could go |
| ahead and repeat this! |
| |
| 4.7. How do I keep user names and passwords secret in Curl command lines? |
| |
| This problem has two sides: |
| |
| The first part is to avoid having clear-text passwords in the command line |
| so that they don't appear in 'ps' outputs and similar. That is easily |
| avoided by using the "-K" option to tell curl to read parameters from a |
| file or stdin to which you can pass the secret info. |
| |
| To keep the passwords in your account secret from the rest of the world is |
| not a task that curl addresses. You could of course encrypt them somehow to |
| at least hide them from being read by human eyes, but that is not what |
| anyone would call security. |
| |
| Also note that regular HTTP and FTP passwords are sent in clear across the |
| network. All it takes for anyone to fetch them is to listen on the network. |
| Eavesdropping is very easy. |
| |
| 4.8 I found a bug! |
| |
| It is not a bug if the behavior is documented. Read the docs first. |
| |
| If it is a problem with a binary you've downloaded or a package for your |
| particular platform, try contacting the person who built the package/archive |
| you have. |
| |
| If there is a bug, post a bug report in the Curl Bug Track System over at |
| http://sourceforge.net/bugs/?group_id=976 |
| |
| Always include as many details you can think of, including curl version, |
| operating system name and version and complete instructions how to repeat |
| the bug. |
| |
| 4.9. Curl can't authenticate to the server that requires NTLM? |
| |
| NTLM is a Microsoft proprietary protocol. Unfortunately, curl does not |
| currently support that. Proprietary formats are evil. You should not use |
| such ones. |
| |
| 5. libcurl Issues |
| |
| 5.1. Is libcurl thread-safe? |
| |
| Yes. |
| |
| We have written the libcurl code specificly adjusted for multi-threaded |
| programs. libcurl will use thread-safe functions instead of non-safe ones if |
| your system has such. |
| |
| We would appreciate some kind of report or README file from those who have |
| used libcurl in a threaded environment. |
| |
| 5.2 How can I receive all data into a large memory chunk? |
| |
| [ See also the examples/getinmemory.c source ] |
| |
| You are in full control of the callback function that gets called every time |
| there is data received from the remote server. You can make that callback do |
| whatever you want. You do not have to write the received data to a file. |
| |
| One solution to this problem could be to have a pointer to a struct that you |
| pass to the callback function. You set the pointer using the |
| curl_easy_setopt(CURLOPT_FILE) function. Then that pointer will be passed to |
| the callback instead of a FILE * to a file: |
| |
| /* imaginary struct */ |
| struct MemoryStruct { |
| char *memory; |
| size_t size; |
| }; |
| |
| /* imaginary callback function */ |
| size_t |
| WriteMemoryCallback(void *ptr, size_t size, size_t nmemb, void *data) |
| { |
| register int realsize = size * nmemb; |
| struct MemoryStruct *mem = (struct MemoryStruct *)data; |
| |
| mem->memory = (char *)realloc(mem->memory, mem->size + realsize + 1); |
| if (mem->memory) { |
| memcpy(&(mem->memory[mem->size]), ptr, realsize); |
| mem->size += realsize; |
| mem->memory[mem->size] = 0; |
| } |
| return realsize; |
| } |
| |
| 5.3 How do I fetch multiple files with libcurl? |
| |
| Starting with version 7.7, curl and libcurl will have excellent support for |
| transferring multiple files. You should just repeatedly set new URLs with |
| curl_easy_setopt() and then transfer it with curl_easy_perform(). The handle |
| you get from curl_easy_init() is not only reusable starting with libcurl |
| 7.7, but also you're encouraged to reuse it if you can, as that will enable |
| libcurl to use persistent connections. |
| |
| For libcurl prior to 7.7, there was no multiple file support. The only |
| available way to do multiple requests was to init/perform/cleanup for each |
| transfer. |
| |
| 5.4 Does libcurl do Winsock initialization on win32 systems? |
| |
| Yes (since 7.8.1) if told to in the curl_global_init() call. |
| |
| 5.5 Does CURLOPT_FILE and CURLOPT_INFILE work on win32 ? |
| |
| Yes, but you cannot open a FILE * and pass the pointer to a DLL and have |
| that DLL use the FILE *. If you set CURLOPT_FILE you must also use |
| CURLOPT_WRITEFUNCTION as well to set a function that writes the file, even |
| if that simply writes the data to the specified FILE*. Similarly, if you use |
| CURLOPT_INFILE you must also specify CURLOPT_READFUNCTION. |
| |
| (Provided by Joel DeYoung and Bob Schader) |
| |
| 5.6 What about Keep-Alive or persistent connections? |
| |
| Starting with version 7.7, curl and libcurl will have excellent support for |
| persistent connections when transferring several files from the same server. |
| Curl will attempt to reuse connections for all URLs specified on the same |
| command line/config file, and libcurl will reuse connections for all |
| transfers that are made using the same libcurl handle. |
| |
| Previous versions had no persistent connection support. |
| |
| 6. License Issues |
| |
| Curl and libcurl are released under a MIT/X derivate license *or* the MPL, |
| the Mozilla Public License. To get a really good answer to your license |
| conflict questions, you should study the MPL and MIT/X licenses and the |
| license you are about to use and check for clashes yourself. This section is |
| just a brief summary for the cases we get the most questions. (Parts of this |
| section was much enhanced by Bjorn Reese.) |
| |
| 6.1. I have a GPL program, can I use the libcurl library? |
| |
| Yes! |
| |
| Since libcurl may be distributed under the MIT/X derivate license, it can be |
| used together with GPL in any software. |
| |
| 6.2. I have a closed-source program, can I use the libcurl library? |
| |
| Yes! |
| |
| libcurl does not put any restrictions on the program that uses the library. |
| |
| 6.3. I have a BSD licensed program, can I use the libcurl library? |
| |
| Yes! |
| |
| libcurl does not put any restrictions on the program that uses the library. |
| |
| 6.4. I have a program that uses LGPL libraries, can I use libcurl? |
| |
| Yes! |
| |
| The LGPL license doesn't clash with other licenses. |
| |
| 6.5. Can I modify curl/libcurl for my program and keep the changes secret? |
| |
| Yes! |
| |
| The MIT/X derivate license practically allows you to do almost anything with |
| the sources, on the condition that the copyright texts in the sources are |
| left intact. |
| |
| 6.6. Can you please change the curl/libcurl license to XXXX? |
| |
| No. |
| |
| We have carefully picked this license after years of development and |
| discussions and a large amount of people have contributed with source code |
| knowing that this is the license we use. This license puts the restrictions |
| we want on curl/libcurl and it does not spread to other programs or |
| libraries that use it. The recent dual license modification should make it |
| possible for everyone to use libcurl or curl in their projects, no matter |
| what license they already have in use. |