curl_easy_setopt(3)

NAME
curl_easy_setopt - set options for a curl easy handle

SYNOPSIS
#include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter);

DESCRIPTION
curl_easy_setopt() is used to tell libcurl how to behave. By using the appropriate options to curl_easy_setopt, you can change libcurl's behavior. All options are set with the option followed by a parameter. That parameter can be a long, a function pointer or an object pointer, all depending on what the specific option expects. Read this manual carefully as bad input values may cause libcurl to behave badly! You can only set one option in each function call. A typical application uses many curl_easy_setopt() calls in the setup phase. NOTE: strings passed to libcurl as 'char *' arguments, will not be copied by the library. Instead you should keep them available until libcurl no longer needs them. Failing to do so will cause very odd behavior or even crashes. libcurl will need them until you call curl_easy_cleanup() or you set the same option again to use a different pointer. NOTE2: options set with this function call are valid for the forthcoming data transfers that are performed when you invoke curl_easy_perform. The options are not in any way reset between transfers, so if you want subsequent transfers with different options, you must change them between the transfers. The handle is the return code from a curl_easy_init(3) or curl_easy_duphandle(3) call.

BEHAVIOR OPTIONS

CURLOPT_VERBOSE
    Set the parameter to non-zero to get the library to display a lot of verbose information about its operations. Very useful for libcurl and/or protocol debugging and understanding. You hardly ever want this set in production use, you will almost always want this when you debug/report problems. Another neat option for debugging is the CURLOPT_DEBUGFUNCTION.

CURLOPT_HEADER
    A non-zero parameter tells the library to include the header in the body output. This is only relevant for protocols that actually have headers preceding the data (like HTTP).

CURLOPT_NOPROGRESS
    A non-zero parameter tells the library to shut of the built-in progress meter completely. NOTE: future versions of libcurl is likely to not have any built-in progress meter at all.

CURLOPT_NOSIGNAL
    Pass a long. If it is non-zero, libcurl will not use any functions that install signal handlers or any functions that cause signals to be sent to the process. This option is mainly here to allow multi-threaded unix applications to still set/use all timeout options etc, without risking getting signals. (Added in 7.10)

CALLBACK OPTIONS

CURLOPT_WRITEFUNCTION
    Function pointer that should match the following prototype: size_t function( void *ptr, size_t size, size_t nmemb, void *stream); This function gets called by libcurl as soon as there is data reveiced that needs to be saved. The size of the data pointed to by ptr is size multiplied with nmemb, it will not be zero terminated. Return the number of bytes actually taken care of. If that amount differs from the amount passed to your function, it'll signal an error to the library and it will abort the transfer and return CURLE_WRITE_ERROR. Set the stream argument with the CURLOPT_FILE option. NOTE: you will be passed as much data as possible in all invokes, but you cannot possibly make any assumptions. It may be one byte, it may be thousands. The maximum amount of data that can be passed to the write callback is defined in the curl.h header file: CURL_MAX_WRITE_SIZE.

CURLOPT_WRITEDATA
    Data pointer to pass to the file write function. Note that if you specify the CURLOPT_WRITEFUNCTION, this is the pointer you'll get as input. If you don't use a callback, you must pass a 'FILE *' as libcurl will pass this to fwrite() when writing data. NOTE: If you're using libcurl as a win32 DLL, you MUST use the CURLOPT_WRITEFUNCTION if you set this option or you will experience crashes. This option is also known with the older name CURLOPT_FILE, the name CURLOPT_WRITEDATA was introduced in 7.9.7.

CURLOPT_READFUNCTION
    Function pointer that should match the following prototype: size_t function( void *ptr, size_t size, size_t nmemb, void *stream); This function gets called by libcurl as soon as it needs to read data in order to send it to the peer. The data area pointed at by the pointer ptr may be filled with at most size multiplied with nmemb number of bytes. Your function must return the actual number of bytes that you stored in that memory area. Returning 0 will signal end-of-file to the library and cause it to stop the current transfer.

CURLOPT_READDATA
    Data pointer to pass to the file read function. Note that if you specify the CURLOPT_READFUNCTION, this is the pointer you'll get as input. If you don't specify a read callback, this must be a valid FILE *. NOTE: If you're using libcurl as a win32 DLL, you MUST use a CURLOPT_READFUNCTION if you set this option. This option is also known with the older name CURLOPT_INFILE, the name CURLOPT_READDATA was introduced in 7.9.7.

CURLOPT_PROGRESSFUNCTION
    Function pointer that should match the curl_progress_callback prototype found in <curl/curl.h>. This function gets called by libcurl instead of its internal equivalent with a frequent interval during data transfer. Unknown/unused argument values will be set to zero (like if you only download data, the upload size will remain 0). Returning a non-zero value from this callback will cause libcurl to abort the transfer and return CURLE_ABORTED_BY_CALLBACK. Also note that CURLOPT_NOPROGRESS must be set to FALSE to make this function actually get called.

CURLOPT_PROGRESSDATA
    Pass a pointer that will be untouched by libcurl and passed as the first argument in the progress callback set with CURLOPT_PROGRESSFUNCTION.

CURLOPT_PASSWDFUNCTION
    Pass a pointer to a curl_passwd_callback function that will be called instead of the internal one if libcurl requests a password. The function must match this prototype: int getpass(void *client, char *prompt, char* buffer, int buflen );. If set to NULL, it sets back the function to the internal default one. If the function returns a non-zero value, it will abort the operation and an error (CURLE_BAD_PASSWORD_ENTERED) will be returned. client is a generic pointer, see CURLOPT_PASSWDDATA. prompt is a zero-terminated string that is text that prefixes the input request. buffer is a pointer to data where the entered password should be stored and buflen is the maximum number of bytes that may be written in the buffer. (Added in 7.4.2)

CURLOPT_PASSWDDATA
    Pass a void * to whatever data you want. The passed pointer will be the first argument sent to the specifed CURLOPT_PASSWDFUNCTION function. (Added in 7.4.2)

CURLOPT_HEADERFUNCTION
    Function pointer that should match the following prototype: size_t function( void *ptr, size_t size, size_t nmemb, void *stream);. This function gets called by libcurl as soon as there is received header data that needs to be written down. The headers are guaranteed to be written one-by-one and only complete lines are written. Parsing headers should be easy enough using this. The size of the data pointed to by ptr is size multiplied with nmemb. The pointer named stream will be the one you passed to libcurl with the CURLOPT_WRITEHEADER option. Return the number of bytes actually written or return -1 to signal error to the library (it will cause it to abort the transfer with a CURLE_WRITE_ERROR return code). (Added in 7.7.2)

CURLOPT_WRITEHEADER
    Pass a pointer to be used to write the header part of the received data to. If you don't use your own callback to take care of the writing, this must be a valid FILE *. See also the CURLOPT_HEADERFUNCTION option above on how to set a custom get-all-headers callback.

CURLOPT_DEBUGFUNCTION
    Function pointer that should match the following prototype: int curl_debug_callback (CURL *, curl_infotype, char *, size_t, void *); This function will receive debug information if CURLOPT_VERBOSE is enabled. The curl_infotype argument specifies what kind of information it is. This funtion must return 0. NOTE: the data pointed to by the char * passed to this function WILL NOT be zero terminated, but will be exactly of the size as told by the size_t argument.

CURLOPT_DEBUGDATA
    Pass a pointer to whatever you want passed in to your CURLOPT_DEBUGFUNCTION in the last void * argument. This pointer is not used by libcurl, it is only passed to the callback.

ERROR OPTIONS

CURLOPT_ERRORBUFFER
    Pass a char * to a buffer that the libcurl may store human readable error messages in. This may be more helpful than just the return code from the library. The buffer must be at least CURL_ERROR_SIZE big. Use CURLOPT_VERBOSE and CURLOPT_DEBUGFUNCTION to better debug/trace why errors happen. Note: if the library does not return an error, the buffer may not have been touched. Do not rely on the contents in those cases.

CURLOPT_STDERR
    Pass a FILE * as parameter. This is the stream to use instead of stderr internally when reporting errors.

CURLOPT_FAILONERROR
    A non-zero parameter tells the library to fail silently if the HTTP code returned is equal to or larger than 300. The default action would be to return the page normally, ignoring that code.

NETWORK OPTIONS

CURLOPT_URL
    The actual URL to deal with. The parameter should be a char * to a zero terminated string. The string must remain present until curl no longer needs it, as it doesn't copy the string. NOTE: this option is (the only one) required to be set before curl_easy_perform(3) is called.

CURLOPT_PROXY
    Set HTTP proxy to use. The parameter should be a char * to a zero terminated string holding the host name or dotted IP address. To specify port number in this string, append :[port] to the end of the host name. The proxy string may be prefixed with [protocol]:// since any such prefix will be ignored. The proxy's port number may optionally be specified with the separate option CURLOPT_PROXYPORT. NOTE: when you tell the library to use a HTTP proxy, libcurl will transparently convert operations to HTTP even if you specify a FTP URL etc. This may have an impact on what other features of the library you can use, such as CURLOPT_QUOTE and similar FTP specifics that don't work unless you tunnel through the HTTP proxy. Such tunneling is activated with CURLOPT_HTTPPROXYTUNNEL. NOTE2: libcurl respects the environment variables http_proxy, ftp_proxy, all_proxy etc, if any of those is set.

CURLOPT_PROXYPORT
    Pass a long with this option to set the proxy port to connect to unless it is specified in the proxy string CURLOPT_PROXY.

CURLOPT_PROXYTYPE
    Pass a long with this option to set type of the proxy. Available options for this are CURLPROXY_HTTP and CURLPROXY_SOCKS5, with the HTTP one being default. (Added in 7.10)

CURLOPT_HTTPPROXYTUNNEL
    Set the parameter to non-zero to get the library to tunnel all operations through a given HTTP proxy. Note that there is a big difference between using a proxy and to tunnel through it. If you don't know what this means, you probably don't want this tunneling option. (Added in 7.3)

CURLOPT_INTERFACE
    Pass a char * as parameter. This set the interface name to use as outgoing network interface. The name can be an interface name, an IP address or a host name. (Added in 7.3)

CURLOPT_DNS_CACHE_TIMEOUT
    Pass a long, this sets the timeout in seconds. Name resolves will be kept in memory for this number of seconds. Set to zero (0) to completely disable caching, or set to -1 to make the cached entries remain forever. By default, libcurl caches info for 60 seconds. (Added in 7.9.3)

CURLOPT_DNS_USE_GLOBAL_CACHE
    Pass a long. If the value is non-zero, it tells curl to use a global DNS cache that will survive between easy handle creations and deletions. This is not thread-safe and this will use a global varible. (Added in 7.9.3)

CURLOPT_BUFFERSIZE
    Pass a long specifying your prefered size for the receive buffer in libcurl. The main point of this would be that the write callback gets called more often and with smaller chunks. This is just treated as a request, not an order. You cannot be guaranteed to actually get the given size. (Added in 7.10)

NAMES and PASSWORDS OPTIONS

CURLOPT_NETRC
    This parameter controls the preference of libcurl between using user names and passwords from your ~/.netrc file, relative to user names and passwords in the URL supplied with CURLOPT_URL. Note: libcurl uses a user name (and supplied or prompted password) supplied with CURLOPT_USERPWD in preference to any of the options controlled by this parameter. Pass a long, set to one of the values described below.

    CURL_NETRC_OPTIONAL
        The use of your ~/.netrc file is optional, and information in the URL is to be preferred. The file will be scanned with the host and user name (to find the password only) or with the host only, to find the first user name and password after that machine, which ever information is not specified in the URL. Undefined values of the option will have this effect.

    CURL_NETRC_IGNORED
        The library will ignore the file and use only the information in the URL. This is the default.

    CURL_NETRC_REQUIRED
        This value tells the library that use of the file is required, to ignore the information in the URL, and to search the file with the host only.

Only machine name, user name and password are taken into account
    (init macros and similar things aren't supported). Note: libcurl does not verify that the file has the correct properties set (as the standard Unix ftp client does). It should only be readable by user.

CURLOPT_USERPWD
    Pass a char * as parameter, which should be [user name]:[password] to use for the connection. If the password is left out, you will be prompted for it. CURLOPT_PASSWDFUNCTION can be used to set your own prompt function.

CURLOPT_PROXYUSERPWD
    Pass a char * as parameter, which should be [user name]:[password] to use for the connection to the HTTP proxy. If the password is left out, you will be prompted for it. CURLOPT_PASSWDFUNCTION can be used to set your own prompt function.

HTTP OPTIONS

CURLOPT_ENCODING
    Two encodings are supported dentity, which does nothing, and deflate to request the server to compress its reponse using the zlib algorithm. This is not an order, the server may or may not do it. See the special file lib/README.encoding for details.

CURLOPT_FOLLOWLOCATION
    A non-zero parameter tells the library to follow any Location: header that the server sends as part of a HTTP header. NOTE: this means that the library will re-send the same request on the new location and follow new Location: headers all the way until no more such headers are returned. CURLOPT_MAXREDIRS can be used to limit the number of redirects libcurl will follow.

CURLOPT_MAXREDIRS
    Pass a long. The set number will be the redirection limit. If that many redirections have been followed, the next redirect will cause an error (CURLE_TOO_MANY_REDIRECTS). This option only makes sense if the CURLOPT_FOLLOWLOCATION is used at the same time. (Added in 7.5)

CURLOPT_PUT
    A non-zero parameter tells the library to use HTTP PUT to transfer data. The data should be set with CURLOPT_READDATA and CURLOPT_INFILESIZE.

CURLOPT_POST
    A non-zero parameter tells the library to do a regular HTTP post. This is a normal application/x-www-form-urlencoded kind, which is the most commonly used one by HTML forms. See the CURLOPT_POSTFIELDS option for how to specify the data to post and CURLOPT_POSTFIELDSIZE in how to set the data size. Starting with libcurl 7.8, this option is obsolete. Using the CURLOPT_POSTFIELDS option will imply this option.

CURLOPT_POSTFIELDS
    Pass a char * as parameter, which should be the full data to post in a HTTP post operation. This is a normal application/x-www-form-urlencoded kind, which is the most commonly used one by HTML forms. See also the CURLOPT_POST. Since 7.8, using CURLOPT_POSTFIELDS implies CURLOPT_POST. Note: to make multipart/formdata posts (aka rfc1867-posts), check out the CURLOPT_HTTPPOST option.

CURLOPT_POSTFIELDSIZE
    If you want to post data to the server without letting libcurl do a strlen() to measure the data size, this option must be used. When this option is used you can post fully binary data, which otherwise is likely to fail. If this size is set to zero, the library will use strlen() to get the size. (Added in libcurl 7.2)

CURLOPT_HTTPPOST
    Tells libcurl you want a multipart/formdata HTTP POST to be made and you instruct what data to pass on to the server. Pass a pointer to a linked list of HTTP post structs as parameter. The linked list should be a fully valid list of 'struct HttpPost' structs properly filled in. The best and most elegant way to do this, is to use curl_formadd(3) as documented. The data in this list must remain intact until you close this curl handle again with curl_easy_cleanup(3).

CURLOPT_REFERER
    Pass a pointer to a zero terminated string as parameter. It will be used to set the Referer: header in the http request sent to the remote server. This can be used to fool servers or scripts. You can also set any custom header with CURLOPT_HTTPHEADER.

CURLOPT_USERAGENT
    Pass a pointer to a zero terminated string as parameter. It will be used to set the User-Agent: header in the http request sent to the remote server. This can be used to fool servers or scripts. You can also set any custom header with CURLOPT_HTTPHEADER.

CURLOPT_HTTPHEADER
    Pass a pointer to a linked list of HTTP headers to pass to the server in your HTTP request. The linked list should be a fully valid list of struct curl_slist structs properly filled in. Use curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list. If you add a header that is otherwise generated and used by libcurl internally, your added one will be used instead. If you add a header with no contents as in 'Accept:' (no data on the right side of the colon), the internally used header will get disabled. Thus, using this option you can add new headers, replace internal headers and remove internal headers. The headers included in the linked list must not be CRLF-terminated, because curl adds CRLF after each header item. Failure to comply with this will result in strange bugs because the server will most likely ignore part of the headers you specified. NOTE:The most commonly replaced headers have "shortcuts" in the options CURLOPT_COOKIE, CURLOPT_USERAGENT and CURLOPT_REFERER.

CURLOPT_HTTP200ALIASES
    Pass a pointer to a linked list of aliases to be treated as valid HTTP 200 responses. Some servers respond with a custom header response line. For example, IceCast servers respond with "ICY 200 OK". By including this string in your list of aliases, the response will be treated as a valid HTTP header line such as "HTTP/1.0 200 OK". (Added in 7.10.3) The linked list should be a fully valid list of struct curl_slist structs, and be properly filled in. Use curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list. NOTE:The alias itself is not parsed for any version strings. So if your alias is "MYHTTP/9.9", Libcurl will not treat the server as responding with HTTP version 9.9. Instead Libcurl will use the value set by option CURLOPT_HTTP_VERSION.

CURLOPT_COOKIE
    Pass a pointer to a zero terminated string as parameter. It will be used to set a cookie in the http request. The format of the string should be NAME=CONTENTS, where NAME is the cookie name and CONTENTS is what the cookie should contain. If you need to set mulitple cookies, you need to set them all using a single option and thus you need to concat them all in one single string. Set multiple cookies in one string like this: "name1=content1; name2=content2;" etc. Using this option multiple times will only make the latest string override the previously ones.

CURLOPT_COOKIEFILE
    Pass a pointer to a zero terminated string as parameter. It should contain the name of your file holding cookie data to read. The cookie data may be in Netscape / Mozilla cookie data format or just regular HTTP-style headers dumped to a file. Given an empty or non-existing file, this option will enable cookies for this curl handle, making it understand and parse received cookies and then use matching cookies in future request.

CURLOPT_COOKIEJAR
    Pass a file name as char *, zero terminated. This will make libcurl write all internally known cookies to the specified file when curl_easy_cleanup(3) is called. If no cookies are known, no file will be created. Specify "-" to instead have the cookies written to stdout. Using this option also enables cookies for this session, so if you for example follow a location it will make matching cookies get sent accordingly. (Added in 7.9)

CURLOPT_TIMECONDITION
    Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE time value is treated. You can set this parameter to TIMECOND_IFMODSINCE or TIMECOND_IFUNMODSINCE. This is a HTTP-only feature. (TBD)

CURLOPT_TIMEVALUE
    Pass a long as parameter. This should be the time in seconds since 1 jan 1970, and the time will be used in a condition as specified with CURLOPT_TIMECONDITION.

CURLOPT_HTTPGET
    Pass a long. If the long is non-zero, this forces the HTTP request to get back to GET. Only really usable if POST, PUT or a custom request have been used previously using the same curl handle. (Added in 7.8.1)

CURLOPT_HTTP_VERSION
    Pass a long, set to one of the values described below. They force libcurl to use the specific HTTP versions. This is not sensible to do unless you have a good reason.

    CURL_HTTP_VERSION_NONE
        We don't care about what version the library uses. libcurl will use whatever it thinks fit.

    CURL_HTTP_VERSION_1_0
        Enforce HTTP 1.0 requests.

    CURL_HTTP_VERSION_1_1
        Enforce HTTP 1.1 requests.

FTP OPTIONS

CURLOPT_FTPPORT
    Pass a pointer to a zero terminated string as parameter. It will be used to get the IP address to use for the ftp PORT instruction. The PORT instruction tells the remote server to connect to our specified IP address. The string may be a plain IP address, a host name, an network interface name (under Unix) or just a '-' letter to let the library use your systems default IP address. Default FTP operations are passive, and thus won't use PORT.

CURLOPT_QUOTE
    Pass a pointer to a linked list of FTP commands to pass to the server prior to your ftp request. This will be done before any other FTP commands are issued (even before the CWD command). The linked list should be a fully valid list of to append strings (commands) to the list, and clear the entire list afterwards with curl_slist_free_all(3). Disable this operation again by setting a NULL to this option.

CURLOPT_POSTQUOTE
    Pass a pointer to a linked list of FTP commands to pass to the server after your ftp transfer request. The linked list should be a fully valid list of struct curl_slist structs properly filled in as described for CURLOPT_QUOTE. Disable this operation again by setting a NULL to this option.

CURLOPT_PREQUOTE
    Pass a pointer to a linked list of FTP commands to pass to the server after the transfer type is set. The linked list should be a fully valid list of struct curl_slist structs properly filled in as described for CURLOPT_QUOTE. Disable this operation again by setting a NULL to this option.

CURLOPT_FTPLISTONLY
    A non-zero parameter tells the library to just list the names of an ftp directory, instead of doing a full directory listing that would include file sizes, dates etc. This causes an FTP NLST command to be sent. Beware that some FTP servers list only files in their response to NLST; they might not include subdirectories and symbolic links.

CURLOPT_FTPAPPEND
    A non-zero parameter tells the library to append to the remote file instead of overwrite it. This is only useful when uploading to a ftp site.

CURLOPT_FTP_USE_EPSV
    Pass a long. If the value is non-zero, it tells curl to use the EPSV command when doing passive FTP downloads (which it always does by default). Using EPSV means that it will first attempt to use EPSV before using PASV, but if you pass FALSE (zero) to this option, it will not try using EPSV, only plain PASV.

PROTOCOL OPTIONS

CURLOPT_TRANSFERTEXT
    A non-zero parameter tells the library to use ASCII mode for ftp transfers, instead of the default binary transfer. For LDAP transfers it gets the data in plain text instead of HTML and for win32 systems it does not set the stdout to binary mode. This option can be usable when transferring text data between systems with different views on certain characters, such as newlines or similar.

CURLOPT_CRLF
    Convert Unix newlines to CRLF newlines on transfers.

CURLOPT_RANGE
    Pass a char * as parameter, which should contain the specified range you want. It should be in the format "X-Y", where X or Y may be left out. HTTP transfers also support several intervals, separated with commas as in "X-Y,N-M". Using this kind of multiple intervals will cause the HTTP server to send the response document in pieces (using standard MIME separation techniques).

CURLOPT_RESUME_FROM
    Pass a long as parameter. It contains the offset in number of bytes that you want the transfer to start from.

CURLOPT_CUSTOMREQUEST
    Pass a pointer to a zero terminated string as parameter. It will be user instead of GET or HEAD when doing the HTTP request. This is useful for doing DELETE or other more or less obscure HTTP requests. Don't do this at will, make sure your server supports the command first.

CURLOPT_FILETIME
    Pass a long. If it is a non-zero value, libcurl will attempt to get the modification date of the remote document in this operation. This requires that the remote server sends the time or replies to a time querying command. The curl_easy_getinfo(3) function with the CURLINFO_FILETIME argument can be used after a transfer to extract the received time (if any). (Added in 7.5)

CURLOPT_NOBODY
    A non-zero parameter tells the library to not include the body-part in the output. This is only relevant for protocols that have separate header and body parts.

CURLOPT_INFILESIZE
    When uploading a file to a remote site, this option should be used to tell libcurl what the expected size of the infile is.

CURLOPT_UPLOAD
    A non-zero parameter tells the library to prepare for an upload. The CURLOPT_READDATA and CURLOPT_INFILESIZE are also interesting for uploads.

CONNECTION OPTIONS

CURLOPT_TIMEOUT
    Pass a long as parameter containing the maximum time in seconds that you allow the libcurl transfer operation to take. Normally, name lookups can take a considerable time and limiting operations to less than a few minutes risk aborting perfectly normal operations. This option will cause curl to use the SIGALRM to enable time-outing system calls. NOTE: this is not recommended to use in unix multi-threaded programs, as it uses signals unless CURLOPT_NOSIGNAL (see above) is set.

CURLOPT_LOW_SPEED_LIMIT
    Pass a long as parameter. It contains the transfer speed in bytes per second that the transfer should be below during CURLOPT_LOW_SPEED_TIME seconds for the library to consider it too slow and abort.

CURLOPT_LOW_SPEED_TIME
    Pass a long as parameter. It contains the time in seconds that the transfer should be below the CURLOPT_LOW_SPEED_LIMIT for the library to consider it too slow and abort.

CURLOPT_MAXCONNECTS
    Pass a long. The set number will be the persistent connection cache size. The set amount will be the maximum amount of simultaneously open connections that libcurl may cache. Default is 5, and there isn't much point in changing this value unless you are perfectly aware of how this work and changes libcurl's behaviour. This concerns connection using any of the protocols that support persistent connections. When reaching the maximum limit, curl uses the CURLOPT_CLOSEPOLICY to figure out which of the existing connections to close to prevent the number of open connections to increase. NOTE: if you already have performed transfers with this curl handle, setting a smaller MAXCONNECTS than before may cause open connections to get closed unnecessarily. (Added in 7.7)

CURLOPT_CLOSEPOLICY
    Pass a long. This option sets what policy libcurl should use when the connection cache is filled and one of the open connections has to be closed to make room for a new connection. This must be one of the CURLCLOSEPOLICY_* defines. Use CURLCLOSEPOLICY_LEAST_RECENTLY_USED to make libcurl close the connection that was least recently used, that connection is also least likely to be capable of re-use. Use CURLCLOSEPOLICY_OLDEST to make libcurl close the oldest connection, the one that was created first among the ones in the connection cache. The other close policies are not support yet. (Added in 7.7)

CURLOPT_FRESH_CONNECT
    Pass a long. Set to non-zero to make the next transfer use a new (fresh) connection by force. If the connection cache is full before this connection, one of the existing connections will be closed as according to the selected or default policy. This option should be used with caution and only if you understand what it does. Set this to 0 to have libcurl attempt re-using an existing connection (default behavior). (Added in 7.7)

CURLOPT_FORBID_REUSE
    Pass a long. Set to non-zero to make the next transfer explicitly close the connection when done. Normally, libcurl keep all connections alive when done with one transfer in case there comes a succeeding one that can re-use them. This option should be used with caution and only if you understand what it does. Set to 0 to have libcurl keep the connection open for possibly later re-use (default behavior). (Added in 7.7)

CURLOPT_CONNECTTIMEOUT
    Pass a long. It should contain the maximum time in seconds that you allow the connection to the server to take. This only limits the connection phase, once it has connected, this option is of no more use. Set to zero to disable connection timeout (it will then only timeout on the system's internal timeouts). See also the CURLOPT_TIMEOUT option. NOTE: this is not recommended to use in unix multi-threaded programs, as it uses signals unless CURLOPT_NOSIGNAL (see above) is set.

SSL and SECURITY OPTIONS

CURLOPT_SSLCERT
    Pass a pointer to a zero terminated string as parameter. The string should be the file name of your certificate. The default format is "PEM" and can be changed with CURLOPT_SSLCERTTYPE.

CURLOPT_SSLCERTTYPE
    Pass a pointer to a zero terminated string as parameter. The string should be the format of your certificate. Supported formats are "PEM" and "DER". (Added in 7.9.3)

CURLOPT_SSLCERTPASSWD
    Pass a pointer to a zero terminated string as parameter. It will be used as the password required to use the CURLOPT_SSLCERT certificate. If the password is not supplied, you will be prompted for it. CURLOPT_PASSWDFUNCTION can be used to set your own prompt function. NOTE:This option is replaced by CURLOPT_SSLKEYPASSWD and only cept for backward compatibility. You never needed a pass phrase to load a certificate but you need one to load your private key.

CURLOPT_SSLKEY
    Pass a pointer to a zero terminated string as parameter. The string should be the file name of your private key. The default format is "PEM" and can be changed with CURLOPT_SSLKEYTYPE. (Added in 7.9.3)

CURLOPT_SSLKEYTYPE
    Pass a pointer to a zero terminated string as parameter. The string should be the format of your private key. Supported formats are "PEM", "DER" and "ENG". (Added in 7.9.3) NOTE:The format "ENG" enables you to load the private key from a crypto engine. in this case CURLOPT_SSLKEY is used as an identifier passed to the engine. You have to set the crypto engine with CURLOPT_SSL_ENGINE.

CURLOPT_SSLKEYPASSWD
    Pass a pointer to a zero terminated string as parameter. It will be used as the password required to use the CURLOPT_SSLKEY private key. If the password is not supplied, you will be prompted for it. CURLOPT_PASSWDFUNCTION can be used to set your own prompt function. (Added in 7.9.3)

CURLOPT_SSL_ENGINE
    Pass a pointer to a zero terminated string as parameter. It will be used as the identifier for the crypto engine you want to use for your private key. (Added in 7.9.3) NOTE:If the crypto device cannot be loaded, CURLE_SSL_ENGINE_NOTFOUND is returned.

CURLOPT_SSL_ENGINEDEFAULT
    Sets the actual crypto engine as the default for (asymetric) crypto operations. (Added in 7.9.3) NOTE:If the crypto device cannot be set, CURLE_SSL_ENGINE_SETFAILED is returned.

CURLOPT_SSLVERSION
    Pass a long as parameter. Set what version of SSL to attempt to use, 2 or 3. By default, the SSL library will try to solve this by itself although some servers make this difficult why you at times may have to use this option.

CURLOPT_SSL_VERIFYPEER
    Pass a long that is set to a zero value to stop curl from verifying the peer's certificate (7.10 starting setting this option to TRUE by default). Alternate certificates to verify against can be specified with the CURLOPT_CAINFO option (Added in 7.4.2) or a certificate directory can be specified with the CURLOPT_CAPATH option (Added in 7.9.8). As of 7.10, curl installs a default bundle. CURLOPT_SSL_VERIFYHOST may also need to be set to 1 or 0 if CURLOPT_SSL_VERIFYPEER is disabled (it defaults to 2).

CURLOPT_CAINFO
    Pass a char * to a zero terminated string naming a file holding one or more certificates to verify the peer with. This only makes sense when used in combination with the CURLOPT_SSL_VERIFYPEER option. (Added in 7.4.2)

CURLOPT_CAPATH
    Pass a char * to a zero terminated string naming a directory holding multiple CA certificates to verify the peer with. The certificate directory must be prepared using the openssl c_rehash utility. This only makes sense when used in combination with the CURLOPT_SSL_VERIFYPEER option. The CAPATH function apparently does not work in Windows due to some limitation in openssl. (Added in 7.9.8)

CURLOPT_RANDOM_FILE
    Pass a char * to a zero terminated file name. The file will be used to read from to seed the random engine for SSL. The more random the specified file is, the more secure the SSL connection will become.

CURLOPT_EGDSOCKET
    Pass a char * to the zero terminated path name to the Entropy Gathering Daemon socket. It will be used to seed the random engine for SSL.

CURLOPT_SSL_VERIFYHOST
    Pass a long. Set if we should verify the Common name from the peer certificate in the SSL handshake, set 1 to check existence, 2 to ensure that it matches the provided hostname. This is by default set to 2. (Added in 7.8.1, default changed in 7.10)

CURLOPT_SSL_CIPHER_LIST
    Pass a char *, pointing to a zero terminated string holding the list of ciphers to use for the SSL connection. The list must be syntactly correct, it consists of one or more cipher strings separated by colons. Commas or spaces are also acceptable separators but colons are normally used, , - and + can be used as operators. Valid examples of cipher lists include 'RC4-SHA', 'SHA1+DES', 'TLSv1' and 'DEFAULT'. The default list is normally set when you compile OpenSSL. You'll find more details about cipher lists on this URL: http://www.openssl.org/docs/apps/ciphers.html

CURLOPT_KRB4LEVEL
    Pass a char * as parameter. Set the krb4 security level, this also enables krb4 awareness. This is a string, 'clear', 'safe', 'confidential' or 'private'. If the string is set but doesn't match one of these, 'private' will be used. Set the string to NULL to disable kerberos4. The kerberos support only works for FTP. (Added in 7.3)

OTHER OPTIONS

CURLOPT_PRIVATE
    Pass a char * as parameter, pointing to data that should be associated with the curl handle. The pointer can be subsequently retrieved using the CURLINFO_PRIVATE options to curl_easy_getinfo. (Added in 7.10.3)

RETURN VALUE
CURLE_OK (zero) means that the option was set properly, non-zero means an error occurred as <curl/curl.h> defines. See the libcurl-errors.3 man page for the full list with descriptions.

SEE ALSO
curl_easy_init(3), curl_easy_cleanup(3),

BUGS
If you find any bugs, or just have questions, subscribe to one of the mailing lists and post. We won't bite.