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curl_easy_setopt(3) libcurl Manual 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, an object pointer or a curl_off_t,
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 applica-tion application
tion uses many curl_easy_setopt() calls in the setup phase.
Options set with this function call are valid for all forthcoming transfers performed using this han-dle. handle.
dle. 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. You can optionally reset all
options back to internal default with curl_easy_reset(3).
Strings passed to libcurl as 'char *' arguments, are copied by the library; thus the string storage
associated to the pointer argument may be overwritten after curl_easy_setopt() returns. Exceptions to
this rule are described in the option details below.
Before version 7.17.0, strings were not copied. Instead the user was forced keep them available until
libcurl no longer needed them.
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 1 to get the library to display a lot of verbose information about its
operations. Very useful for libcurl and/or protocol debugging and understanding. The verbose
information will be sent to stderr, or the stream set with CURLOPT_STDERR. The default value
for this parameter is 0.
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 parameter set to 1 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). The default
value for this parameter is 0.
CURLOPT_NOPROGRESS
Pass a long. If set to 1, it tells the library to shut off the progress meter completely. It
will also prevent the CURLOPT_PROGRESSFUNCTION from getting called. The default value for this
parameter is 1.
Future versions of libcurl are likely to not have any built-in progress meter at all.
CURLOPT_NOSIGNAL
Pass a long. If it is 1, 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 risk-ing risking
ing getting signals. The default value for this parameter is 0. (Added in 7.10)
If this option is set and libcurl has been built with the standard name resolver, timeouts
will not occur while the name resolve takes place. Consider building libcurl with c-ares sup-port support
port to enable asynchronous DNS lookups, which enables nice timeouts for name resolves without
signals.
Setting CURLOPT_NOSIGNAL to 1 makes libcurl NOT ask the system to ignore SIGPIPE signals,
which otherwise are sent by the system when trying to send data to a socket which is closed in
the other end. libcurl makes an effort to never cause such SIGPIPEs to trigger, but some oper-ating operating
ating systems have no way to avoid them and even on those that have there are some corner
cases when they may still happen, contrary to our desire. In addition, using CURLAUTH_NTLM_WB
authentication could cause a SIGCHLD signal to be raised.
CURLOPT_WILDCARDMATCH
Set this option to 1 if you want to transfer multiple files according to a file name pattern.
The pattern can be specified as part of the CURLOPT_URL option, using an fnmatch-like pattern
(Shell Pattern Matching) in the last part of URL (file name).
By default, libcurl uses its internal wildcard matching implementation. You can provide your
own matching function by the CURLOPT_FNMATCH_FUNCTION option.
This feature is only supported by the FTP download for now.
A brief introduction of its syntax follows:
* - ASTERISK
ftp://example.com/some/path/*.txt (for all txt's from the root directory)
? - QUESTION MARK
Question mark matches any (exactly one) character.
ftp://example.com/some/path/photo?.jpeg
[ - BRACKET EXPRESSION
The left bracket opens a bracket expression. The question mark and asterisk have no
special meaning in a bracket expression. Each bracket expression ends by the right
bracket and matches exactly one character. Some examples follow:
[a-zA-Z0-9] or [f-gF-G] - character interval
[abc] - character enumeration
[^abc] or [!abc] - negation
[[:name:]] class expression. Supported classes are alnum,lower, space, alpha, digit,
print, upper, blank, graph, xdigit.
[][-!^] - special case - matches only '-', ']', '[', '!' or '^'. These characters have
no special purpose.
[\[\]\\] - escape syntax. Matches '[', ']' or '\'.
Using the rules above, a file name pattern can be constructed:
ftp://example.com/some/path/[a-z[:upper:]\\].jpeg
(This was added in 7.21.0)
CALLBACK OPTIONS
CURLOPT_WRITEFUNCTION
Pass a pointer to a function that matches the following prototype: size_t function( char *ptr,
size_t size, size_t nmemb, void *userdata); This function gets called by libcurl as soon as
there is data received 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. This will abort the transfer and return CURLE_WRITE_ERROR.
From 7.18.0, the function can return CURL_WRITEFUNC_PAUSE which then will cause writing to
this connection to become paused. See curl_easy_pause(3) for further details.
This function may be called with zero bytes data if the transferred file is empty.
Set this option to NULL to get the internal default function. The internal default function
will write the data to the FILE * given with CURLOPT_WRITEDATA.
Set the userdata argument with the CURLOPT_WRITEDATA option.
The callback function 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
body data that can be passed to the write callback is defined in the curl.h header file:
CURL_MAX_WRITE_SIZE (the usual default is 16K). If you however have CURLOPT_HEADER set, which
sends header data to the write callback, you can get up to CURL_MAX_HTTP_HEADER bytes of
header data passed into it. This usually means 100K.
CURLOPT_WRITEDATA
Data pointer to pass to the file write function. If you use the CURLOPT_WRITEFUNCTION option,
this is the pointer you'll get as input. If you don't use a callback, you must pass a 'FILE *'
(cast to 'void *') as libcurl will pass this to fwrite() when writing data. By default, the
value of this parameter is unspecified.
The internal CURLOPT_WRITEFUNCTION will write the data to the FILE * given with this option,
or to stdout if this option hasn't been set.
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
Pass a pointer to a function that matches the following prototype: size_t function( void *ptr,
size_t size, size_t nmemb, void *userdata); 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.
If you stop the current transfer by returning 0 "pre-maturely" (i.e before the server expected
it, like when you've said you will upload N bytes and you upload less than N bytes), you may
experience that the server "hangs" waiting for the rest of the data that won't come.
The read callback may return CURL_READFUNC_ABORT to stop the current operation immediately,
resulting in a CURLE_ABORTED_BY_CALLBACK error code from the transfer (Added in 7.12.1)
From 7.18.0, the function can return CURL_READFUNC_PAUSE which then will cause reading from
this connection to become paused. See curl_easy_pause(3) for further details.
Bugs: when doing TFTP uploads, you must return the exact amount of data that the callback
wants, or it will be considered the final packet by the server end and the transfer will end
there.
If you set this callback pointer to NULL, or don't set it at all, the default internal read
function will be used. It is doing an fread() on the FILE * userdata set with CURLOPT_READ-DATA. CURLOPT_READDATA.
DATA.
CURLOPT_READDATA
Data pointer to pass to the file read function. If you use the CURLOPT_READFUNCTION option,
this is the pointer you'll get as input. If you don't specify a read callback but instead rely
on the default internal read function, this data must be a valid readable FILE * (cast to
'void *').
If you're using libcurl as a win32 DLL, you MUST use a CURLOPT_READFUNCTION if you set this
option.
This option was also known by the older name CURLOPT_INFILE, the name CURLOPT_READDATA was
introduced in 7.9.7.
CURLOPT_IOCTLFUNCTION
Pass a pointer to a function that matches the following prototype: curlioerr function(CURL
*handle, int cmd, void *clientp);. This function gets called by libcurl when something special
I/O-related needs to be done that the library can't do by itself. For now, rewinding the read
data stream is the only action it can request. The rewinding of the read data stream may be
necessary when doing a HTTP PUT or POST with a multi-pass authentication method. By default,
this parameter is set to NULL. (Option added in 7.12.3).
Use CURLOPT_SEEKFUNCTION instead to provide seeking! If CURLOPT_SEEKFUNCTION is set, this
parameter will be ignored when seeking.
CURLOPT_IOCTLDATA
Pass a pointer that will be untouched by libcurl and passed as the 3rd argument in the ioctl
callback set with CURLOPT_IOCTLFUNCTION. By default, the value of this parameter is unspeci-fied. unspecified.
fied. (Option added in 7.12.3)
CURLOPT_SEEKFUNCTION
Pass a pointer to a function that matches the following prototype: int function(void
*instream, curl_off_t offset, int origin); This function gets called by libcurl to seek to a
certain position in the input stream and can be used to fast forward a file in a resumed
upload (instead of reading all uploaded bytes with the normal read function/callback). It is
also called to rewind a stream when doing a HTTP PUT or POST with a multi-pass authentication
method. The function shall work like "fseek" or "lseek" and accepted SEEK_SET, SEEK_CUR and
SEEK_END as argument for origin, although (in 7.18.0) libcurl only passes SEEK_SET. The call-back callback
back must return 0 (CURL_SEEKFUNC_OK) on success, 1 (CURL_SEEKFUNC_FAIL) to cause the upload
operation to fail or 2 (CURL_SEEKFUNC_CANTSEEK) to indicate that while the seek failed,
libcurl is free to work around the problem if possible. The latter can sometimes be done by
instead reading from the input or similar.
By default, this parameter is unset.
If you forward the input arguments directly to "fseek" or "lseek", note that the data type for
offset is not the same as defined for curl_off_t on many systems! (Option added in 7.18.0)
CURLOPT_SEEKDATA
Data pointer to pass to the file seek function. If you use the CURLOPT_SEEKFUNCTION option,
this is the pointer you'll get as input. If you don't specify a seek callback, NULL is passed.
(Option added in 7.18.0)
CURLOPT_SOCKOPTFUNCTION
Pass a pointer to a function that matches the following prototype: int function(void *clientp,
curl_socket_t curlfd, curlsocktype purpose);. By default, this parameter is unset. If set,
this function gets called by libcurl after the socket() call but before the connect() call.
The callback's purpose argument identifies the exact purpose for this particular socket:
CURLSOCKTYPE_IPCXN for actively created connections or since 7.28.0 CURLSOCKTYPE_ACCEPT for
FTP when the connection was setup with PORT/EPSV (in earlier versions these sockets weren't
passed to this callback).
Future versions of libcurl may support more purposes. It passes the newly created socket
descriptor so additional setsockopt() calls can be done at the user's discretion. Return 0
(zero) from the callback on success. Return 1 from the callback function to signal an unrecov-erable unrecoverable
erable error to the library and it will close the socket and return CURLE_COULDNT_CONNECT.
(Option added in 7.16.0)
Added in 7.21.5, the callback function may return CURL_SOCKOPT_ALREADY_CONNECTED, which tells
libcurl that the socket is in fact already connected and then libcurl will not attempt to con-nect connect
nect it.
CURLOPT_SOCKOPTDATA
Pass a pointer that will be untouched by libcurl and passed as the first argument in the sock-opt sockopt
opt callback set with CURLOPT_SOCKOPTFUNCTION. The default value of this parameter is unspec-ified. unspecified.
ified. (Option added in 7.16.0)
CURLOPT_OPENSOCKETFUNCTION
Pass a pointer to a function that matches the following prototype: curl_socket_t function(void
*clientp, curlsocktype purpose, struct curl_sockaddr *address);. This function gets called by
libcurl instead of the socket(2) call. The callback's purpose argument identifies the exact
purpose for this particular socket: CURLSOCKTYPE_IPCXN is for IP based connections. Future
versions of libcurl may support more purposes. It passes the resolved peer address as a
address argument so the callback can modify the address or refuse to connect at all. The call-back callback
back function should return the socket or CURL_SOCKET_BAD in case no connection could be
established or another error was detected. Any additional setsockopt(2) calls can be done on
the socket at the user's discretion. CURL_SOCKET_BAD return value from the callback function
will signal an unrecoverable error to the library and it will return CURLE_COULDNT_CONNECT.
This return code can be used for IP address blacklisting. The default behavior is:
return socket(addr->family, addr->socktype, addr->protocol);
(Option added in 7.17.1.)
CURLOPT_OPENSOCKETDATA
Pass a pointer that will be untouched by libcurl and passed as the first argument in the
opensocket callback set with CURLOPT_OPENSOCKETFUNCTION. The default value of this parameter
is unspecified. (Option added in 7.17.1.)
CURLOPT_CLOSESOCKETFUNCTION
Pass a pointer to a function that matches the following prototype: int function(void *clientp,
curl_socket_t item);. This function gets called by libcurl instead of the close(3) or clos-esocket(3) closesocket(3)
esocket(3) call when sockets are closed (not for any other file descriptors). This is pretty
much the reverse to the CURLOPT_OPENSOCKETFUNCTION option. Return 0 to signal success and 1 if
there was an error. (Option added in 7.21.7)
CURLOPT_CLOSESOCKETDATA
Pass a pointer that will be untouched by libcurl and passed as the first argument in the clos-esocket closesocket
esocket callback set with CURLOPT_CLOSESOCKETFUNCTION. The default value of this parameter is
unspecified. (Option added in 7.21.7)
CURLOPT_PROGRESSFUNCTION
Pass a pointer to a function that matches the following prototype: int function(void *clientp,
double dltotal, double dlnow, double ultotal, double ulnow); . This function gets called by
libcurl instead of its internal equivalent with a frequent interval during operation (roughly
once per second or sooner) no matter if data is being transferred or not. Unknown/unused
argument values passed to the callback 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.
If you transfer data with the multi interface, this function will not be called during periods
of idleness unless you call the appropriate libcurl function that performs transfers.
CURLOPT_NOPROGRESS must be set to 0 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. The default value of this parameter is
unspecified.
CURLOPT_HEADERFUNCTION
Pass a pointer to a function that matches the following prototype: size_t function( void *ptr,
size_t size, size_t nmemb, void *userdata);. This function gets called by libcurl as soon as
it has received header data. The header callback will be called once for each header and only
complete header lines are passed on to the callback. Parsing headers is very easy using this.
The size of the data pointed to by ptr is size multiplied with nmemb. Do not assume that the
header line is zero terminated! The pointer named userdata is the one you set with the CUR-LOPT_WRITEHEADER CURLOPT_WRITEHEADER
LOPT_WRITEHEADER option. The callback function must 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. This will abort the transfer and return CURL_WRITE_ERROR.
A complete HTTP header that is passed to this function can be up to CURL_MAX_HTTP_HEADER
(100K) bytes.
If this option is not set, or if it is set to NULL, but CURLOPT_HEADERDATA (CURLOPT_WRITE-HEADER) (CURLOPT_WRITEHEADER)
HEADER) is set to anything but NULL, the function used to accept response data will be used
instead. That is, it will be the function specified with CURLOPT_WRITEFUNCTION, or if it is
not specified or NULL - the default, stream-writing function.
It's important to note that the callback will be invoked for the headers of all responses
received after initiating a request and not just the final response. This includes all
responses which occur during authentication negotiation. If you need to operate on only the
headers from the final response, you will need to collect headers in the callback yourself and
use HTTP status lines, for example, to delimit response boundaries.
When a server sends a chunked encoded transfer, it may contain a trailer. That trailer is
identical to a HTTP header and if such a trailer is received it is passed to the application
using this callback as well. There are several ways to detect it being a trailer and not an
ordinary header: 1) it comes after the response-body. 2) it comes after the final header line
(CR LF) 3) a Trailer: header among the regular response-headers mention what header(s) to
expect in the trailer.
For non-HTTP protocols like FTP, POP3, IMAP and SMTP this function will get called with the
server responses to the commands that libcurl sends.
CURLOPT_WRITEHEADER
(This option is also known as CURLOPT_HEADERDATA) Pass a pointer to be used to write the
header part of the received data to. If you don't use CURLOPT_WRITEFUNCTION or CURLOPT_HEADER-FUNCTION CURLOPT_HEADERFUNCTION
FUNCTION to take care of the writing, this must be a valid FILE * as the internal default will
then be a plain fwrite(). See also the CURLOPT_HEADERFUNCTION option above on how to set a
custom get-all-headers callback.
CURLOPT_DEBUGFUNCTION
Pass a pointer to a function that matches the following prototype: int curl_debug_callback
(CURL *, curl_infotype, char *, size_t, void *); CURLOPT_DEBUGFUNCTION replaces the standard
debug function used when CURLOPT_VERBOSE is in effect. This callback receives debug informa-tion, information,
tion, as specified with the curl_infotype argument. This function must return 0. 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.
Available curl_infotype values:
CURLINFO_TEXT
The data is informational text.
CURLINFO_HEADER_IN
The data is header (or header-like) data received from the peer.
CURLINFO_HEADER_OUT
The data is header (or header-like) data sent to the peer.
CURLINFO_DATA_IN
The data is protocol data received from the peer.
CURLINFO_DATA_OUT
The data is protocol data sent to the peer.
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.
CURLOPT_SSL_CTX_FUNCTION
This option does only function for libcurl powered by OpenSSL. If libcurl was built against
another SSL library, this functionality is absent.
Pass a pointer to a function that matches the following prototype: CURLcode sslctxfun(CURL
*curl, void *sslctx, void *parm); This function gets called by libcurl just before the ini-tialization initialization
tialization of a SSL connection after having processed all other SSL related options to give a
last chance to an application to modify the behaviour of openssl's ssl initialization. The
sslctx parameter is actually a pointer to an openssl SSL_CTX. If an error is returned no
attempt to establish a connection is made and the perform operation will return the error code
from this callback function. Set the parm argument with the CURLOPT_SSL_CTX_DATA option. This
option was introduced in 7.11.0.
This function will get called on all new connections made to a server, during the SSL negotia-tion. negotiation.
tion. The SSL_CTX pointer will be a new one every time.
To use this properly, a non-trivial amount of knowledge of the openssl libraries is necessary.
For example, using this function allows you to use openssl callbacks to add additional valida-tion validation
tion code for certificates, and even to change the actual URI of a HTTPS request (example used
in the lib509 test case). See also the example section for a replacement of the key, certifi-cate certificate
cate and trust file settings.
CURLOPT_SSL_CTX_DATA
Data pointer to pass to the ssl context callback set by the option CURLOPT_SSL_CTX_FUNCTION,
this is the pointer you'll get as third parameter, otherwise NULL. (Added in 7.11.0)
CURLOPT_CONV_TO_NETWORK_FUNCTION
CURLOPT_CONV_FROM_NETWORK_FUNCTION
CURLOPT_CONV_FROM_UTF8_FUNCTION
Pass a pointer to a function that matches the following prototype: CURLcode function(char
*ptr, size_t length);
These three options apply to non-ASCII platforms only. They are available only if
CURL_DOES_CONVERSIONS was defined when libcurl was built. When this is the case, curl_ver-sion_info(3) curl_version_info(3)
sion_info(3) will return the CURL_VERSION_CONV feature bit set.
The data to be converted is in a buffer pointed to by the ptr parameter. The amount of data
to convert is indicated by the length parameter. The converted data overlays the input data
in the buffer pointed to by the ptr parameter. CURLE_OK should be returned upon successful
conversion. A CURLcode return value defined by curl.h, such as CURLE_CONV_FAILED, should be
returned if an error was encountered.
CURLOPT_CONV_TO_NETWORK_FUNCTION and CURLOPT_CONV_FROM_NETWORK_FUNCTION convert between the
host encoding and the network encoding. They are used when commands or ASCII data are
sent/received over the network.
CURLOPT_CONV_FROM_UTF8_FUNCTION is called to convert from UTF8 into the host encoding. It is
required only for SSL processing.
If you set a callback pointer to NULL, or don't set it at all, the built-in libcurl iconv
functions will be used. If HAVE_ICONV was not defined when libcurl was built, and no callback
has been established, conversion will return the CURLE_CONV_REQD error code.
If HAVE_ICONV is defined, CURL_ICONV_CODESET_OF_HOST must also be defined. For example:
#define CURL_ICONV_CODESET_OF_HOST "IBM-1047"
The iconv code in libcurl will default the network and UTF8 codeset names as follows:
#define CURL_ICONV_CODESET_OF_NETWORK "ISO8859-1"
#define CURL_ICONV_CODESET_FOR_UTF8 "UTF-8"
You will need to override these definitions if they are different on your system.
CURLOPT_INTERLEAVEFUNCTION
Pass a pointer to a function that matches the following prototype: size_t function( void *ptr,
size_t size, size_t nmemb, void *userdata). This function gets called by libcurl as soon as it
has received interleaved RTP data. This function gets called for each $ block and therefore
contains exactly one upper-layer protocol unit (e.g. one RTP packet). Curl writes the inter-leaved interleaved
leaved header as well as the included data for each call. The first byte is always an ASCII
dollar sign. The dollar sign is followed by a one byte channel identifier and then a 2 byte
integer length in network byte order. See RFC2326 Section 1_.12 for more information on how
RTP interleaving behaves. If unset or set to NULL, curl will use the default write function.
Interleaved RTP poses some challenges for the client application. Since the stream data is
sharing the RTSP control connection, it is critical to service the RTP in a timely fashion. If
the RTP data is not handled quickly, subsequent response processing may become unreasonably
delayed and the connection may close. The application may use CURL_RTSPREQ_RECEIVE to service
RTP data when no requests are desired. If the application makes a request, (e.g.
CURL_RTSPREQ_PAUSE) then the response handler will process any pending RTP data before marking
the request as finished. (Added in 7.20.0)
CURLOPT_INTERLEAVEDATA
This is the userdata pointer that will be passed to CURLOPT_INTERLEAVEFUNCTION when inter-leaved interleaved
leaved RTP data is received. (Added in 7.20.0)
CURLOPT_CHUNK_BGN_FUNCTION
Pass a pointer to a function that matches the following prototype: long function (const void
*transfer_info, void *ptr, int remains). This function gets called by libcurl before a part of
the stream is going to be transferred (if the transfer supports chunks).
This callback makes sense only when using the CURLOPT_WILDCARDMATCH option for now.
The target of transfer_info parameter is a "feature depended" structure. For the FTP wildcard
download, the target is curl_fileinfo structure (see curl/curl.h). The parameter ptr is a
pointer given by CURLOPT_CHUNK_DATA. The parameter remains contains number of chunks remaining
per the transfer. If the feature is not available, the parameter has zero value.
Return CURL_CHUNK_BGN_FUNC_OK if everything is fine, CURL_CHUNK_BGN_FUNC_SKIP if you want to
skip the concrete chunk or CURL_CHUNK_BGN_FUNC_FAIL to tell libcurl to stop if some error
occurred. (This was added in 7.21.0)
CURLOPT_CHUNK_END_FUNCTION
Pass a pointer to a function that matches the following prototype: long function(void *ptr).
This function gets called by libcurl as soon as a part of the stream has been transferred (or
skipped).
Return CURL_CHUNK_END_FUNC_OK if everything is fine or CURL_CHUNK_END_FUNC_FAIL to tell the
lib to stop if some error occurred. (This was added in 7.21.0)
CURLOPT_CHUNK_DATA
Pass a pointer that will be untouched by libcurl and passed as the ptr argument to the
CURL_CHUNK_BGN_FUNTION and CURL_CHUNK_END_FUNTION. (This was added in 7.21.0)
CURLOPT_FNMATCH_FUNCTION
Pass a pointer to a function that matches the following prototype: int function(void *ptr,
const char *pattern, const char *string) prototype (see curl/curl.h). It is used internally
for the wildcard matching feature.
Return CURL_FNMATCHFUNC_MATCH if pattern matches the string, CURL_FNMATCHFUNC_NOMATCH if not
or CURL_FNMATCHFUNC_FAIL if an error occurred. (This was added in 7.21.0)
CURLOPT_FNMATCH_DATA
Pass a pointer that will be untouched by libcurl and passed as the ptr argument to the
CURL_FNMATCH_FUNCTION. (This was added in 7.21.0)
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 curl_easy_perform. The buffer must be at
least CURL_ERROR_SIZE big. Although this argument is a 'char *', it does not describe an
input string. Therefore the (probably undefined) contents of the buffer is NOT copied by the
library. You must keep the associated storage available until libcurl no longer needs it.
Failing to do so will cause very odd behavior or even crashes. libcurl will need it until you
call curl_easy_cleanup(3) or you set the same option again to use a different pointer.
Use CURLOPT_VERBOSE and CURLOPT_DEBUGFUNCTION to better debug/trace why errors happen.
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. Tell libcurl to use this stream instead of stderr when showing the
progress meter and displaying CURLOPT_VERBOSE data.
CURLOPT_FAILONERROR
A parameter set to 1 tells the library to fail silently if the HTTP code returned is equal to
or larger than 400. The default action would be to return the page normally, ignoring that
code.
This method is not fail-safe and there are occasions where non-successful response codes will
slip through, especially when authentication is involved (response codes 401 and 407).
You might get some amounts of headers transferred before this situation is detected, like when
a "100-continue" is received as a response to a POST/PUT and a 401 or 407 is received immedi-ately immediately
ately afterwards.
NETWORK OPTIONS
CURLOPT_URL
Pass in a pointer to the actual URL to deal with. The parameter should be a char * to a zero
terminated string which must be URL-encoded in the following format:
scheme://host:port/path
For a greater explanation of the format please see RFC3986.
If the given URL lacks the scheme, or protocol, part ("http://" or "ftp://" etc), libcurl will
attempt to resolve which protocol to use based on the given host mame. If the protocol is not
supported, libcurl will return (CURLE_UNSUPPORTED_PROTOCOL) when you call curl_easy_perform(3)
or curl_multi_perform(3). Use curl_version_info(3) for detailed information on which protocols
are supported.
The host part of the URL contains the address of the server that you want to connect to. This
can be the fully qualified domain name of the server, the local network name of the machine on
your network or the IP address of the server or machine represented by either an IPv4 or IPv6
address. For example:
http://www .example.com/
http://hostname/
http://192.168.0.1/
http://[2001:1890:1112:1::20]/
It is also possible to specify the user name and password as part of the host, for some proto-cols, protocols,
cols, when connecting to servers that require authentication.
For example the following types of authentication support this:
http://user:password@www.example.com
ftp://user:password@ftp.example.com
pop3://user:password@mail.example.com
The port is optional and when not specified libcurl will use the default port based on the
determined or specified protocol: 80 for HTTP, 21 for FTP and 25 for SMTP, etc. The following
examples show how to specify the port:
http://www.example.com:8080/ - This will connect to a web server using port 8080 rather than
80.
smtp://mail.example.com:587/ - This will connect to a SMTP server on the alternative mail
port.
The path part of the URL is protocol specific and whilst some examples are given below this
list is not conclusive:
HTTP
The path part of a HTTP request specifies the file to retrieve and from what directory. If the
directory is not specified then the web server's root directory is used. If the file is omit-ted omitted
ted then the default document will be retrieved for either the directory specified or the root
directory. The exact resource returned for each URL is entirely dependent on the server's con-figuration. configuration.
figuration.
http://www.example.com - This gets the main page from the web server.
http://www.example.com/index.html - This returns the main page by explicitly requesting it.
http://www.example.com/contactus/ - This returns the default document from the contactus
directory.
FTP
The path part of an FTP request specifies the file to retrieve and from what directory. If the
file part is omitted then libcurl downloads the directory listing for the directory specified.
If the directory is omitted then the directory listing for the root / home directory will be
returned.
ftp://ftp.example.com - This retrieves the directory listing for the root directory.
ftp://ftp.example.com/readme.txt - This downloads the file readme.txt from the root directory.
ftp://ftp.example.com/libcurl/readme.txt - This downloads readme.txt from the libcurl direc-tory. directory.
tory.
ftp://user:password@ftp.example.com/readme.txt - This retrieves the readme.txt file from the
user's home directory. When a username and password is specified, everything that is specified
in the path part is relative to the user's home directory. To retrieve files from the root
directory or a directory underneath the root directory then the absolute path must be speci-fied specified
fied by prepending an additional forward slash to the beginning of the path.
ftp://user:password@ftp.example.com//readme.txt - This retrieves the readme.txt from the root
directory when logging in as a specified user.
SMTP
The path part of a SMTP request specifies the host name to present during communication with
the mail server. If the path is omitted then libcurl will attempt to resolve the local com-puter's computer's
puter's host name. However, this may not return the fully qualified domain name that is
required by some mail servers and specifying this path allows you to set an alternative name,
such as your machine's fully qualified domain name, which you might have obtained from an
external function such as gethostname or getaddrinfo.
smtp://mail.example.com - This connects to the mail server at example.com and sends your local
computer's host name in the HELO / EHLO command.
smtp://mail.example.com/client.example.com - This will send client.example.com in the HELO /
EHLO command to the mail server at example.com.
POP3
The path part of a POP3 request specifies the message ID to retrieve. If the ID is not speci-fied specified
fied then a list of waiting messages is returned instead.
pop3://user:password@mail.example.com - This lists the available messages for the user
pop3://user:password@mail.example.com/1 - This retrieves the first message for the user
IMAP
The path part of an IMAP request not only specifies the mailbox to list (Added in 7.30.0) or
select, but can also be used to check the UIDVALIDITY of the mailbox and to specify the UID
and SECTION of the message to fetch (Added in 7.30.0).
imap://user:password@mail.example.com - Performs a top level folder list
imap://user:password@mail.example.com/INBOX - Performs a folder list on the user's inbox
imap://user:password@mail.example.com/INBOX/;UID=1 - Selects the user's inbox and fetches mes-sage message
sage 1
imap://user:password@mail.example.com/INBOX;UIDVALIDITY=50/;UID=2 - Selects the user's inbox,
checks the UIDVALIDITY of the mailbox is 50 and fetches message 2 if it is
imap://user:password@mail.example.com/INBOX/;UID=3/;SECTION=TEXT - Selects the user's inbox
and fetches message 3 with only the text portion of the message
For more information about the individual components of an IMAP URL please see RFC5092.
SCP
The path part of a SCP request specifies the file to retrieve and from what directory. The
file part may not be omitted. The file is taken as an absolute path from the root directory on
the server. To specify a path relative to the user's home directory on the server, prepend ~/
to the path portion. If the user name is not embedded in the URL, it can be set with the CUR-LOPT_USERPWD CURLOPT_USERPWD
LOPT_USERPWD or CURLOPT_USERNAME option.
scp://user@example.com/etc/issue - This specifies the file /etc/issue
scp://example.com/~/my-file - This specifies the file my-file in the user's home directory on
the server
SFTP
The path part of a SFTP request specifies the file to retrieve and from what directory. If the
file part is omitted then libcurl downloads the directory listing for the directory specified.
If the path ends in a / then a directory listing is returned instead of a file. If the path
is omitted entirely then the directory listing for the root / home directory will be returned.
If the user name is not embedded in the URL, it can be set with the CURLOPT_USERPWD or CUR-LOPT_USERNAME CURLOPT_USERNAME
LOPT_USERNAME option.
sftp://user:password@example.com/etc/issue - This specifies the file /etc/issue
sftp://user@example.com/~/my-file - This specifies the file my-file in the user's home direc-tory directory
tory
sftp://ssh.example.com/~/Documents/ - This requests a directory listing of the Documents
directory under the user's home directory
LDAP
The path part of a LDAP request can be used to specify the: Distinguished Name, Attributes,
Scope, Filter and Extension for a LDAP search. Each field is separated by a question mark and
when that field is not required an empty string with the question mark separator should be
included.
ldap://ldap.example.com/o=My%20Organisation - This will perform a LDAP search with the DN as
My Organisation.
ldap://ldap.example.com/o=My%20Organisation?postalAddress - This will perform the same search
but will only return postalAddress attributes.
ldap://ldap.example.com/?rootDomainNamingContext - This specifies an empty DN and requests
information about the rootDomainNamingContext attribute for an Active Directory server.
For more information about the individual components of a LDAP URL please see RFC4516.
NOTES
Starting with version 7.20.0, the fragment part of the URI will not be sent as part of the
path, which was previously the case.
CURLOPT_URL is the only option that must be set before curl_easy_perform(3) is called.
CURLOPT_PROTOCOLS can be used to limit what protocols libcurl will use for this transfer,
independent of what libcurl has been compiled to support. That may be useful if you accept the
URL from an external source and want to limit the accessibility.
CURLOPT_PROTOCOLS
Pass a long that holds a bitmask of CURLPROTO_* defines. If used, this bitmask limits what
protocols libcurl may use in the transfer. This allows you to have a libcurl built to support
a wide range of protocols but still limit specific transfers to only be allowed to use a sub-set subset
set of them. By default libcurl will accept all protocols it supports. See also CUR-LOPT_REDIR_PROTOCOLS. CURLOPT_REDIR_PROTOCOLS.
LOPT_REDIR_PROTOCOLS. (Added in 7.19.4)
CURLOPT_REDIR_PROTOCOLS
Pass a long that holds a bitmask of CURLPROTO_* defines. If used, this bitmask limits what
protocols libcurl may use in a transfer that it follows to in a redirect when CURLOPT_FOL-LOWLOCATION CURLOPT_FOLLOWLOCATION
LOWLOCATION is enabled. This allows you to limit specific transfers to only be allowed to use
a subset of protocols in redirections. By default libcurl will allow all protocols except for
FILE and SCP. This is a difference compared to pre-7.19.4 versions which unconditionally would
follow to all protocols supported. (Added in 7.19.4)
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. If not specified, libcurl will default to using port 1080 for proxies. CURLOPT_PROXY-PORT. CURLOPT_PROXYPORT.
PORT.
When you tell the library to use a HTTP proxy, libcurl will transparently convert operations
to HTTP even if you specify an 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_HTTPPROXY-TUNNEL. CURLOPT_HTTPPROXYTUNNEL.
TUNNEL.
libcurl respects the environment variables http_proxy, ftp_proxy, all_proxy etc, if any of
those are set. The CURLOPT_PROXY option does however override any possibly set environment
variables.
Setting the proxy string to "" (an empty string) will explicitly disable the use of a proxy,
even if there is an environment variable set for it.
Since 7.14.1, the proxy host string given in environment variables can be specified the exact
same way as the proxy can be set with CURLOPT_PROXY, include protocol prefix (http://) and
embedded user + password.
Since 7.21.7, the proxy string may be specified with a protocol:// prefix to specify alterna-tive alternative
tive proxy protocols. Use socks4://, socks4a://, socks5:// or socks5h:// (the last one to
enable socks5 and asking the proxy to do the resolving, also known as CURLPROXY_SOCKS5_HOST-NAME CURLPROXY_SOCKS5_HOSTNAME
NAME type) to request the specific SOCKS version to be used. No protocol specified, http://
и all others will be treated as HTTP proxies.
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 CURL-PROXY_HTTP, CURLPROXY_HTTP,
PROXY_HTTP, CURLPROXY_HTTP_1__ (added in 7.19.4), CURLPROXY_SOCKS4 (added in 7.10), CURL-PROXY_SOCKS5, CURLPROXY_SOCKS5,
PROXY_SOCKS5, CURLPROXY_SOCKS4A (added in 7.18.0) and CURLPROXY_SOCKS5_HOSTNAME (added in
7.18.0). The HTTP type is default. (Added in 7.10)
If you set CURLOPT_PROXYTYPE to CURLPROXY_HTTP_1__, it will only affect how libcurl speaks to
a proxy when CONNECT is used. The HTTP version used for "regular" HTTP requests is instead
controlled with CURLOPT_HTTP_VERSION.
CURLOPT_NOPROXY
Pass a pointer to a zero terminated string. The string consists of a comma separated list of
host names that do not require a proxy to get reached, even if one is specified. The only
wildcard available is a single * character, which matches all hosts, and effectively disables
the proxy. Each name in this list is matched as either a domain which contains the hostname,
or the hostname itself. For example, example.com would match example.com, example.com:80, and
www.example.com, but not www.notanexample.com. (Added in 7.19.4)
CURLOPT_HTTPPROXYTUNNEL
Set the parameter to 1 to make the library tunnel all operations through a given HTTP proxy.
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.
CURLOPT_SOCKS5_GSSAPI_SERVICE
Pass a char * as parameter to a string holding the name of the service. The default service
name for a SOCKS5 server is rcmd/server-fqdn. This option allows you to change it. (Added in
7.19.4)
CURLOPT_SOCKS5_GSSAPI_NEC
Pass a long set to 1 to enable or 0 to disable. As part of the gssapi negotiation a protection
mode is negotiated. The RFC1961 says in section 4.3/4.4 it should be protected, but the NEC
reference implementation does not. If enabled, this option allows the unprotected exchange of
the protection mode negotiation. (Added in 7.19.4).
CURLOPT_INTERFACE
Pass a char * as parameter. This sets the interface name to use as outgoing network interface.
The name can be an interface name, an IP address, or a host name.
Starting with 7.24.0: If the parameter starts with "if!" then it is treated as only as inter-face interface
face name and no attempt will ever be named to do treat it as an IP address or to do name res-olution resolution
olution on it. If the parameter starts with "host!" it is treated as either an IP address or
a hostname. Hostnames are resolved synchronously. Using the if! format is highly recommended
when using the multi interfaces to avoid allowing the code to block. If "if!" is specified
but the parameter does not match an existing interface, CURLE_INTERFACE_FAILED is returned.
CURLOPT_LOCALPORT
Pass a long. This sets the local port number of the socket used for connection. This can be
used in combination with CURLOPT_INTERFACE and you are recommended to use CURLOPT_LOCALPOR-TRANGE CURLOPT_LOCALPORTRANGE
TRANGE as well when this is set. Valid port numbers are 1 - 65535. (Added in 7.15.2)
CURLOPT_LOCALPORTRANGE
Pass a long. This is the number of attempts libcurl will make to find a working local port
number. It starts with the given CURLOPT_LOCALPORT and adds one to the number for each retry.
Setting this to 1 or below will make libcurl do only one try for the exact port number. Port
numbers by nature are scarce resources that will be busy at times so setting this value to
something too low might cause unnecessary connection setup failures. (Added in 7.15.2)
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 to completely disable caching, or set to -1 to make the cached
entries remain forever. By default, libcurl caches this info for 60 seconds.
The name resolve functions of various libc implementations don't re-read name server informa-tion information
tion unless explicitly told so (for example, by calling res_init(3)). This may cause libcurl
to keep using the older server even if DHCP has updated the server info, and this may look
like a DNS cache issue to the casual libcurl-app user.
CURLOPT_DNS_USE_GLOBAL_CACHE
Pass a long. If the value is 1, 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 variable.
WARNING: this option is considered obsolete. Stop using it. Switch over to using the share
interface instead! See CURLOPT_SHARE and curl_share_init(3).
CURLOPT_BUFFERSIZE
Pass a long specifying your preferred size (in bytes) 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)
This size is by default set as big as possible (CURL_MAX_WRITE_SIZE), so it only makes sense
to use this option if you want it smaller.
CURLOPT_PORT
Pass a long specifying what remote port number to connect to, instead of the one specified in
the URL or the default port for the used protocol.
CURLOPT_TCP_NODELAY
Pass a long specifying whether the TCP_NODELAY option is to be set or cleared (1 = set, 0 =
clear). The option is cleared by default. This will have no effect after the connection has
been established.
Setting this option will disable TCP's Nagle algorithm. The purpose of this algorithm is to
try to minimize the number of small packets on the network (where "small packets" means TCP
segments less than the Maximum Segment Size (MSS) for the network).
Maximizing the amount of data sent per TCP segment is good because it amortizes the overhead
of the send. However, in some cases (most notably telnet or rlogin) small segments may need to
be sent without delay. This is less efficient than sending larger amounts of data at a time,
and can contribute to congestion on the network if overdone.
CURLOPT_ADDRESS_SCOPE
Pass a long specifying the scope_id value to use when connecting to IPv6 link-local or site-local sitelocal
local addresses. (Added in 7.19.0)
CURLOPT_TCP_KEEPALIVE
Pass a long. If set to 1, TCP keepalive probes will be sent. The delay and frequency of these
probes can be controlled by the CURLOPT_TCP_KEEPIDLE and CURLOPT_TCP_KEEPINTVL options, pro-vided provided
vided the operating system supports them. Set to 0 (default behavior) to disable keepalive
probes (Added in 7.25.0).
CURLOPT_TCP_KEEPIDLE
Pass a long. Sets the delay, in seconds, that the operating system will wait while the connec-tion connection
tion is idle before sending keepalive probes. Not all operating systems support this option.
(Added in 7.25.0)
CURLOPT_TCP_KEEPINTVL
Pass a long. Sets the interval, in seconds, that the operating system will wait between send-ing sending
ing keepalive probes. Not all operating systems support this option. (Added in 7.25.0)
NAMES and PASSWORDS OPTIONS (Authentication)
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.
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 pre-ferred. preferred.
ferred. The file will be scanned for the host and user name (to find the password
only) or for 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 informa-tion information
tion in the URL, and to search the file for the host only.
Only machine name, user name and password are taken into account (init macros and similar things
aren't supported).
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_NETRC_FILE
Pass a char * as parameter, pointing to a zero terminated string containing the full path name
to the file you want libcurl to use as .netrc file. If this option is omitted, and CUR-LOPT_NETRC CURLOPT_NETRC
LOPT_NETRC is set, libcurl will attempt to find a .netrc file in the current user's home
directory. (Added in 7.10.9)
CURLOPT_USERPWD
Pass a char * as parameter, which should be [user name]:[password] to use for the connection.
Use CURLOPT_HTTPAUTH to decide the authentication method.
When using NTLM, you can set the domain by prepending it to the user name and separating the
domain and name with a forward (/) or backward slash (\). Like this: "domain/user:password" or
"domain\user:password". Some HTTP servers (on Windows) support this style even for Basic
authentication.
When using HTTP and CURLOPT_FOLLOWLOCATION, libcurl might perform several requests to possibly
different hosts. libcurl will only send this user and password information to hosts using the
initial host name (unless CURLOPT_UNRESTRICTED_AUTH is set), so if libcurl follows locations
to other hosts it will not send the user and password to those. This is enforced to prevent
accidental information leakage.
CURLOPT_PROXYUSERPWD
Pass a char * as parameter, which should be [user name]:[password] to use for the connection
to the HTTP proxy. Use CURLOPT_PROXYAUTH to decide the authentication method.
CURLOPT_USERNAME
Pass a char * as parameter, which should be pointing to the zero terminated user name to use
for the transfer.
CURLOPT_USERNAME sets the user name to be used in protocol authentication. You should not use
this option together with the (older) CURLOPT_USERPWD option.
In order to specify the password to be used in conjunction with the user name use the CUR-LOPT_PASSWORD CURLOPT_PASSWORD
LOPT_PASSWORD option. (Added in 7.19.1)
CURLOPT_PASSWORD
Pass a char * as parameter, which should be pointing to the zero terminated password to use
for the transfer.
The CURLOPT_PASSWORD option should be used in conjunction with the CURLOPT_USERNAME option.
(Added in 7.19.1)
CURLOPT_PROXYUSERNAME
Pass a char * as parameter, which should be pointing to the zero terminated user name to use
for the transfer while connecting to Proxy.
The CURLOPT_PROXYUSERNAME option should be used in same way as the CURLOPT_PROXYUSERPWD is
used. In comparison to CURLOPT_PROXYUSERPWD the CURLOPT_PROXYUSERNAME allows the username to
contain a colon, like in the following example: "sip:user@example.com". The CURLOPT_PROXYUSER-NAME CURLOPT_PROXYUSERNAME
NAME option is an alternative way to set the user name while connecting to Proxy. There is no
meaning to use it together with the CURLOPT_PROXYUSERPWD option.
In order to specify the password to be used in conjunction with the user name use the CUR-LOPT_PROXYPASSWORD CURLOPT_PROXYPASSWORD
LOPT_PROXYPASSWORD option. (Added in 7.19.1)
CURLOPT_PROXYPASSWORD
Pass a char * as parameter, which should be pointing to the zero terminated password to use
for the transfer while connecting to Proxy.
The CURLOPT_PROXYPASSWORD option should be used in conjunction with the CURLOPT_PROXYUSERNAME
option. (Added in 7.19.1)
CURLOPT_HTTPAUTH
Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication
method(s) you want it to use. The available bits are listed below. If more than one bit is
set, libcurl will first query the site to see which authentication methods it supports and
then pick the best one you allow it to use. For some methods, this will induce an extra net-work network
work round-trip. Set the actual name and password with the CURLOPT_USERPWD option or with the
CURLOPT_USERNAME and the CURLOPT_PASSWORD options. (Added in 7.10.6)
CURLAUTH_BASIC
HTTP Basic authentication. This is the default choice, and the only method that is in
wide-spread use and supported virtually everywhere. This sends the user name and pass-word password
word over the network in plain text, easily captured by others.
CURLAUTH_DIGEST
HTTP Digest authentication. Digest authentication is defined in RFC2617 and is a more
secure way to do authentication over public networks than the regular old-fashioned
Basic method.
CURLAUTH_DIGEST_IE
HTTP Digest authentication with an IE flavor. Digest authentication is defined in
RFC2617 and is a more secure way to do authentication over public networks than the
regular old-fashioned Basic method. The IE flavor is simply that libcurl will use a
special "quirk" that IE is known to have used before version 7 and that some servers
require the client to use. (This define was added in 7.19.3)
CURLAUTH_GSSNEGOTIATE
HTTP GSS-Negotiate authentication. The GSS-Negotiate (also known as plain "Negotiate")
method was designed by Microsoft and is used in their web applications. It is primarily
meant as a support for Kerberos5 authentication but may also be used along with other
authentication methods. For more information see IETF draft draft-brezak-spnego-http-04.txt. draft-brezak-spnegohttp-04.txt.
http-04.txt.
You need to build libcurl with a suitable GSS-API library for this to work.
CURLAUTH_NTLM
HTTP NTLM authentication. A proprietary protocol invented and used by Microsoft. It
uses a challenge-response and hash concept similar to Digest, to prevent the password
from being eavesdropped.
You need to build libcurl with either OpenSSL, GnuTLS or NSS support for this option to
work, or build libcurl on Windows.
CURLAUTH_NTLM_WB
NTLM delegating to winbind helper. Authentication is performed by a separate binary
application that is executed when needed. The name of the application is specified at
compile time but is typically /usr/bin/ntlm_auth (Added in 7.22.0)
Note that libcurl will fork when necessary to run the winbind application and kill it
when complete, calling waitpid() to await its exit when done. On POSIX operating sys-tems, systems,
tems, killing the process will cause a SIGCHLD signal to be raised (regardless of
whether CURLOPT_NOSIGNAL is set), which must be handled intelligently by the applica-tion. application.
tion. In particular, the application must not unconditionally call wait() in its
SIGCHLD signal handler to avoid being subject to a race condition. This behavior is
subject to change in future versions of libcurl.
CURLAUTH_ANY
This is a convenience macro that sets all bits and thus makes libcurl pick any it finds
suitable. libcurl will automatically select the one it finds most secure.
CURLAUTH_ANYSAFE
This is a convenience macro that sets all bits except Basic and thus makes libcurl pick
any it finds suitable. libcurl will automatically select the one it finds most secure.
CURLAUTH_ONLY
This is a meta symbol. Or this value together with a single specific auth value to
force libcurl to probe for un-restricted auth and if not, only that single auth algo-rithm algorithm
rithm is acceptable. (Added in 7.21.3)
CURLOPT_TLSAUTH_TYPE
Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication
method(s) you want it to use for TLS authentication.
CURLOPT_TLSAUTH_SRP
TLS-SRP authentication. Secure Remote Password authentication for TLS is defined in
RFC5054 and provides mutual authentication if both sides have a shared secret. To use
TLS-SRP, you must also set the CURLOPT_TLSAUTH_USERNAME and CURLOPT_TLSAUTH_PASSWORD
options.
You need to build libcurl with GnuTLS or OpenSSL with TLS-SRP support for this to work.
(Added in 7.21.4)
CURLOPT_TLSAUTH_USERNAME
Pass a char * as parameter, which should point to the zero terminated username to use for the
TLS authentication method specified with the CURLOPT_TLSAUTH_TYPE option. Requires that the
CURLOPT_TLS_PASSWORD option also be set. (Added in 7.21.4)
CURLOPT_TLSAUTH_PASSWORD
Pass a char * as parameter, which should point to the zero terminated password to use for the
TLS authentication method specified with the CURLOPT_TLSAUTH_TYPE option. Requires that the
CURLOPT_TLS_USERNAME option also be set. (Added in 7.21.4)
CURLOPT_PROXYAUTH
Pass a long as parameter, which is set to a bitmask, to tell libcurl which authentication
method(s) you want it to use for your proxy authentication. If more than one bit is set,
libcurl will first query the site to see what authentication methods it supports and then pick
the best one you allow it to use. For some methods, this will induce an extra network round-trip. roundtrip.
trip. Set the actual name and password with the CURLOPT_PROXYUSERPWD option. The bitmask can
be constructed by or'ing together the bits listed above for the CURLOPT_HTTPAUTH option. As of
this writing, only Basic, Digest and NTLM work. (Added in 7.10.7)
HTTP OPTIONS
CURLOPT_AUTOREFERER
Pass a parameter set to 1 to enable this. When enabled, libcurl will automatically set the
Referer: field in requests where it follows a Location: redirect.
CURLOPT_ACCEPT_ENCODING
Sets the contents of the Accept-Encoding: header sent in a HTTP request, and enables decoding
of a response when a Content-Encoding: header is received. Three encodings are supported:
identity, which does nothing, deflate which requests the server to compress its response using
the zlib algorithm, and gzip which requests the gzip algorithm. If a zero-length string is
set, then an Accept-Encoding: header containing all supported encodings is sent.
This is a request, not an order; the server may or may not do it. This option must be set (to
any non-NULL value) or else any unsolicited encoding done by the server is ignored. See the
special file lib/README.encoding for details.
(This option was called CURLOPT_ENCODING before 7.21.6)
CURLOPT_TRANSFER_ENCODING
Adds a request for compressed Transfer Encoding in the outgoing HTTP request. If the server
supports this and so desires, it can respond with the HTTP response sent using a compressed
Transfer-Encoding that will be automatically uncompressed by libcurl on reception.
Transfer-Encoding differs slightly from the Content-Encoding you ask for with CUR-LOPT_ACCEPT_ENCODING CURLOPT_ACCEPT_ENCODING
LOPT_ACCEPT_ENCODING in that a Transfer-Encoding is strictly meant to be for the transfer and
thus MUST be decoded before the data arrives in the client. Traditionally, Transfer-Encoding
has been much less used and supported by both HTTP clients and HTTP servers.
(Added in 7.21.6)
CURLOPT_FOLLOWLOCATION
A parameter set to 1 tells the library to follow any Location: header that the server sends as
part of a HTTP header.
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.
Since 7.19.4, libcurl can limit what protocols it will automatically follow. The accepted pro-tocols protocols
tocols are set with CURLOPT_REDIR_PROTOCOLS and it excludes the FILE protocol by default.
CURLOPT_UNRESTRICTED_AUTH
A parameter set to 1 tells the library it can continue to send authentication (user+password)
when following locations, even when hostname changed. This option is meaningful only when set-ting setting
ting CURLOPT_FOLLOWLOCATION.
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 7.15.1: Setting
the limit to 0 will make libcurl refuse any redirect. Set it to -1 for an infinite number of
redirects (which is the default)
CURLOPT_POSTREDIR
Pass a bitmask to control how libcurl acts on redirects after POSTs that get a 301, 302 or 303
response back. A parameter with bit 0 set (value CURL_REDIR_POST_301) tells the library to
respect RFC2616/10.3.2 and not convert POST requests into GET requests when following a 301
redirection. Setting bit 1 (value CURL_REDIR_POST_302) makes libcurl maintain the request
method after a 302 redirect whilst setting bit 2 (value CURL_REDIR_POST_303) makes libcurl
maintain the request method after a 303 redirect. The value CURL_REDIR_POST_ALL is a conve-nience convenience
nience define that sets all three bits.
The non-RFC behaviour is ubiquitous in web browsers, so the library does the conversion by
default to maintain consistency. However, a server may require a POST to remain a POST after
such a redirection. This option is meaningful only when setting CURLOPT_FOLLOWLOCATION.
(Added in 7.17.1) (This option was known as CURLOPT_POST301 up to 7.19.0 as it only supported
the 301 then)
CURLOPT_PUT
A parameter set to 1 tells the library to use HTTP PUT to transfer data. The data should be
set with CURLOPT_READDATA and CURLOPT_INFILESIZE.
This option is deprecated and starting with version 7.12.1 you should instead use CUR-LOPT_UPLOAD. CURLOPT_UPLOAD.
LOPT_UPLOAD.
CURLOPT_POST
A parameter set to 1 tells the library to do a regular HTTP post. This will also make the
library use a "Content-Type: application/x-www-form-urlencoded" header. (This is by far the
most commonly used POST method).
Use one of CURLOPT_POSTFIELDS or CURLOPT_COPYPOSTFIELDS options to specify what data to post
and CURLOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE to set the data size.
Optionally, you can provide data to POST using the CURLOPT_READFUNCTION and CURLOPT_READDATA
options but then you must make sure to not set CURLOPT_POSTFIELDS to anything but NULL. When
providing data with a callback, you must transmit it using chunked transfer-encoding or you
must set the size of the data with the CURLOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE
option. To enable chunked encoding, you simply pass in the appropriate Transfer-Encoding
header, see the post-callback.c example.
You can override the default POST Content-Type: header by setting your own with CURLOPT_HTTP-HEADER. CURLOPT_HTTPHEADER.
HEADER.
Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
If you use POST to a HTTP 1.1 server, you can send data without knowing the size before start-ing starting
ing the POST if you use chunked encoding. You enable this by adding a header like "Transfer-Encoding: "TransferEncoding:
Encoding: chunked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked transfer, you
must specify the size in the request.
When setting CURLOPT_POST to 1, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).
If you issue a POST request and then want to make a HEAD or GET using the same re-used handle,
you must explicitly set the new request type using CURLOPT_NOBODY or CURLOPT_HTTPGET or simi-lar. similar.
lar.
CURLOPT_POSTFIELDS
Pass a void * as parameter, which should be the full data to post in a HTTP POST operation.
You must make sure that the data is formatted the way you want the server to receive it.
libcurl will not convert or encode it for you. Most web servers will assume this data to be
url-encoded.
The pointed data are NOT copied by the library: as a consequence, they must be preserved by
the calling application until the transfer finishes.
This POST is a normal application/x-www-form-urlencoded kind (and libcurl will set that Con-tent-Type Content-Type
tent-Type by default when this option is used), which is the most commonly used one by HTML
forms. See also the CURLOPT_POST. Using CURLOPT_POSTFIELDS implies CURLOPT_POST.
If you want to do a zero-byte POST, you need to set CURLOPT_POSTFIELDSIZE explicitly to zero,
as simply setting CURLOPT_POSTFIELDS to NULL or "" just effectively disables the sending of
the specified string. libcurl will instead assume that you'll send the POST data using the
read callback!
Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
To make multipart/formdata posts (aka RFC2388-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 -1, the library will use strlen() to
get the size.
CURLOPT_POSTFIELDSIZE_LARGE
Pass a curl_off_t as parameter. Use this to set the size of the CURLOPT_POSTFIELDS data to
prevent libcurl from doing strlen() on the data to figure out the size. This is the large file
version of the CURLOPT_POSTFIELDSIZE option. (Added in 7.11.1)
CURLOPT_COPYPOSTFIELDS
Pass a char * as parameter, which should be the full data to post in a HTTP POST operation. It
behaves as the CURLOPT_POSTFIELDS option, but the original data are copied by the library,
allowing the application to overwrite the original data after setting this option.
Because data are copied, care must be taken when using this option in conjunction with CUR-LOPT_POSTFIELDSIZE CURLOPT_POSTFIELDSIZE
LOPT_POSTFIELDSIZE or CURLOPT_POSTFIELDSIZE_LARGE: If the size has not been set prior to CUR-LOPT_COPYPOSTFIELDS, CURLOPT_COPYPOSTFIELDS,
LOPT_COPYPOSTFIELDS, the data are assumed to be a NUL-terminated string; else the stored size
informs the library about the data byte count to copy. In any case, the size must not be
changed after CURLOPT_COPYPOSTFIELDS, unless another CURLOPT_POSTFIELDS or CURLOPT_COPYPOST-FIELDS CURLOPT_COPYPOSTFIELDS
FIELDS option is issued. (Added in 7.17.1)
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 curl_httppost structs as parameter.
The easiest way to create such a list, 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).
Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
When setting CURLOPT_HTTPPOST, it will automatically set CURLOPT_NOBODY to 0 (since 7.14.1).
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: UserAgent:
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 content 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. To
add a header with no content, make the content be two quotes: "". The headers included in the
linked list must not be CRLF-terminated, because curl adds CRLF after each header item. Fail-ure Failure
ure to comply with this will result in strange bugs because the server will most likely ignore
part of the headers you specified.
The first line in a request (containing the method, usually a GET or POST) is not a header and
cannot be replaced using this option. Only the lines following the request-line are headers.
Adding this method line in this list of headers will only cause your request to send an
invalid header.
Pass a NULL to this to reset back to no custom headers.
The most commonly replaced headers have "shortcuts" in the options CURLOPT_COOKIE, CUR-LOPT_USERAGENT CURLOPT_USERAGENT
LOPT_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.
The alias itself is not parsed for any version strings. Before libcurl 7.16.3, Libcurl used
the value set by option CURLOPT_HTTP_VERSION, but starting with 7.16.3 the protocol is assumed
to match HTTP 1.0 when an alias matched.
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 multiple cookies, you need to set them all using a single option and thus
you need to concatenate them all in one single string. Set multiple cookies in one string like
this: "name1=content1; name2=content2;" etc.
This option sets the cookie header explicitly in the outgoing request(s). If multiple requests
are done due to authentication, followed redirections or similar, they will all get this
cookie passed on.
Using this option multiple times will only make the latest string override the previous 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 or by passing the empty string (""), this option will
enable cookies for this curl handle, making it understand and parse received cookies and then
use matching cookies in future requests.
If you use this option multiple times, you just add more files to read. Subsequent files will
add more cookies.
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.
If the cookie jar file can't be created or written to (when the curl_easy_cleanup(3) is
called), libcurl will not and cannot report an error for this. Using CURLOPT_VERBOSE or CUR-LOPT_DEBUGFUNCTION CURLOPT_DEBUGFUNCTION
LOPT_DEBUGFUNCTION will get a warning to display, but that is the only visible feedback you
get about this possibly lethal situation.
CURLOPT_COOKIESESSION
Pass a long set to 1 to mark this as a new cookie "session". It will force libcurl to ignore
all cookies it is about to load that are "session cookies" from the previous session. By
default, libcurl always stores and loads all cookies, independent if they are session cookies
or not. Session cookies are cookies without expiry date and they are meant to be alive and
existing for this "session" only.
CURLOPT_COOKIELIST
Pass a char * to a cookie string. Cookie can be either in Netscape / Mozilla format or just
regular HTTP-style header (Set-Cookie: ...) format. If cURL cookie engine was not enabled it
will enable its cookie engine. Passing a magic string "ALL" will erase all cookies known by
cURL. (Added in 7.14.1) Passing the special string "SESS" will only erase all session cookies
known by cURL. (Added in 7.15.4) Passing the special string "FLUSH" will write all cookies
known by cURL to the file specified by CURLOPT_COOKIEJAR. (Added in 7.17.1)
CURLOPT_HTTPGET
Pass a long. If the long is 1, this forces the HTTP request to get back to GET. Usable if a
POST, HEAD, PUT, or a custom request has been used previously using the same curl handle.
When setting CURLOPT_HTTPGET to 1, it will automatically set CURLOPT_NOBODY to 0 and CUR-LOPT_UPLOAD CURLOPT_UPLOAD
LOPT_UPLOAD to 0.
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.
CURLOPT_IGNORE_CONTENT_LENGTH
Ignore the Content-Length header. This is useful for Apache 1.x (and similar servers) which
will report incorrect content length for files over 2 gigabytes. If this option is used, curl
will not be able to accurately report progress, and will simply stop the download when the
server ends the connection. (added in 7.14.1)
CURLOPT_HTTP_CONTENT_DECODING
Pass a long to tell libcurl how to act on content decoding. If set to zero, content decoding
will be disabled. If set to 1 it is enabled. Libcurl has no default content decoding but
requires you to use CURLOPT_ACCEPT_ENCODING for that. (added in 7.16.2)
CURLOPT_HTTP_TRANSFER_DECODING
Pass a long to tell libcurl how to act on transfer decoding. If set to zero, transfer decoding
will be disabled, if set to 1 it is enabled (default). libcurl does chunked transfer decoding
by default unless this option is set to zero. (added in 7.16.2)
SMTP OPTIONS
CURLOPT_MAIL_FROM
Pass a pointer to a zero terminated string as parameter. This should be used to specify the
sender's email address when sending SMTP mail with libcurl.
An originator email address should be specified with angled brackets (<>) around it, which if
not specified, will be added by libcurl from version 7.21.4 onwards. Failing to provide such
brackets may cause the server to reject the email.
If this parameter is not specified then an empty address will be sent to the mail server which
may or may not cause the email to be rejected.
(Added in 7.20.0)
CURLOPT_MAIL_RCPT
Pass a pointer to a linked list of recipients to pass to the server in your SMTP mail 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.
Each recipient should be specified within a pair of angled brackets (<>), however, should you
not use an angled bracket as the first character libcurl will assume you provided a single
email address and enclose that address within brackets for you.
(Added in 7.20.0)
CURLOPT_MAIL_AUTH
Pass a pointer to a zero terminated string as parameter. This will be used to specify the
authentication address (identity) of a submitted message that is being relayed to another
server.
This optional parameter allows co-operating agents in a trusted environment to communicate the
authentication of individual messages and should only be used by the application program,
using libcurl, if the application is itself a mail server acting in such an environment. If
the application is operating as such and the AUTH address is not known or is invalid, then an
empty string should be used for this parameter.
Unlike CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT, the address should not be specified within a
pair of angled brackets (<>). However, if an empty string is used then a pair of brackets will
be sent by libcurl as required by RFC2554.
(Added in 7.25.0)
TFTP OPTIONS
CURLOPT_TFTP_BLKSIZE
Specify block size to use for TFTP data transmission. Valid range as per RFC2348 is 8-65464
bytes. The default of 512 bytes will be used if this option is not specified. The specified
block size will only be used pending support by the remote server. If the server does not
return an option acknowledgement or returns an option acknowledgement with no blksize, the
default of 512 bytes will be used. (added in 7.19.4)
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, a network
interface name (under Unix) or just a '-' symbol to let the library use your system's default
IP address. Default FTP operations are passive, and thus won't use PORT.
The address can be followed by a ':' to specify a port, optionally followed by a '-' to spec-ify specify
ify a port range. If the port specified is 0, the operating system will pick a free port. If
a range is provided and all ports in the range are not available, libcurl will report
CURLE_FTP_PORT_FAILED for the handle. Invalid port/range settings are ignored. IPv6
addresses followed by a port or portrange have to be in brackets. IPv6 addresses without
port/range specifier can be in brackets. (added in 7.19.5)
Examples with specified ports:
eth0:0
192.168.1.2:32000-33000
curl.se:32123
[::1]:1234-4567
You disable PORT again and go back to using the passive version by setting this option to
NULL.
CURLOPT_QUOTE
Pass a pointer to a linked list of FTP or SFTP commands to pass to the server prior to your
FTP request. This will be done before any other commands are issued (even before the CWD com-mand command
mand for FTP). The linked list should be a fully valid list of 'struct curl_slist' structs
properly filled in with text strings. Use curl_slist_append(3) to append strings (commands) to
the list, and clear the entire list afterwards with curl_slist_free_all(3). Disable this oper-ation operation
ation again by setting a NULL to this option. When speaking to a FTP (or SFTP since 7.24.0)
server, prefix the command with an asterisk (*) to make libcurl continue even if the command
fails as by default libcurl will stop at first failure.
The set of valid FTP commands depends on the server (see RFC959 for a list of mandatory com-mands). commands).
mands).
The valid SFTP commands are: chgrp, chmod, chown, ln, mkdir, pwd, rename, rm, rmdir, symlink
(see curl(1)) (SFTP support added in 7.16.3)
CURLOPT_POSTQUOTE
Pass a pointer to a linked list of FTP or SFTP commands to pass to the server after your FTP
transfer request. The commands will only be run if no error occurred. The linked list should
be a fully valid list of struct curl_slist structs properly filled in as described for CUR-LOPT_QUOTE. CURLOPT_QUOTE.
LOPT_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. Before version 7.16.0, if you also set CURLOPT_NOBODY to 1, this option didn't
work.
CURLOPT_DIRLISTONLY
A parameter set to 1 tells the library to just list the names of files in a directory, instead
of doing a full directory listing that would include file sizes, dates etc. This works for FTP
and SFTP URLs.
This causes an FTP NLST command to be sent on an FTP server. Beware that some FTP servers
list only files in their response to NLST; they might not include subdirectories and symbolic
links.
Setting this option to 1 also implies a directory listing even if the URL doesn't end with a
slash, which otherwise is necessary.
Do NOT use this option if you also use CURLOPT_WILDCARDMATCH as it will effectively break that
feature then.
(This option was known as CURLOPT_FTPLISTONLY up to 7.16.4)
CURLOPT_APPEND
A parameter set to 1 tells the library to append to the remote file instead of overwrite it.
This is only useful when uploading to an FTP site.
(This option was known as CURLOPT_FTPAPPEND up to 7.16.4)
CURLOPT_FTP_USE_EPRT
Pass a long. If the value is 1, it tells curl to use the EPRT (and LPRT) command when doing
active FTP downloads (which is enabled by CURLOPT_FTPPORT). Using EPRT means that it will
first attempt to use EPRT and then LPRT before using PORT, but if you pass zero to this
option, it will not try using EPRT or LPRT, only plain PORT. (Added in 7.10.5)
If the server is an IPv6 host, this option will have no effect as of 7.12.3.
CURLOPT_FTP_USE_EPSV
Pass a long. If the value is 1, 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 zero to this option, it will not try using EPSV,
only plain PASV.
If the server is an IPv6 host, this option will have no effect as of 7.12.3.
CURLOPT_FTP_USE_PRET
Pass a long. If the value is 1, it tells curl to send a PRET command before PASV (and EPSV).
Certain FTP servers, mainly drftpd, require this non-standard command for directory listings
as well as up and downloads in PASV mode. Has no effect when using the active FTP transfers
mode. (Added in 7.20.0)
CURLOPT_FTP_CREATE_MISSING_DIRS
Pass a long. If the value is 1, curl will attempt to create any remote directory that it fails
to CWD into. CWD is the command that changes working directory. (Added in 7.10.7)
This setting also applies to SFTP-connections. curl will attempt to create the remote direc-tory directory
tory if it can't obtain a handle to the target-location. The creation will fail if a file of
the same name as the directory to create already exists or lack of permissions prevents cre-ation. creation.
ation. (Added in 7.16.3)
Starting with 7.19.4, you can also set this value to 2, which will make libcurl retry the CWD
command again if the subsequent MKD command fails. This is especially useful if you're doing
many simultaneous connections against the same server and they all have this option enabled,
as then CWD may first fail but then another connection does MKD before this connection and
thus MKD fails but trying CWD works! 7.19.4 also introduced the CURLFTP_CREATE_DIR and
CURLFTP_CREATE_DIR_RETRY enum names for these arguments.
Before version 7.19.4, libcurl will simply ignore arguments set to 2 and act as if 1 was
selected.
CURLOPT_FTP_RESPONSE_TIMEOUT
Pass a long. Causes curl to set a timeout period (in seconds) on the amount of time that the
server is allowed to take in order to generate a response message for a command before the
session is considered hung. While curl is waiting for a response, this value overrides CUR-LOPT_TIMEOUT. CURLOPT_TIMEOUT.
LOPT_TIMEOUT. It is recommended that if used in conjunction with CURLOPT_TIMEOUT, you set CUR-LOPT_FTP_RESPONSE_TIMEOUT CURLOPT_FTP_RESPONSE_TIMEOUT
LOPT_FTP_RESPONSE_TIMEOUT to a value smaller than CURLOPT_TIMEOUT. (Added in 7.10.8)
CURLOPT_FTP_ALTERNATIVE_TO_USER
Pass a char * as parameter, pointing to a string which will be used to authenticate if the
usual FTP "USER user" and "PASS password" negotiation fails. This is currently only known to
be required when connecting to Tumbleweed's Secure Transport FTPS server using client certifi-cates certificates
cates for authentication. (Added in 7.15.5)
CURLOPT_FTP_SKIP_PASV_IP
Pass a long. If set to 1, it instructs libcurl to not use the IP address the server suggests
in its 227-response to libcurl's PASV command when libcurl connects the data connection.
Instead libcurl will re-use the same IP address it already uses for the control connection.
But it will use the port number from the 227-response. (Added in 7.14.2)
This option has no effect if PORT, EPRT or EPSV is used instead of PASV.
CURLOPT_FTPSSLAUTH
Pass a long using one of the values from below, to alter how libcurl issues "AUTH TLS" or
"AUTH SSL" when FTP over SSL is activated (see CURLOPT_USE_SSL). (Added in 7.12.2)
CURLFTPAUTH_DEFAULT
Allow libcurl to decide.
CURLFTPAUTH_SSL
Try "AUTH SSL" first, and only if that fails try "AUTH TLS".
CURLFTPAUTH_TLS
Try "AUTH TLS" first, and only if that fails try "AUTH SSL".
CURLOPT_FTP_SSL_CCC
If enabled, this option makes libcurl use CCC (Clear Command Channel). It shuts down the
SSL/TLS layer after authenticating. The rest of the control channel communication will be
unencrypted. This allows NAT routers to follow the FTP transaction. Pass a long using one of
the values below. (Added in 7.16.1)
CURLFTPSSL_CCC_NONE
Don't attempt to use CCC.
CURLFTPSSL_CCC_PASSIVE
Do not initiate the shutdown, but wait for the server to do it. Do not send a reply.
CURLFTPSSL_CCC_ACTIVE
Initiate the shutdown and wait for a reply.
CURLOPT_FTP_ACCOUNT
Pass a pointer to a zero terminated string (or NULL to disable). When an FTP server asks for
"account data" after user name and password has been provided, this data is sent off using the
ACCT command. (Added in 7.13.0)
CURLOPT_FTP_FILEMETHOD
Pass a long that should have one of the following values. This option controls what method
libcurl should use to reach a file on a FTP(S) server. The argument should be one of the fol-lowing following
lowing alternatives:
CURLFTPMETHOD_MULTICWD
libcurl does a single CWD operation for each path part in the given URL. For deep hier-archies hierarchies
archies this means many commands. This is how RFC1738 says it should be done. This is
the default but the slowest behavior.
CURLFTPMETHOD_NOCWD
libcurl does no CWD at all. libcurl will do SIZE, RETR, STOR etc and give a full path
to the server for all these commands. This is the fastest behavior.
CURLFTPMETHOD_SINGLECWD
libcurl does one CWD with the full target directory and then operates on the file "nor-mally" "normally"
mally" (like in the multicwd case). This is somewhat more standards compliant than
'nocwd' but without the full penalty of 'multicwd'.
(Added in 7.15.1)
RTSP OPTIONS
CURLOPT_RTSP_REQUEST
Tell libcurl what kind of RTSP request to make. Pass one of the following RTSP enum values.
Unless noted otherwise, commands require the Session ID to be initialized. (Added in 7.20.0)
CURL_RTSPREQ_OPTIONS
Used to retrieve the available methods of the server. The application is responsible
for parsing and obeying the response. (The session ID is not needed for this method.)
(Added in 7.20.0)
CURL_RTSPREQ_DESCRIBE
Used to get the low level description of a stream. The application should note what
formats it understands in the 'Accept:' header. Unless set manually, libcurl will auto-matically automatically
matically fill in 'Accept: application/sdp'. Time-condition headers will be added to
Describe requests if the CURLOPT_TIMECONDITION option is active. (The session ID is not
needed for this method) (Added in 7.20.0)
CURL_RTSPREQ_ANNOUNCE
When sent by a client, this method changes the description of the session. For example,
if a client is using the server to record a meeting, the client can use Announce to
inform the server of all the meta-information about the session. ANNOUNCE acts like a
HTTP PUT or POST just like CURL_RTSPREQ_SET_PARAMETER (Added in 7.20.0)
CURL_RTSPREQ_SETUP
Setup is used to initialize the transport layer for the session. The application must
set the desired Transport options for a session by using the CURLOPT_RTSP_TRANSPORT
option prior to calling setup. If no session ID is currently set with CURLOPT_RTSP_SES-SION_ID, CURLOPT_RTSP_SESSION_ID,
SION_ID, libcurl will extract and use the session ID in the response to this request.
(The session ID is not needed for this method). (Added in 7.20.0)
CURL_RTSPREQ_PLAY
Send a Play command to the server. Use the CURLOPT_RANGE option to modify the playback
time (e.g. 'npt=10-15'). (Added in 7.20.0)
CURL_RTSPREQ_PAUSE
Send a Pause command to the server. Use the CURLOPT_RANGE option with a single value to
indicate when the stream should be halted. (e.g. npt='25') (Added in 7.20.0)
CURL_RTSPREQ_TEARDOWN
This command terminates an RTSP session. Simply closing a connection does not terminate
the RTSP session since it is valid to control an RTSP session over different connec-tions. connections.
tions. (Added in 7.20.0)
CURL_RTSPREQ_GET_PARAMETER
Retrieve a parameter from the server. By default, libcurl will automatically include a
Content-Type: text/parameters header on all non-empty requests unless a custom one is
set. GET_PARAMETER acts just like a HTTP PUT or POST (see CURL_RTSPREQ_SET_PARAMETER).
Applications wishing to send a heartbeat message (e.g. in the presence of a server-specified serverspecified
specified timeout) should send use an empty GET_PARAMETER request. (Added in 7.20.0)
CURL_RTSPREQ_SET_PARAMETER
Set a parameter on the server. By default, libcurl will automatically include a Con-tent-Type: Content-Type:
tent-Type: text/parameters header unless a custom one is set. The interaction with
SET_PARAMTER is much like a HTTP PUT or POST. An application may either use CUR-LOPT_UPLOAD CURLOPT_UPLOAD
LOPT_UPLOAD with CURLOPT_READDATA like a HTTP PUT, or it may use CURLOPT_POSTFIELDS
like a HTTP POST. No chunked transfers are allowed, so the application must set the
CURLOPT_INFILESIZE in the former and CURLOPT_POSTFIELDSIZE in the latter. Also, there
is no use of multi-part POSTs within RTSP. (Added in 7.20.0)
CURL_RTSPREQ_RECORD
Used to tell the server to record a session. Use the CURLOPT_RANGE option to modify the
record time. (Added in 7.20.0)
CURL_RTSPREQ_RECEIVE
This is a special request because it does not send any data to the server. The applica-tion application
tion may call this function in order to receive interleaved RTP data. It will return
after processing one read buffer of data in order to give the application a chance to
run. (Added in 7.20.0)
CURLOPT_RTSP_SESSION_ID
Pass a char * as a parameter to set the value of the current RTSP Session ID for the handle.
Useful for resuming an in-progress session. Once this value is set to any non-NULL value,
libcurl will return CURLE_RTSP_SESSION_ERROR if ID received from the server does not match. If
unset (or set to NULL), libcurl will automatically set the ID the first time the server sets
it in a response. (Added in 7.20.0)
CURLOPT_RTSP_STREAM_URI
Set the stream URI to operate on by passing a char * . For example, a single session may be
controlling rtsp://foo/twister/audio and rtsp://foo/twister/video and the application can
switch to the appropriate stream using this option. If unset, libcurl will default to operat-ing operating
ing on generic server options by passing '*' in the place of the RTSP Stream URI. This option
is distinct from CURLOPT_URL. When working with RTSP, the CURLOPT_STREAM_URI indicates what
URL to send to the server in the request header while the CURLOPT_URL indicates where to make
the connection to. (e.g. the CURLOPT_URL for the above examples might be set to
rtsp://foo/twister (Added in 7.20.0)
CURLOPT_RTSP_TRANSPORT
Pass a char * to tell libcurl what to pass for the Transport: header for this RTSP session.
This is mainly a convenience method to avoid needing to set a custom Transport: header for
every SETUP request. The application must set a Transport: header before issuing a SETUP
request. (Added in 7.20.0)
CURLOPT_RTSP_HEADER
This option is simply an alias for CURLOPT_HTTP_HEADER. Use this to replace the standard head-ers headers
ers that RTSP and HTTP share. It is also valid to use the shortcuts such as CURLOPT_USERAGENT.
(Added in 7.20.0)
CURLOPT_RTSP_CLIENT_CSEQ
Manually set the the CSEQ number to issue for the next RTSP request. Useful if the application
is resuming a previously broken connection. The CSEQ will increment from this new number
henceforth. (Added in 7.20.0)
CURLOPT_RTSP_SERVER_CSEQ
Manually set the CSEQ number to expect for the next RTSP Server->Client request. At the
moment, this feature (listening for Server requests) is unimplemented. (Added in 7.20.0)
PROTOCOL OPTIONS
CURLOPT_TRANSFERTEXT
A parameter set to 1 tells the library to use ASCII mode for FTP transfers, instead of the
default binary transfer. 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 cer-tain certain
tain characters, such as newlines or similar.
libcurl does not do a complete ASCII conversion when doing ASCII transfers over FTP. This is a
known limitation/flaw that nobody has rectified. libcurl simply sets the mode to ASCII and
performs a standard transfer.
CURLOPT_PROXY_TRANSFER_MODE
Pass a long. If the value is set to 1 (one), it tells libcurl to set the transfer mode (binary
or ASCII) for FTP transfers done via a HTTP proxy, by appending ;type=a or ;type=i to the URL.
Without this setting, or it being set to 0 (zero, the default), CURLOPT_TRANSFERTEXT has no
effect when doing FTP via a proxy. Beware that not all proxies support this feature. (Added
in 7.18.0)
CURLOPT_CRLF
Pass a long. If the value is set to 1 (one), libcurl converts Unix newlines to CRLF newlines
on transfers. Disable this option again by setting the value to 0 (zero).
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 tech-niques). techniques).
niques). For RTSP, the formatting of a range should follow RFC2326 Section 12.29. For RTSP,
byte ranges are not permitted. Instead, ranges should be given in npt, utc, or smpte formats.
Pass a NULL to this option to disable the use of ranges.
Ranges work on HTTP, FTP, FILE (since 7.18.0), and RTSP (since 7.20.0) transfers only.
CURLOPT_RESUME_FROM
Pass a long as parameter. It contains the offset in number of bytes that you want the transfer
to start from. Set this option to 0 to make the transfer start from the beginning (effectively
disabling resume). For FTP, set this option to -1 to make the transfer start from the end of
the target file (useful to continue an interrupted upload).
When doing uploads with FTP, the resume position is where in the local/source file libcurl
should try to resume the upload from and it will then append the source file to the remote
target file.
CURLOPT_RESUME_FROM_LARGE
Pass a curl_off_t as parameter. It contains the offset in number of bytes that you want the
transfer to start from. (Added in 7.11.0)
CURLOPT_CUSTOMREQUEST
Pass a pointer to a zero terminated string as parameter. It can be used to specify the request
instead of GET or HEAD when performing HTTP based requests, instead of LIST and NLST when per-forming performing
forming FTP directory listings and instead of LIST and RETR when issuing POP3 based commands.
This is particularly useful, for example, for performing a HTTP DELETE request or a POP3 DELE
command.
Please don't perform this at will, on HTTP based requests, by making sure your server supports
the command you are sending first.
When you change the request method by setting CURLOPT_CUSTOMREQUEST to something, you don't
actually change how libcurl behaves or acts in regards to the particular request method, it
will only change the actual string sent in the request.
For example:
With the HTTP protocol when you tell libcurl to do a HEAD request, but then specify a GET
though a custom request libcurl will still act as if it sent a HEAD. To switch to a proper
HEAD use CURLOPT_NOBODY, to switch to a proper POST use CURLOPT_POST or CURLOPT_POSTFIELDS and
to switch to a proper GET use CURLOPT_HTTPGET.
With the POP3 protocol when you tell libcurl to use a custom request it will behave like a
LIST or RETR command was sent where it expects data to be returned by the server. As such CUR-LOPT_NOBODY CURLOPT_NOBODY
LOPT_NOBODY should be used when specifying commands such as DELE and NOOP for example.
Restore to the internal default by setting this to NULL.
Many people have wrongly used this option to replace the entire request with their own,
including multiple headers and POST contents. While that might work in many cases, it will
cause libcurl to send invalid requests and it could possibly confuse the remote server badly.
Use CURLOPT_POST and CURLOPT_POSTFIELDS to set POST data. Use CURLOPT_HTTPHEADER to replace or
extend the set of headers sent by libcurl. Use CURLOPT_HTTP_VERSION to change HTTP version.
(Support for POP3 added in 7.26.0)
CURLOPT_FILETIME
Pass a long. If it is 1, libcurl will attempt to get the modification date of the remote docu-ment document
ment 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).
CURLOPT_NOBODY
A parameter set to 1 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. On HTTP(S) servers, this
will make libcurl do a HEAD request.
To change request to GET, you should use CURLOPT_HTTPGET. Change request to POST with CUR-LOPT_POST CURLOPT_POST
LOPT_POST etc.
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. This value should be passed as a long. See also CUR-LOPT_INFILESIZE_LARGE. CURLOPT_INFILESIZE_LARGE.
LOPT_INFILESIZE_LARGE.
For uploading using SCP, this option or CURLOPT_INFILESIZE_LARGE is mandatory.
When sending emails using SMTP, this command can be used to specify the optional SIZE parame-ter parameter
ter for the MAIL FROM command. (Added in 7.23.0)
This option does not limit how much data libcurl will actually send, as that is controlled
entirely by what the read callback returns.
CURLOPT_INFILESIZE_LARGE
When uploading a file to a remote site, this option should be used to tell libcurl what the
expected size of the infile is. This value should be passed as a curl_off_t. (Added in
7.11.0)
For uploading using SCP, this option or CURLOPT_INFILESIZE is mandatory.
This option does not limit how much data libcurl will actually send, as that is controlled
entirely by what the read callback returns.
CURLOPT_UPLOAD
A parameter set to 1 tells the library to prepare for an upload. The CURLOPT_READDATA and CUR-LOPT_INFILESIZE CURLOPT_INFILESIZE
LOPT_INFILESIZE or CURLOPT_INFILESIZE_LARGE options are also interesting for uploads. If the
protocol is HTTP, uploading means using the PUT request unless you tell libcurl otherwise.
Using PUT with HTTP 1.1 implies the use of a "Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
If you use PUT to a HTTP 1.1 server, you can upload data without knowing the size before
starting the transfer if you use chunked encoding. You enable this by adding a header like
"Transfer-Encoding: chunked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or without chunked trans-fer, transfer,
fer, you must specify the size.
CURLOPT_MAXFILESIZE
Pass a long as parameter. This allows you to specify the maximum size (in bytes) of a file to
download. If the file requested is larger than this value, the transfer will not start and
CURLE_FILESIZE_EXCEEDED will be returned.
The file size is not always known prior to download, and for such files this option has no
effect even if the file transfer ends up being larger than this given limit. This concerns
both FTP and HTTP transfers.
CURLOPT_MAXFILESIZE_LARGE
Pass a curl_off_t as parameter. This allows you to specify the maximum size (in bytes) of a
file to download. If the file requested is larger than this value, the transfer will not start
and CURLE_FILESIZE_EXCEEDED will be returned. (Added in 7.11.0)
The file size is not always known prior to download, and for such files this option has no
effect even if the file transfer ends up being larger than this given limit. This concerns
both FTP and HTTP transfers.
CURLOPT_TIMECONDITION
Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE time value is treated. You
can set this parameter to CURL_TIMECOND_IFMODSINCE or CURL_TIMECOND_IFUNMODSINCE. This feature
applies to HTTP, FTP, RTSP, and FILE.
The last modification time of a file is not always known and in such instances this feature
will have no effect even if the given time condition would not have been met. curl_easy_get-info(3) curl_easy_getinfo(3)
info(3) with the CURLINFO_CONDITION_UNMET option can be used after a transfer to learn if a
zero-byte successful "transfer" was due to this condition not matching.
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.
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.
In unix-like systems, this might cause signals to be used unless CURLOPT_NOSIGNAL is set.
Default timeout is 0 (zero) which means it never times out.
CURLOPT_TIMEOUT_MS
Like CURLOPT_TIMEOUT but takes number of milliseconds instead. If libcurl is built to use the
standard system name resolver, that portion of the transfer will still use full-second resolu-tion resolution
tion for timeouts with a minimum timeout allowed of one second. (Added in 7.16.2)
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_MAX_SEND_SPEED_LARGE
Pass a curl_off_t as parameter. If an upload exceeds this speed (counted in bytes per second)
on cumulative average during the transfer, the transfer will pause to keep the average rate
less than or equal to the parameter value. Defaults to unlimited speed. (Added in 7.15.5)
CURLOPT_MAX_RECV_SPEED_LARGE
Pass a curl_off_t as parameter. If a download exceeds this speed (counted in bytes per sec-ond) second)
ond) on cumulative average during the transfer, the transfer will pause to keep the average
rate less than or equal to the parameter value. Defaults to unlimited speed. (Added in 7.15.5)
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 in this easy
handle. Default is 5, and there isn't much point in changing this value unless you are per-fectly perfectly
fectly aware of how this works and changes libcurl's behaviour. This concerns connections
using any of the protocols that support persistent connections.
When reaching the maximum limit, curl closes the oldest one in the cache to prevent increasing
the number of open connections.
If you already have performed transfers with this curl handle, setting a smaller MAXCONNECTS
than before may cause open connections to get closed unnecessarily.
If you add this easy handle to a multi handle, this setting is not acknowledged, and you must
instead use curl_multi_setopt(3) and the CURLMOPT_MAXCONNECTS option.
CURLOPT_CLOSEPOLICY
(Obsolete) This option does nothing.
CURLOPT_FRESH_CONNECT
Pass a long. Set to 1 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).
CURLOPT_FORBID_REUSE
Pass a long. Set to 1 to make the next transfer explicitly close the connection when done.
Normally, libcurl keeps all connections alive when done with one transfer in case a succeeding
one follows 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 possible later
re-use (default behavior).
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 switch to the default built-in connection timeout - 300 sec-onds. seconds.
onds. See also the CURLOPT_TIMEOUT option.
In unix-like systems, this might cause signals to be used unless CURLOPT_NOSIGNAL is set.
CURLOPT_CONNECTTIMEOUT_MS
Like CURLOPT_CONNECTTIMEOUT but takes the number of milliseconds instead. If libcurl is built
to use the standard system name resolver, that portion of the connect will still use full-sec-ond full-second
ond resolution for timeouts with a minimum timeout allowed of one second. (Added in 7.16.2)
CURLOPT_IPRESOLVE
Allows an application to select what kind of IP addresses to use when resolving host names.
This is only interesting when using host names that resolve addresses using more than one ver-sion version
sion of IP. The allowed values are:
CURL_IPRESOLVE_WHATEVER
Default, resolves addresses to all IP versions that your system allows.
CURL_IPRESOLVE_V4
Resolve to IPv4 addresses.
CURL_IPRESOLVE_V6
Resolve to IPv6 addresses.
CURLOPT_CONNECT_ONLY
Pass a long. If the parameter equals 1, it tells the library to perform all the required proxy
authentication and connection setup, but no data transfer. This option is implemented for
HTTP, SMTP and POP3.
The option can be used to simply test a connection to a server, but is more useful when used
with the CURLINFO_LASTSOCKET option to curl_easy_getinfo(3) as the library can set up the con-nection connection
nection and then the application can obtain the most recently used socket for special data
transfers. (Added in 7.15.2)
CURLOPT_USE_SSL
Pass a long using one of the values from below, to make libcurl use your desired level of SSL
for the transfer. (Added in 7.11.0)
This is for enabling SSL/TLS when you use FTP, SMTP, POP3, IMAP etc.
(This option was known as CURLOPT_FTP_SSL up to 7.16.4, and the constants were known as
CURLFTPSSL_*)
CURLUSESSL_NONE
Don't attempt to use SSL.
CURLUSESSL_TRY
Try using SSL, proceed as normal otherwise.
CURLUSESSL_CONTROL
Require SSL for the control connection or fail with CURLE_USE_SSL_FAILED.
CURLUSESSL_ALL
Require SSL for all communication or fail with CURLE_USE_SSL_FAILED.
CURLOPT_RESOLVE
Pass a pointer to a linked list of strings with host name resolve information to use for
requests with this handle. 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.
Each single name resolve string should be written using the format HOST:PORT:ADDRESS where
HOST is the name libcurl will try to resolve, PORT is the port number of the service where
libcurl wants to connect to the HOST and ADDRESS is the numerical IP address. If libcurl is
built to support IPv6, ADDRESS can of course be either IPv4 or IPv6 style addressing.
This option effectively pre-populates the DNS cache with entries for the host+port pair so
redirects and everything that operations against the HOST+PORT will instead use your provided
ADDRESS.
You can remove names from the DNS cache again, to stop providing these fake resolves, by
including a string in the linked list that uses the format "-HOST:PORT". The host name must be
prefixed with a dash, and the host name and port number must exactly match what was already
added previously.
(Added in 7.21.3)
CURLOPT_DNS_SERVERS
Set the list of DNS servers to be used instead of the system default. The format of the dns
servers option is:
host[:port][,host[:port]]...
For example:
192.168.1.100,192.168.1.101,3.4.5.6
This option requires that libcurl was built with a resolver backend that supports this opera-tion. operation.
tion. The c-ares backend is the only such one.
(Added in 7.24.0)
CURLOPT_ACCEPTTIMEOUT_MS
Pass a long telling libcurl the maximum number of milliseconds to wait for a server to connect
back to libcurl when an active FTP connection is used. If no timeout is set, the internal
default of 60000 will be used. (Added in 7.24.0)
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.
With NSS this can also be the nickname of the certificate you wish to authenticate with. If
you want to use a file from the current directory, please precede it with "./" prefix, in
order to avoid confusion with a nickname.
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_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.
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".
The format "ENG" enables you to load the private key from a crypto engine. In this case CUR-LOPT_SSLKEY CURLOPT_SSLKEY
LOPT_SSLKEY is used as an identifier passed to the engine. You have to set the crypto engine
with CURLOPT_SSLENGINE. "DER" format key file currently does not work because of a bug in
OpenSSL.
CURLOPT_KEYPASSWD
Pass a pointer to a zero terminated string as parameter. It will be used as the password
required to use the CURLOPT_SSLKEY or CURLOPT_SSH_PRIVATE_KEYFILE private key. You never
needed a pass phrase to load a certificate but you need one to load your private key.
(This option was known as CURLOPT_SSLKEYPASSWD up to 7.16.4 and CURLOPT_SSLCERTPASSWD up to
7.9.2)
CURLOPT_SSLENGINE
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.
If the crypto device cannot be loaded, CURLE_SSL_ENGINE_NOTFOUND is returned.
CURLOPT_SSLENGINE_DEFAULT
Sets the actual crypto engine as the default for (asymmetric) crypto operations.
If the crypto device cannot be set, CURLE_SSL_ENGINE_SETFAILED is returned.
Even though this option doesn't need any parameter, in some configurations curl_easy_setopt
might be defined as a macro taking exactly three arguments. Therefore, it's recommended to
pass 1 as parameter to this option.
CURLOPT_SSLVERSION
Pass a long as parameter to control what version of SSL/TLS to attempt to use. The available
options are:
CURL_SSLVERSION_DEFAULT
The default action. This will attempt to figure out the remote SSL protocol version,
i.e. either SSLv3 or TLSv1 (but not SSLv2, which became disabled by default with
7.18.1).
CURL_SSLVERSION_TLSv1
Force TLSv1
CURL_SSLVERSION_SSLv2
Force SSLv2
CURL_SSLVERSION_SSLv3
Force SSLv3
CURLOPT_SSL_VERIFYPEER
Pass a long as parameter. By default, curl assumes a value of 1.
This option determines whether curl verifies the authenticity of the peer's certificate. A
value of 1 means curl verifies; 0 (zero) means it doesn't.
When negotiating a SSL connection, the server sends a certificate indicating its identity.
Curl verifies whether the certificate is authentic, i.e. that you can trust that the server is
who the certificate says it is. This trust is based on a chain of digital signatures, rooted
in certification authority (CA) certificates you supply. curl uses a default bundle of CA
certificates (the path for that is determined at build time) and you can specify alternate
certificates with the CURLOPT_CAINFO option or the CURLOPT_CAPATH option.
When CURLOPT_SSL_VERIFYPEER is nonzero, and the verification fails to prove that the certifi-cate certificate
cate is authentic, the connection fails. When the option is zero, the peer certificate veri-fication verification
fication succeeds regardless.
Authenticating the certificate is not by itself very useful. You typically want to ensure
that the server, as authentically identified by its certificate, is the server you mean to be
talking to. Use CURLOPT_SSL_VERIFYHOST to control that. The check that the host name in the
certificate is valid for the host name you're connecting to is done independently of the CUR-LOPT_SSL_VERIFYPEER CURLOPT_SSL_VERIFYPEER
LOPT_SSL_VERIFYPEER option.
CURLOPT_CAINFO
Pass a char * to a zero terminated string naming a file holding one or more certificates to
verify the peer with. This makes sense only when used in combination with the CUR-LOPT_SSL_VERIFYPEER CURLOPT_SSL_VERIFYPEER
LOPT_SSL_VERIFYPEER option. If CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAINFO need not even
indicate an accessible file.
This option is by default set to the system path where libcurl's cacert bundle is assumed to
be stored, as established at build time.
If curl is built against the NSS SSL library, the NSS PEM PKCS#11 module (libnsspem.so) needs
to be available for this option to work properly.
CURLOPT_ISSUERCERT
Pass a char * to a zero terminated string naming a file holding a CA certificate in PEM for-mat. format.
mat. If the option is set, an additional check against the peer certificate is performed to
verify the issuer is indeed the one associated with the certificate provided by the option.
This additional check is useful in multi-level PKI where one needs to enforce that the peer
certificate is from a specific branch of the tree.
This option makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER option.
Otherwise, the result of the check is not considered as failure.
A specific error code (CURLE_SSL_ISSUER_ERROR) is defined with the option, which is returned
if the setup of the SSL/TLS session has failed due to a mismatch with the issuer of peer cer-tificate certificate
tificate (CURLOPT_SSL_VERIFYPEER has to be set too for the check to fail). (Added in 7.19.0)
CURLOPT_CAPATH
Pass a char * to a zero terminated string naming a directory holding multiple CA certificates
to verify the peer with. If libcurl is built against OpenSSL, the certificate directory must
be prepared using the openssl c_rehash utility. This makes sense only when used in combina-tion combination
tion with the CURLOPT_SSL_VERIFYPEER option. If CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAP-ATH CURLOPT_CAPATH
ATH need not even indicate an accessible path. The CURLOPT_CAPATH function apparently does
not work in Windows due to some limitation in openssl. This option is OpenSSL-specific and
does nothing if libcurl is built to use GnuTLS. NSS-powered libcurl provides the option only
for backward compatibility.
CURLOPT_CRLFILE
Pass a char * to a zero terminated string naming a file with the concatenation of CRL (in PEM
format) to use in the certificate validation that occurs during the SSL exchange.
When curl is built to use NSS or GnuTLS, there is no way to influence the use of CRL passed to
help in the verification process. When libcurl is built with OpenSSL support,
X509_V_FLAG_CRL_CHECK and X509_V_FLAG_CRL_CHECK_ALL are both set, requiring CRL check against
all the elements of the certificate chain if a CRL file is passed.
This option makes sense only when used in combination with the CURLOPT_SSL_VERIFYPEER option.
A specific error code (CURLE_SSL_CRL_BADFILE) is defined with the option. It is returned when
the SSL exchange fails because the CRL file cannot be loaded. A failure in certificate veri-fication verification
fication due to a revocation information found in the CRL does not trigger this specific
error. (Added in 7.19.0)
CURLOPT_SSL_VERIFYHOST
Pass a long as parameter.
This option determines whether libcurl verifies that the server cert is for the server it is
known as.
When negotiating a SSL connection, the server sends a certificate indicating its identity.
When CURLOPT_SSL_VERIFYHOST is 2, that certificate must indicate that the server is the server
to which you meant to connect, or the connection fails.
Curl considers the server the intended one when the Common Name field or a Subject Alternate
Name field in the certificate matches the host name in the URL to which you told Curl to con-nect. connect.
nect.
When the value is 1, libcurl will return a failure. It was previously (in 7.28.0 and earlier)
a debug option of some sorts, but it is no longer supported due to frequently leading to pro-grammer programmer
grammer mistakes.
When the value is 0, the connection succeeds regardless of the names in the certificate.
The default value for this option is 2.
This option controls checking the server's certificate's claimed identity. The server could
be lying. To control lying, see CURLOPT_SSL_VERIFYPEER. If libcurl is built against NSS and
CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_SSL_VERIFYHOST is ignored.
CURLOPT_CERTINFO
Pass a long set to 1 to enable libcurl's certificate chain info gatherer. With this enabled,
libcurl (if built with OpenSSL) will extract lots of information and data about the certifi-cates certificates
cates in the certificate chain used in the SSL connection. This data is then possible to
extract after a transfer using curl_easy_getinfo(3) and its option CURLINFO_CERTINFO. (Added
in 7.19.1)
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 connec-tion connection
tion 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_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 syntactically 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.
For OpenSSL and GnuTLS 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
For NSS, valid examples of cipher lists include 'rsa_rc4_128_md5', 'rsa_aes_128_sha', etc.
With NSS you don't add/remove ciphers. If one uses this option then all known ciphers are dis-abled disabled
abled and only those passed in are enabled.
You'll find more details about the NSS cipher lists on this URL: http://git .fedora-
hosted.org/cgit/mod_nss.git/plain/docs/mod_nss.html#Directives
CURLOPT_SSL_SESSIONID_CACHE
Pass a long set to 0 to disable libcurl's use of SSL session-ID caching. Set this to 1 to
enable it. By default all transfers are done using the cache. While nothing ever should get
hurt by attempting to reuse SSL session-IDs, there seem to be broken SSL implementations in
the wild that may require you to disable this in order for you to succeed. (Added in 7.16.0)
CURLOPT_SSL_OPTIONS
Pass a long with a bitmask to tell libcurl about specific SSL behaviors.
CURLSSLOPT_ALLOW_BEAST is the only supported bit and by setting this the user will tell
libcurl to not attempt to use any workarounds for a security flaw in the SSL3 and TLS1.0 pro-tocols. protocols.
tocols. If this option isn't used or this bit is set to 0, the SSL layer libcurl uses may use
a work-around for this flaw although it might cause interoperability problems with some
(older) SSL implementations. WARNING: avoiding this work-around loosens the security, and by
setting this option to 1 you ask for exactly that. (Added in 7.25.0)
CURLOPT_KRBLEVEL
Pass a char * as parameter. Set the kerberos security level for FTP; this also enables ker-beros kerberos
beros 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 kerberos support for FTP.
(This option was known as CURLOPT_KRB4LEVEL up to 7.16.3)
CURLOPT_GSSAPI_DELEGATION
Set the parameter to CURLGSSAPI_DELEGATION_FLAG to allow unconditional GSSAPI credential dele-gation. delegation.
gation. The delegation is disabled by default since 7.21.7. Set the parameter to CURLGSS-API_DELEGATION_POLICY_FLAG CURLGSSAPI_DELEGATION_POLICY_FLAG
API_DELEGATION_POLICY_FLAG to delegate only if the OK-AS-DELEGATE flag is set in the service
ticket in case this feature is supported by the GSSAPI implementation and the definition of
GSS_C_DELEG_POLICY_FLAG was available at compile-time. (Added in 7.22.0)
SSH OPTIONS
CURLOPT_SSH_AUTH_TYPES
Pass a long set to a bitmask consisting of one or more of CURLSSH_AUTH_PUBLICKEY,
CURLSSH_AUTH_PASSWORD, CURLSSH_AUTH_HOST, CURLSSH_AUTH_KEYBOARD and CURLSSH_AUTH_AGENT. Set
CURLSSH_AUTH_ANY to let libcurl pick a suitable one. Currently CURLSSH_AUTH_HOST has no
effect. (Added in 7.16.1) If CURLSSH_AUTH_AGENT is used, libcurl attempts to connect to ssh-agent sshagent
agent or pageant and let the agent attempt the authentication. (Added in 7.28.0)
CURLOPT_SSH_HOST_PUBLIC_KEY_MD5
Pass a char * pointing to a string containing 32 hexadecimal digits. The string should be the
128 bit MD5 checksum of the remote host's public key, and libcurl will reject the connection
to the host unless the md5sums match. This option is only for SCP and SFTP transfers. (Added
in 7.17.1)
CURLOPT_SSH_PUBLIC_KEYFILE
Pass a char * pointing to a file name for your public key. If not used, libcurl defaults to
$HOME/.ssh/id_dsa.pub if the HOME environment variable is set, and just "id_dsa.pub" in the
current directory if HOME is not set. (Added in 7.16.1) If an empty string is passed, libcurl
will pass no public key to libssh2 which then tries to compute it from the private key, this
is known to work when libssh2 1.4.0+ is linked against OpenSSL. (Added in 7.26.0)
CURLOPT_SSH_PRIVATE_KEYFILE
Pass a char * pointing to a file name for your private key. If not used, libcurl defaults to
$HOME/.ssh/id_dsa if the HOME environment variable is set, and just "id_dsa" in the current
directory if HOME is not set. If the file is password-protected, set the password with CUR-LOPT_KEYPASSWD. CURLOPT_KEYPASSWD.
LOPT_KEYPASSWD. (Added in 7.16.1)
CURLOPT_SSH_KNOWNHOSTS
Pass a pointer to a zero terminated string holding the file name of the known_host file to
use. The known_hosts file should use the OpenSSH file format as supported by libssh2. If this
file is specified, libcurl will only accept connections with hosts that are known and present
in that file, with a matching public key. Use CURLOPT_SSH_KEYFUNCTION to alter the default
behavior on host and key (mis)matching. (Added in 7.19.6)
CURLOPT_SSH_KEYFUNCTION
Pass a pointer to a curl_sshkeycallback function. It gets called when the known_host matching
has been done, to allow the application to act and decide for libcurl how to proceed. The
callback will only be called if CURLOPT_SSH_KNOWNHOSTS is also set.
The curl_sshkeycallback function gets passed the CURL handle, the key from the known_hosts
file, the key from the remote site, info from libcurl on the matching status and a custom
pointer (set with CURLOPT_SSH_KEYDATA). It MUST return one of the following return codes to
tell libcurl how to act:
CURLKHSTAT_FINE_ADD_TO_FILE
The host+key is accepted and libcurl will append it to the known_hosts file before con-tinuing continuing
tinuing with the connection. This will also add the host+key combo to the known_host
pool kept in memory if it wasn't already present there. The adding of data to the file
is done by completely replacing the file with a new copy, so the permissions of the
file must allow this.
CURLKHSTAT_FINE
The host+key is accepted libcurl will continue with the connection. This will also add
the host+key combo to the known_host pool kept in memory if it wasn't already present
there.
CURLKHSTAT_REJECT
The host+key is rejected. libcurl will deny the connection to continue and it will be
closed.
CURLKHSTAT_DEFER
The host+key is rejected, but the SSH connection is asked to be kept alive. This fea-ture feature
ture could be used when the app wants to somehow return back and act on the host+key
situation and then retry without needing the overhead of setting it up from scratch
again.
(Added in 7.19.6)
CURLOPT_SSH_KEYDATA
Pass a void * as parameter. This pointer will be passed along verbatim to the callback set
with CURLOPT_SSH_KEYFUNCTION. (Added in 7.19.6)
OTHER OPTIONS
CURLOPT_PRIVATE
Pass a void * as parameter, pointing to data that should be associated with this curl handle.
The pointer can subsequently be retrieved using curl_easy_getinfo(3) with the CURLINFO_PRIVATE
option. libcurl itself does nothing with this data. (Added in 7.10.3)
CURLOPT_SHARE
Pass a share handle as a parameter. The share handle must have been created by a previous call
to curl_share_init(3). Setting this option, will make this curl handle use the data from the
shared handle instead of keeping the data to itself. This enables several curl handles to
share data. If the curl handles are used simultaneously in multiple threads, you MUST use the
locking methods in the share handle. See curl_share_setopt(3) for details.
If you add a share that is set to share cookies, your easy handle will use that cookie cache
and get the cookie engine enabled. If you unshare an object that was using cookies (or change
to another object that doesn't share cookies), the easy handle will get its cookie engine dis-abled. disabled.
abled.
Data that the share object is not set to share will be dealt with the usual way, as if no
share was used.
CURLOPT_NEW_FILE_PERMS
Pass a long as a parameter, containing the value of the permissions that will be assigned to
newly created files on the remote server. The default value is _644, but any valid value can
be used. The only protocols that can use this are sftp://, scp://, and file://. (Added in
7.16.4)
CURLOPT_NEW_DIRECTORY_PERMS
Pass a long as a parameter, containing the value of the permissions that will be assigned to
newly created directories on the remote server. The default value is _755, but any valid
value can be used. The only protocols that can use this are sftp://, scp://, and file://.
(Added in 7.16.4)
TELNET OPTIONS
CURLOPT_TELNETOPTIONS
Provide a pointer to a curl_slist with variables to pass to the telnet negotiations. The vari-ables variables
ables should be in the format <option=value>. libcurl supports the options 'TTYPE', 'XDISPLOC'
and 'NEW_ENV'. See the TELNET standard for details.
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.
If you try to set an option that libcurl doesn't know about, perhaps because the library is too old
to support it or the option was removed in a recent version, this function will return
CURLE_FAILED_INIT.
SEE ALSO
curl_easy_init(3), curl_easy_cleanup(3), curl_easy_reset(3)
libcurl 7.20.0 1 Jan 2010 curl_easy_setopt(3)
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