curl_easy_setopt(3) libcurl Manual curl_easy_setopt(3)NAMEcurl_easy_setopt - set options for a curl easy handle
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter);
DESCRIPTIONcurl_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 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 handle. The options are not in any way
reset between transfers, so if you want subsequent transfers with dif‐
ferent 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 CUR‐
LOPT_STDERR.
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 actu‐
ally have headers preceding the data (like HTTP).
CURLOPT_NOPROGRESS
Pass a long. If set to 1, it tells the library to shut off the
progress meter completely. It will also present the CURLOPT_PRO‐
GRESSFUNCTION from getting called.
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 risking getting signals. (Added in 7.10)
If this option is set and libcurl has been built with the stan‐
dard name resolver, timeouts will not occur while the name
resolve takes place. Consider building libcurl with c-ares sup‐
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 sys‐
tem 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 operating 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 sig‐
nal 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 imple‐
mentation. 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 con‐
structed:
ftp://example.com/some/path/[a-z[:upper:]\\].jpeg
(This was added in 7.21.0)
CALLBACK OPTIONS
CURLOPT_WRITEFUNCTION
Function pointer that should match 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 trans‐
ferred 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 *' as
libcurl will pass this to fwrite() when writing data.
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 CUR‐
LOPT_WRITEFUNCTION if you set this option or you will experience
crashes.
This option is also known with the older name CURLOPT_FILE, the
name CURLOPT_WRITEDATA was introduced in 7.9.7.
CURLOPT_READFUNCTION
Function pointer that should match the following prototype:
size_t function( void *ptr, size_t size, size_t nmemb, void
*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 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 *.
If you're using libcurl as a win32 DLL, you MUST use a CUR‐
LOPT_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
Function pointer that should match the curl_ioctl_callback pro‐
totype found in <curl/curl.h>. 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. (Option added in
7.12.3).
Use CURLOPT_SEEKFUNCTION instead to provide 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_IOCTL‐
FUNCTION. (Option added in 7.12.3)
CURLOPT_SEEKFUNCTION
Function pointer that should match 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 authenti‐
cation 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
callback 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 lat‐
ter can sometimes be done by instead reading from the input or
similar.
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
Function pointer that should match the curl_sockopt_callback
prototype found in <curl/curl.h>. 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, and currently only one value is sup‐
ported: CURLSOCKTYPE_IPCXN for the primary connection (meaning
the control connection in the FTP case). 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 unre‐
coverable 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_SOCK‐
OPT_ALREADY_CONNECTED, which tells libcurl that the socket is in
fact already connected and then libcurl will not attempt to con‐
nect it.
CURLOPT_SOCKOPTDATA
Pass a pointer that will be untouched by libcurl and passed as
the first argument in the sockopt callback set with CUR‐
LOPT_SOCKOPTFUNCTION. (Option added in 7.16.0)
CURLOPT_OPENSOCKETFUNCTION
Function pointer that should match the curl_opensocket_callback
prototype found in <curl/curl.h>. 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 callback
function should return the socket or CURL_SOCKET_BAD in case no
connection should be established or any error detected. Any
additional setsockopt(2) calls can be done on the socket at the
user's discretion. CURL_SOCKET_BAD return value from the call‐
back 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 CUR‐
LOPT_OPENSOCKETFUNCTION. (Option added in 7.17.1.)
CURLOPT_CLOSESOCKETFUNCTION
Function pointer that should match the curl_closesocket_callback
prototype found in <curl/curl.h>. This function gets called by
libcurl instead of the close(3) or closesocket(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 closesocket callback set with CUR‐
LOPT_CLOSESOCKETFUNCTION. (Option added in 7.21.7)
CURLOPT_PROGRESSFUNCTION
Function pointer that should match the curl_progress_callback
prototype found in <curl/curl.h>. This function gets called by
libcurl instead of its internal equivalent with a frequent
interval during operation (roughly once per second or sooner) no
matter if data is being transfered or not. Unknown/unused argu‐
ment values passed to the callback will be set to zero (like if
you only download data, the upload size will remain 0). Return‐
ing 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 actu‐
ally 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 CUR‐
LOPT_PROGRESSFUNCTION.
CURLOPT_HEADERFUNCTION
Function pointer that should match 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 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 CUR‐
LOPT_HEADERDATA (CURLOPT_WRITEHEADER) 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 CUR‐
LOPT_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 func‐
tion 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_HEADERFUNCTION 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
Function pointer that should match 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 information, 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 CUR‐
LOPT_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 function‐
ality is absent.
Function pointer that should match the following prototype:
CURLcode sslctxfun(CURL *curl, void *sslctx, void *parm); This
function gets called by libcurl just before the initialization
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 negotiation. 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 validation
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, certificate
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
Function pointers that should match 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_version_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_NET‐
WORK_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 call‐
back 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 differ‐
ent on your system.
CURLOPT_INTERLEAVEFUNCTION
Function pointer that should match 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 pro‐
tocol unit (e.g. one RTP packet). Curl writes the interleaved
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 RFC 2326 Section 10.12 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 challeneges for the client applica‐
tion. Since the stream data is sharing the RTSP control connec‐
tion, it is critical to service the RTP in a timely fashion. If
the RTP data is not handled quickly, subsequent response pro‐
cessing 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 CUR‐
LOPT_INTERLEAVEFUNCTION when interleaved RTP data is received.
(Added in 7.20.0)
CURLOPT_CHUNK_BGN_FUNCTION
Function pointer that should match 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_WILDCARD‐
MATCH 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
Function pointer that should match 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
Function pointer that should match 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 read‐
able 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 should keep the associated storage available until libcurl
no longer needs it. Failing to do so will cause very odd behav‐
ior 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 afterwards.
NETWORK OPTIONS
CURLOPT_URL
The actual URL to deal with. The parameter should be a char * to
a zero terminated string which must be URL-encoded in the fol‐
lowing format:
scheme://host:port/path
For a greater explanation of the format please see RFC 3986
(http://curl.haxx.se/rfc/rfc3986.txt).
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 sup‐
ported, 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 repre‐
sented 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 protocols, when connecting to servers
that require authentication.
For example the following types of authentication support this:
http://user:password@www.domain.com ftp://user:pass‐
word@ftp.domain.com pop3://user:password@mail.domain.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 exam‐
ples show how to specify the port:
http://www.weirdserver.com:8080/ - This will connect to a web
server using port 8080.
smtp://mail.domain.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 omitted
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.
http://www.netscape.com - This gets the main page (index.html in
this example) from Netscape's web server.
http://www.netscape.com/index.html - This returns the main page
from Netscape by specifying the page to get.
http://www.netscape.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 speci‐
fied. If the directory is omitted then the directory listing for
the root / home directory will be returned.
ftp://cool.haxx.se - This retrieves the directory listing for
our FTP server.
ftp://cool.haxx.se/readme.txt - This downloads the file
readme.txt from the root directory.
ftp://cool.haxx.se/libcurl/readme.txt - This downloads
readme.txt from the libcurl directory.
ftp://user:password@my.example.com/readme.txt - This retrieves
the readme.txt file from the user's home directory. When a user‐
name 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 specified by
prepending an additional forward slash to the beginning of the
path.
ftp://user:password@my.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 host name. However, this may not return the fully quali‐
fied domain name that is required by some mail servers and spec‐
ifying 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 getad‐
drinfo.
smtp://mail.domain.com - This connects to the mail server at
domain.com and sends your local computer's host name in the HELO
/ EHLO command.
smtp://mail.domain.com/client.domain.com - This will send
client.domain.com in the HELO / EHLO command to the mail server
at domain.com.
POP3
The path part of a POP3 request specifies the mailbox (message)
to retrieve. If the mailbox is not specified then a list of
waiting messages is returned instead.
pop3://user:password@mail.domain.com - This lists the available
messages pop3://user:password@mail.domain.com/1 - This retrieves
the first message
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 CURLOPT_USER‐
PWD 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 speci‐
fied. 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 CURLOPT_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 directory
sftp://ssh.example.com/~/Documents/ - This requests a directory
listing of the Documents directory under the user's home direc‐
tory
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 subset of them. By default libcurl will
accept all protocols it supports. See also CURLOPT_REDIR_PROTO‐
COLS. (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_FOLLOWLO‐
CATION 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 sepa‐
rate option. If not specified, libcurl will default to using
port 1080 for proxies. CURLOPT_PROXYPORT.
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_HTTPPROXYTUNNEL.
libcurl respects the environment variables http_proxy,
ftp_proxy, all_proxy etc, if any of those are set. The CUR‐
LOPT_PROXY option does however override any possibly set envi‐
ronment 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 vari‐
ables 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 proto‐
col:// prefix to specify alternative 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_HOSTNAME type) to request the specific
SOCKS version to be used. No protocol specified, http:// and 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 CURLPROXY_HTTP, CURLPROXY_HTTP_1_0 (added
in 7.19.4), CURLPROXY_SOCKS4 (added in 7.10), CURLPROXY_SOCKS5,
CURLPROXY_SOCKS4A (added in 7.18.0) and CURLPROXY_SOCKS5_HOST‐
NAME (added in 7.18.0). The HTTP type is default. (Added in
7.10)
If you set CURLOPT_PROXYTYPE to CURLPROXY_HTTP_1_0, it will only
affect how libcurl speaks to a proxy when CONNECT is used. The
HTTP version used for "regular" HTTP requests is instead con‐
trolled with CURLOPT_HTTP_VERSION.
CURLOPT_NOPROXY
Pass a pointer to a zero terminated string. This should be a
comma separated list of hosts which do not use a proxy, if one
is specified. The only wildcard 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, local.com would
match local.com, local.com:80, and www.local.com, but not
www.notlocal.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 ref‐
erence 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 interface name and no attempt will ever be
named to do treat it as an IP address or to do name resolution
on it. If the parameter starts with "host!" it is treated as
either an IP address or a hostname. Hostnames are resolved syn‐
chronously. 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 exist‐
ing 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 CUR‐
LOPT_INTERFACE and you are recommended to use CURLOPT_LOCALPOR‐
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 should 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 fail‐
ures. (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 information 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 CUR‐
LOPT_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 should 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 pur‐
pose 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 conges‐
tion 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 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, provided
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 sys‐
tem will wait while the connection 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 sending keepalive probes. Not all oper‐
ating 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 informa‐
tion in the URL is to be preferred. 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 infor‐
mation in the URL.
This is the default.
CURL_NETRC_REQUIRED
This value tells the library that use of the file is
required, to ignore the information in the URL, and to
search the file 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 CURLOPT_NETRC
is set, libcurl will attempt to find a .netrc file in the cur‐
rent user's home directory. (Added in 7.10.9)
CURLOPT_USERPWD
Pass a char * as parameter, which should be [user name]:[pass‐
word] 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 per‐
form 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 acciden‐
tal information leakage.
CURLOPT_PROXYUSERPWD
Pass a char * as parameter, which should be [user name]:[pass‐
word] to use for the connection to the HTTP proxy. Use CUR‐
LOPT_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 CURLOPT_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 CUR‐
LOPT_PROXYUSERPWD the CURLOPT_PROXYUSERNAME allows the username
to contain a colon, like in the following example:
"sip:user@example.com". The CURLOPT_PROXYUSERNAME 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_PROX‐
YUSERPWD option.
In order to specify the password to be used in conjunction with
the user name use the CURLOPT_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 network 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 sup‐
ported virtually everywhere. This sends the user name and
password 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 authen‐
tication over public networks than the regular old-fash‐
ioned 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 sim‐
ply 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.
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 per‐
formed 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
systems, 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. In particular, the application must not uncondi‐
tionally 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 sin‐
gle specific auth value to force libcurl to probe for un-
restricted auth and if not, only that single auth algo‐
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 authenti‐
cation for TLS is defined in RFC 5054 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 ter‐
minated username to use for the TLS authentication method speci‐
fied 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 ter‐
minated password to use for the TLS authentication method speci‐
fied 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. 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 spe‐
cial 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 resonse sent using a compressed Transfer-
Encoding that will be automatically uncompressed by libcurl on
receival.
Transfer-Encoding differs slightly from the Content-Encoding you
ask for with CURLOPT_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 automati‐
cally follow. The accepted protocols are set with CUR‐
LOPT_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 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 RFC 2616/10.3.2 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. Setting bit 2 (value CURL_REDIR_POST_303)
makes libcurl maintain the request method after a 302 redirect.
CURL_REDIR_POST_ALL is a convenience define that sets both 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 CUR‐
LOPT_FOLLOWLOCATION. (Added in 7.17.1) (This option was known
as CURLOPT_POST301 up to 7.19.0 as it only supported the 301 way
before then)
CURLOPT_PUT
A parameter set to 1 tells the library to use HTTP PUT to trans‐
fer data. The data should be set with CURLOPT_READDATA and CUR‐
LOPT_INFILESIZE.
This option is deprecated and starting with version 7.12.1 you
should instead use CURLOPT_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 CUR‐
LOPT_POSTFIELDSIZE_LARGE to set the data size.
Optionally, you can provide data to POST using the CURLOPT_READ‐
FUNCTION 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 chun‐
ked 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 set‐
ting your own with CURLOPT_HTTPHEADER.
Using POST with HTTP 1.1 implies the use of a "Expect: 100-con‐
tinue" header. You can disable this header with CURLOPT_HTTP‐
HEADER as usual.
If you use POST to a HTTP 1.1 server, you can send data without
knowing the size before starting the POST 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 transfer, you must specify the size in the
request.
When setting CURLOPT_POST to 1, it will automatically set CUR‐
LOPT_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 similar.
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 conse‐
quence, 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 Content-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 CUR‐
LOPT_POSTFIELDSIZE explicitly to zero, as simply setting CUR‐
LOPT_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-con‐
tinue" header. You can disable this header with CURLOPT_HTTP‐
HEADER 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 ver‐
sion 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_POST‐
FIELDS 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 CURLOPT_POSTFIELDSIZE or CUR‐
LOPT_POSTFIELDSIZE_LARGE: If the size has not been set prior to
CURLOPT_COPYPOSTFIELDS, the data are assumed to be a NUL-termi‐
nated 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 CUR‐
LOPT_POSTFIELDS or CURLOPT_COPYPOSTFIELDS 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-con‐
tinue" header. You can disable this header with CURLOPT_HTTP‐
HEADER as usual.
When setting CURLOPT_HTTPPOST, it will automatically set CUR‐
LOPT_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: 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_HTTP‐
HEADER.
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 inter‐
nally, 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. Failure 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, CURLOPT_USERAGENT and CURLOPT_REFERER.
CURLOPT_HTTP200ALIASES
Pass a pointer to a linked list of aliases to be treated as
valid HTTP 200 responses. Some servers respond with a custom
header response line. For example, IceCast servers respond with
"ICY 200 OK". By including this string in your list of aliases,
the response will be treated as a valid HTTP header line such as
"HTTP/1.0 200 OK". (Added in 7.10.3)
The linked list should be a fully valid list of struct
curl_slist structs, and be properly filled in. Use
curl_slist_append(3) to create the list and
curl_slist_free_all(3) to clean up an entire list.
The alias itself is not parsed for any version strings. Before
libcurl 7.16.3, Libcurl used the value set by option CUR‐
LOPT_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 han‐
dle, 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 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, indepen‐
dent 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 Net‐
scape / 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 speci‐
fied 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 (since 7.14.1).
CURLOPT_HTTP_VERSION
Pass a long, set to one of the values described below. They
force libcurl to use the specific HTTP versions. This is not
sensible to do unless you have a good reason.
CURL_HTTP_VERSION_NONE
We don't care about what version the library uses.
libcurl will use whatever it thinks fit.
CURL_HTTP_VERSION_1_0
Enforce HTTP 1.0 requests.
CURL_HTTP_VERSION_1_1
Enforce HTTP 1.1 requests.
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_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 send‐
ing 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 mes‐
sages 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 RFC-2554.
(Added in 7.24.0)
TFTP OPTIONS
CURLOPT_TFTP_BLKSIZE
Specify block size to use for TFTP data transmission. Valid
range as per RFC 2348 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 instruc‐
tion. 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, option‐
ally followed by a '-' to specify 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 avail‐
able, libcurl will report CURLE_FTP_PORT_FAILED for the handle.
Invalid port/range settings are ignored. IPv6 addresses fol‐
lowed 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 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 operation 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 commands).
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 CURLOPT_QUOTE. Disable this operation again by
setting a NULL to this option.
CURLOPT_PREQUOTE
Pass a pointer to a linked list of FTP commands to pass to the
server after the transfer type is set. The linked list should be
a fully valid list of struct curl_slist structs properly filled
in as described for CURLOPT_QUOTE. Disable this operation again
by setting a NULL to this option. 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 neces‐
sary.
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 directory 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 creation. (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 simultanoes 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 CURLOPT_TIMEOUT. It is recom‐
mended that if used in conjunction with CURLOPT_TIMEOUT, you set
CURLOPT_FTP_RESPONSE_TIMEOUT to a value smaller than CUR‐
LOPT_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 certificates 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 unen‐
crypted. 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 following
alternatives:
CURLFTPMETHOD_MULTICWD
libcurl does a single CWD operation for each path part in
the given URL. For deep hierarchies this means many com‐
mands. 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 "normally" (like in the multi‐
cwd 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 responsbile 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
automatically 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 descrip‐
tion 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 cur‐
rently set with CURLOPT_RTSP_SESSION_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 con‐
nections. (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/parame‐
ters 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 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 Content-Type: text/parameters
header unless a custom one is set. The interaction with
SET_PARAMTER is much like a HTTP PUT or POST. An applica‐
tion may either use CURLOPT_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 CUR‐
LOPT_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 application may call this func‐
tion 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 exam‐
ple, 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 operating 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 headers 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 bro‐
ken 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 certain characters, such as newlines or simi‐
lar.
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 per‐
forms 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 multi‐
ple intervals will cause the HTTP server to send the response
document in pieces (using standard MIME separation techniques).
For RTSP, the formatting of a range should follow RFC 2326 Sec‐
tion 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 con‐
tinue 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 per‐
forming HTTP based requests, instead of LIST and NLST when per‐
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_CUSTOMRE‐
QUEST 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: if you tell libcurl to do a HEAD request, but then
change the request to a "GET" with CURLOPT_CUSTOMREQUEST you'll
still see libcurl act as if it sent a HEAD even when it does
send a GET.
To switch to a proper HEAD, use CURLOPT_NOBODY, to switch to a
proper POST, use CURLOPT_POST or CURLOPT_POSTFIELDS and so on.
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 con‐
tents. 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 modifi‐
cation date of the remote document in this operation. This
requires that the remote server sends the time or replies to a
time querying command. The curl_easy_getinfo(3) function with
the CURLINFO_FILETIME argument can be used after a transfer to
extract the received time (if any).
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 CURLOPT_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 CURLOPT_INFILE‐
SIZE_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 parameter 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 CURLOPT_INFILESIZE or CURLOPT_INFILE‐
SIZE_LARGE options are also interesting for uploads. If the pro‐
tocol 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-con‐
tinue" header. You can disable this header with CURLOPT_HTTP‐
HEADER 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 transfer, 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_TIME‐
COND_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) 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 opera‐
tions 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 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 CUR‐
LOPT_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 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_MAXCONNECTS
Pass a long. The set number will be the persistent connection
cache size. The set amount will be the maximum amount of simul‐
taneously 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 perfectly 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 connec‐
tions 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 connec‐
tions 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 lim‐
its 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 seconds. 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-second
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 version 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 useful only on HTTP
URLs.
This option is useful with the CURLINFO_LASTSOCKET option to
curl_easy_getinfo(3). The library can set up the connection 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 for‐
mat 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 opera‐
tions 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 pre‐
fixed 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 operation. 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 for‐
mats 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 for‐
mats are "PEM", "DER" and "ENG".
The format "ENG" enables you to load the private key from a
crypto engine. In this case CURLOPT_SSLKEY is used as an identi‐
fier 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 con‐
figurations 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 certifi‐
cate indicating its identity. Curl verifies whether the cer‐
tificate 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 certificate is authentic, the connection
fails. When the option is zero, the peer certificate verifica‐
tion 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 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 CURLOPT_SSL_VERI‐
FYPEER option. If CURLOPT_SSL_VERIFYPEER is zero, CUR‐
LOPT_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.
When built against NSS, this is the directory that the NSS cer‐
tificate database resides in.
CURLOPT_ISSUERCERT
Pass a char * to a zero terminated string naming a file holding
a CA certificate in PEM format. If the option is set, an addi‐
tional 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 cer‐
tificate 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 ses‐
sion has failed due to a mismatch with the issuer of peer cer‐
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 combination with the CURLOPT_SSL_VERI‐
FYPEER option. If CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAP‐
ATH need not even indicate an accessible path. The CURLOPT_CAP‐
ATH 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 cer‐
tificate 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 verifi‐
cation 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 certifi‐
cate 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.
When the value is 1, the certificate must contain a Common Name
field, but it doesn't matter what name it says. (This is not
ordinarily a useful setting).
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 certificates
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 connection
will become.
CURLOPT_EGDSOCKET
Pass a char * to the zero terminated path name to the Entropy
Gathering Daemon socket. It will be used to seed the random
engine for SSL.
CURLOPT_SSL_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 sepa‐
rators 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 disabled and only those passed in are enabled.
You'll find more details about the NSS cipher lists on this URL:
http://directory.fedora.redhat.com/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 work-
arounds for a security flaw in the SSL3 and TLS1.0 protocols.
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 kerberos 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 uncon‐
ditional GSSAPI credential delegation. The delegation is dis‐
abled by default since 7.21.7. Set the parameter to CURLGSS‐
API_DELEGATION_POLICY_FLAG to delegate only if the OK-AS-DELE‐
GATE 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. Set CURLSSH_AUTH_ANY
to let libcurl pick one. Currently CURLSSH_AUTH_HOST has no
effect. (Added in 7.16.1)
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 cur‐
rent directory if HOME is not set. (Added in 7.16.1) If an
empty string is passed, libcurl will pass no public key to lib‐
ssh2 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-pro‐
tected, set the password with CURLOPT_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 appli‐
cation to act and decide for libcurl how to proceed. The call‐
back 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 fol‐
lowing 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 continuing with the connec‐
tion. 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 connec‐
tion 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 feature 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_PRI‐
VATE 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 han‐
dle 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 disabled.
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 permis‐
sions that will be assigned to newly created files on the remote
server. The default value is 0644, 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 permis‐
sions that will be assigned to newly created directories on the
remote server. The default value is 0755, 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 variables 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 ALSOcurl_easy_init(3), curl_easy_cleanup(3), curl_easy_reset(3)libcurl 7.20.0 1 Jan 2010 curl_easy_setopt(3)
