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curl_easy_setopt(3) libcurl Manual curl_easy_setopt(3)
NAME
curl_easy_setopt - set options for a curl easy handle
SYNOPSIS
#include
CURLcode curl_easy_setopt(CURL *handle, CURLoption option,
parameter);
DESCRIPTION
curl_easy_setopt() is used to tell libcurl how to behave.
By using the appropriate options to curl_easy_setopt, you
can change libcurl's behavior. All options are set with
the option followed by a parameter. That parameter can be
a long, a function pointer, an object pointer or a
curl_off_t, depending on what the specific option expects.
Read this manual carefully as bad input values may cause
libcurl to behave badly! You can only set one option in
each function call. A typical application 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 different options, you
must change them between the transfers. You can optionally
reset all options back to internal default with
curl_easy_reset(3).
Strings passed to libcurl as 'char *' arguments, will not
be copied by the library. Instead you should keep them
available until libcurl no longer needs them. Failing to
do so will cause very odd behavior or even crashes.
libcurl will need them until you call curl_easy_cleanup(3)
or you set the same option again to use a different
pointer.
The handle is the return code from a curl_easy_init(3) or
curl_easy_duphandle(3) call.
BEHAVIOR OPTIONS
CURLOPT_VERBOSE
Set the parameter to non-zero to get the library to
display a lot of verbose information about its
operations. Very useful for libcurl and/or protocol
debugging and understanding. The verbose informa-
tion will be sent to stderr, or the stream set with
CURLOPT_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 non-zero parameter tells the library to include
the header in the body output. This is only rele-
vant for protocols that actually have headers pre-
ceding the data (like HTTP).
CURLOPT_NOPROGRESS
A non-zero parameter tells the library to shut off
the built-in progress meter completely.
Future versions of libcurl is likely to not have
any built-in progress meter at all.
CURLOPT_NOSIGNAL
Pass a long. If it is non-zero, libcurl will not
use any functions that install signal handlers or
any functions that cause signals to be sent to the
process. This option is mainly here to allow multi-
threaded unix applications to still set/use all
timeout options etc, without risking getting sig-
nals. (Added in 7.10)
Consider building libcurl with ares support to
enable asynchronous DNS lookups. It enables nice
timeouts for name resolves without signals.
CALLBACK OPTIONS
CURLOPT_WRITEFUNCTION
Function pointer that should match the following
prototype: size_t function( void *ptr, size_t size,
size_t nmemb, void *stream); This function gets
called by libcurl as soon as there is data 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 dif-
fers from the amount passed to your function, it'll
signal an error to the library and it will abort
the transfer and return CURLE_WRITE_ERROR.
This function may be called with zero bytes data if
the transfered 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_WRITE-
DATA.
Set the stream 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 data that can be
passed to the write callback is defined in the
curl.h header file: CURL_MAX_WRITE_SIZE.
CURLOPT_WRITEDATA
Data pointer to pass to the file write function. 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 CURLOPT_WRITEFUNCTION if you set this
option or you will experience crashes.
This option is also known with the older name CUR-
LOPT_FILE, the name CURLOPT_WRITEDATA was intro-
duced in 7.9.7.
CURLOPT_READFUNCTION
Function pointer that should match the following
prototype: size_t function( void *ptr, size_t size,
size_t nmemb, void *stream); This function gets
called by libcurl as soon as it needs to read data
in order to send it to the peer. The data area
pointed at by the pointer ptr may be filled with at
most size multiplied with nmemb number of bytes.
Your function must return the actual number of
bytes that you stored in that memory area. Return-
ing 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 told 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)
If you set the callback pointer to NULL, or doesn't
set it at all, the default internal read function
will be used. It is simply doing an fread() on the
FILE * stream set with CURLOPT_READDATA.
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 spec-
ify 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 CURLOPT_READFUNCTION if you set this option.
This option is also known with the older name CUR-
LOPT_INFILE, the name CURLOPT_READDATA was intro-
duced in 7.9.7.
CURLOPT_IOCTLFUNCTION
Function pointer that should match the
curl_ioctl_callback prototype found in
. 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)
CURLOPT_IOCTLDATA
Pass a pointer that will be untouched by libcurl
and passed as the 3rd argument in the ioctl call-
back set with CURLOPT_IOCTLFUNCTION. (Option added
in 7.12.3)
CURLOPT_SOCKOPTFUNCTION
Function pointer that should match the curl_sock-
opt_callback prototype found in . 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 supported: CURLSOCKTYPE_IPCXN for the pri-
mary connection (meaning the control connection in
the FTP case). Future versions of libcurl may sup-
port more purposes. It passes the newly created
socket descriptor so additional setsockopt() calls
can be done at the user's discretion. A non-zero
return code from the callback function will signal
an unrecoverable error to the library and it will
close the socket and return CURLE_COULDNT_CONNECT.
(Option added in 7.15.6.)
CURLOPT_SOCKOPTDATA
Pass a pointer that will be untouched by libcurl
and passed as the first argument in the sockopt
callback set with CURLOPT_SOCKOPTFUNCTION. (Option
added in 7.15.6.)
CURLOPT_PROGRESSFUNCTION
Function pointer that should match the
curl_progress_callback prototype found in
. This function gets called by libcurl
instead of its internal equivalent with a frequent
interval during operation (roughly once per second)
no matter if data is being transfered or not.
Unknown/unused argument values passed to the call-
back will be set to zero (like if you only download
data, the upload size will remain 0). Returning a
non-zero value from this callback will cause
libcurl to abort the transfer and return
CURLE_ABORTED_BY_CALLBACK.
If you transfer data with the multi interface, this
function will not be called during periods of idle-
ness unless you call the appropriate libcurl func-
tion that performs transfers. Usage of the CUR-
LOPT_PROGRESSFUNCTION callback is not recommended
when using the multi interface.
CURLOPT_NOPROGRESS must be set to FALSE to make
this function actually get called.
CURLOPT_PROGRESSDATA
Pass a pointer that will be untouched by libcurl
and passed as the first argument in the progress
callback set with CURLOPT_PROGRESSFUNCTION.
CURLOPT_HEADERFUNCTION
Function pointer that should match the following
prototype: size_t function( void *ptr, size_t size,
size_t nmemb, void *stream);. This function gets
called by libcurl as soon as 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 should
be easy enough 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 stream is the one you set with
the CURLOPT_WRITEHEADER option. The callback func-
tion must return the number of bytes actually taken
care of, or return -1 to signal error to the
library (it will cause it to abort the transfer
with a CURLE_WRITE_ERROR return code).
Since 7.14.1: 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 response-headers mention what header to
expect in the trailer.
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 your own
callback to take care of the writing, this must be
a valid FILE *. See also the CURLOPT_HEADERFUNCTION
option above on how to set a custom get-all-headers
callback.
CURLOPT_DEBUGFUNCTION
Function pointer that should match the following
prototype: int curl_debug_callback (CURL *,
curl_infotype, char *, size_t, void *); CUR-
LOPT_DEBUGFUNCTION replaces the standard debug
function used when CURLOPT_VERBOSE is in effect.
This callback receives debug information, as speci-
fied 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 termi-
nated, but will be exactly of the size as told by
the size_t argument.
Available curl_infotype values:
CURLINFO_TEXT
The data is informational text.
CURLINFO_HEADER_IN
The data is header (or header-like) data
received from the peer.
CURLINFO_HEADER_OUT
The data is header (or header-like) data
sent to the peer.
CURLINFO_DATA_IN
The data is protocol data received from the
peer.
CURLINFO_DATA_OUT
The data is protocol data sent to the peer.
CURLOPT_DEBUGDATA
Pass a pointer to whatever you want passed in to
your CURLOPT_DEBUGFUNCTION in the last void * argu-
ment. This pointer is not used by libcurl, it is
only passed to the callback.
CURLOPT_SSL_CTX_FUNCTION
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 an SSL
connection after having processed all other SSL
related options to give a last chance to an appli-
cation 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 connec-
tions 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.
Using this function allows for example to use
openssl callbacks to add additional validation code
for certificates, and even to change the actual URI
of an 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, other-
wise 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_CONVER-
SIONS 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 con-
vert 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 CUR-
LOPT_CONV_FROM_NETWORK_FUNCTION convert between the
host encoding and the network encoding. They are
used when commands or ASCII data are sent/received
over the network.
CURLOPT_CONV_FROM_UTF8_FUNCTION is called to con-
vert from UTF8 into the host encoding. It is
required only for SSL processing.
If you set a callback pointer to NULL, or don't set
it at all, the built-in libcurl iconv functions
will be used. If HAVE_ICONV was not defined when
libcurl was built, and no callback has been estab-
lished, conversion will return the CURLE_CONV_REQD
error code.
If HAVE_ICONV is defined, CURL_ICONV_CODE-
SET_OF_HOST must also be defined. For example:
#define CURL_ICONV_CODESET_OF_HOST "IBM-1047"
The iconv code in libcurl will default the network
and UTF8 codeset names as follows:
#define CURL_ICONV_CODESET_OF_NETWORK "ISO8859-1"
#define CURL_ICONV_CODESET_FOR_UTF8 "UTF-8"
You will need to override these definitions if they
are different on your system.
ERROR OPTIONS
CURLOPT_ERRORBUFFER
Pass a char * to a buffer that the libcurl may
store human readable error messages in. This may be
more helpful than just the return code from
curl_easy_perform. The buffer must be at least
CURL_ERROR_SIZE big.
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 con-
tents 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 non-zero parameter 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 occa-
sions where non-succesful 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 for when a
"100-continue" is received as a response to a
POST/PUT and a 401 or 407 is received immediately
afterwards.
NETWORK OPTIONS
CURLOPT_URL
The actual URL to deal with. The parameter should
be a char * to a zero terminated string. The string
must remain present until curl no longer needs it,
as it doesn't copy the string.
If the given URL lacks the protocol part ("http://"
or "ftp://" etc), it will attempt to guess which
protocol to use based on the given host name. If
the given protocol of the set URL is not supported,
libcurl will return on error (CURLE_UNSUP-
PORTED_PROTOCOL) when you call curl_easy_perform(3)
or curl_multi_perform(3). Use curl_version_info(3)
for detailed info on which protocols that are sup-
ported.
The string given to CURLOPT_URL must be url-encoded
and following the RFC 2396
(http://curl.haxx.se/rfc/rfc2396.txt).
CURLOPT_URL is the only option that must be set
before curl_easy_perform(3) is called.
CURLOPT_PROXY
Set HTTP proxy to use. The parameter should be a
char * to a zero terminated string holding the host
name or dotted IP address. To specify port number
in this string, append :[port] to the end of the
host name. The proxy string may be prefixed with
[protocol]:// since any such prefix will be
ignored. The proxy's port number may optionally be
specified with the separate option CURLOPT_PROXY-
PORT.
When you tell the library to use an 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 sim-
ilar FTP specifics that don't work unless you tun-
nel through the HTTP proxy. Such tunneling is acti-
vated with CURLOPT_HTTPPROXYTUNNEL.
libcurl respects the environment variables
http_proxy, ftp_proxy, all_proxy etc, if any of
those is set. The CURLOPT_PROXY option does however
override any possibly set environment variables.
Setting the proxy string to "" (an empty string)
will explicitly disable the use of a proxy, even if
there is an environment variable set for it.
Since 7.14.1, the proxy host string given in envi-
ronment variables can be specified the exact same
way as the proxy can be set with CURLOPT_PROXY,
include protocol prefix (http://) and embedded user
+ password.
CURLOPT_PROXYPORT
Pass a long with this option to set the proxy port
to connect to unless it is specified in the proxy
string CURLOPT_PROXY.
CURLOPT_PROXYTYPE
Pass a long with this option to set type of the
proxy. Available options for this are CURL-
PROXY_HTTP, CURLPROXY_SOCKS4 (added in 7.15.2)
CURLPROXY_SOCKS5. The HTTP type is default. (Added
in 7.10)
CURLOPT_HTTPPROXYTUNNEL
Set the parameter to non-zero to get the library to
tunnel all operations through a given HTTP proxy.
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_INTERFACE
Pass a char * as parameter. This set the interface
name to use as outgoing network interface. The name
can be an interface name, an IP address or a host
name.
CURLOPT_LOCALPORT
Pass a long. This sets the local port number of the
socket used for connection. This can be used in
combination with CURLOPT_INTERFACE and you are rec-
ommended to use CURLOPT_LOCALPORTRANGE as well when
this is set. Note that port numbers are only valid
1 - 65535. (Added in 7.15.2)
CURLOPT_LOCALPORTRANGE
Pass a long. This is the number of attempts libcurl
should do 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
value to 1 or below will make libcurl do only one
try for exact port number. Note that port numbers
by nature is a scarce resource that will be busy at
times so setting this value to something too low
might cause unnecessary connection setup failures.
(Added in 7.15.2)
CURLOPT_DNS_CACHE_TIMEOUT
Pass a long, this sets the timeout in seconds. Name
resolves will be kept in memory for this number of
seconds. Set to zero (0) to completely disable
caching, or set to -1 to make the cached entries
remain forever. By default, libcurl caches this
info for 60 seconds.
CURLOPT_DNS_USE_GLOBAL_CACHE
Pass a long. If the value is non-zero, it tells
curl to use a global DNS cache that will survive
between easy handle creations and deletions. This
is not thread-safe and this will use a global vari-
able.
WARNING: this option is considered obsolete. Stop
using it. Switch over to using the share interface
instead! See CURLOPT_SHARE and curl_share_init(3).
CURLOPT_BUFFERSIZE
Pass a long specifying your preferred size (in
bytes) for the receive buffer in libcurl. The main
point of this would be that the write callback gets
called more often and with smaller chunks. This is
just treated as a request, not an order. You cannot
be guaranteed to actually get the given size.
(Added in 7.10)
This size is by default set as big as possible
(CURL_MAX_WRITE_SIZE), so it only makse 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 estab-
lished.
Setting this option will disable TCP's Nagle algo-
rithm. The purpose of this algorithm is to try to
minimize the number of small packets on the network
(where "small packets" means TCP segments less than
the Maximum Segment Size (MSS) for the network).
Maximizing the amount of data sent per TCP segment
is good because it amortizes the overhead of the
send. However, in some cases (most notably telnet
or rlogin) small segments may need to be sent with-
out delay. This is less efficient than sending
larger amounts of data at a time, and can con-
tribute to congestion on the network if overdone.
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 prefer-
ence to any of the options controlled by this
parameter.
Pass a long, set to one of the values described
below.
CURL_NETRC_OPTIONAL
The use of your ~/.netrc file is optional,
and information in the URL is to be pre-
ferred. The file will be scanned with the
host and user name (to find the password
only) or with the host only, to find the
first user name and password after that
machine, which ever information is not spec-
ified in the URL.
Undefined values of the option will have
this effect.
CURL_NETRC_IGNORED
The library will ignore the file and use
only the information in the URL.
This is the default.
CURL_NETRC_REQUIRED
This value tells the library that use of the
file is required, to ignore the information
in the URL, and to search the file with the
host only.
Only machine name, user name and password are taken into
account (init macros and similar things aren't supported).
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 ter-
minated 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 the a .netrc file in
the current user's home directory. (Added in
7.10.9)
CURLOPT_USERPWD
Pass a char * as parameter, which should be [user
name]:[password] to use for the connection. Use
CURLOPT_HTTPAUTH to decide authentication method.
When using NTLM, you can set 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:pass-
word". Some HTTP servers (on Windows) support this
style even for Basic authentication.
When using HTTP and CURLOPT_FOLLOWLOCATION, libcurl
might perform several requests to possibly differ-
ent hosts. libcurl will only send this user and
password information to hosts using the initial
host name (unless CURLOPT_UNRESTRICTED_AUTH is
set), so if libcurl follows locations to other
hosts it will not send the user and password to
those. This is enforced to prevent accidental
information leakage.
CURLOPT_PROXYUSERPWD
Pass a char * as parameter, which should be [user
name]:[password] to use for the connection to the
HTTP proxy. Use CURLOPT_PROXYAUTH to decide
authentication method.
CURLOPT_HTTPAUTH
Pass a long as parameter, which is set to a bit-
mask, to tell libcurl what 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 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_USERPWD option.
(Added in 7.10.6)
CURLAUTH_BASIC
HTTP Basic authentication. This is the
default choice, and the only method that is
in wide-spread use and supported virtually
everywhere. This is sending the user name
and password over the network in plain text,
easily captured by others.
CURLAUTH_DIGEST
HTTP Digest authentication. Digest authen-
tication is defined in RFC2617 and is a more
secure way to do authentication over public
networks than the regular old-fashioned
Basic method.
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 authentica-
tion but may be also used along with another
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 pro-
tocol 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 OpenSSL sup-
port for this option to work, or build
libcurl on Windows.
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.
CURLOPT_PROXYAUTH
Pass a long as parameter, which is set to a bit-
mask, to tell libcurl what 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 pass-
word with the CURLOPT_PROXYUSERPWD option. The bit-
mask 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 non-zero parameter to enable this. When
enabled, libcurl will automatically set the Ref-
erer: field in requests where it follows a Loca-
tion: redirect.
CURLOPT_ENCODING
Sets the contents of the Accept-Encoding: header
sent in an 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 algo-
rithm. If a zero-length string is set, then an
Accept-Encoding: header containing all supported
encodings is sent.
This is a request, not an order; the server may or
may not do it. This option must be set (to any
non-NULL value) or else any unsolicited encoding
done by the server is ignored. See the special file
lib/README.encoding for details.
CURLOPT_FOLLOWLOCATION
A non-zero parameter tells the library to follow
any Location: header that the server sends as part
of an HTTP header.
This means that the library will re-send the same
request on the new location and follow new Loca-
tion: headers all the way until no more such head-
ers are returned. CURLOPT_MAXREDIRS can be used to
limit the number of redirects libcurl will follow.
CURLOPT_UNRESTRICTED_AUTH
A non-zero parameter tells the library it can con-
tinue to send authentication (user+password) when
following locations, even when hostname changed.
This option is meaningful only when setting CUR-
LOPT_FOLLOWLOCATION.
CURLOPT_MAXREDIRS
Pass a long. The set number will be the redirection
limit. If that many redirections have been fol-
lowed, 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_PUT
A non-zero parameter tells the library to use HTTP
PUT to transfer data. The data should be set with
CURLOPT_READDATA and CURLOPT_INFILESIZE.
This option is deprecated and starting with version
7.12.1 you should instead use CURLOPT_UPLOAD.
CURLOPT_POST
A non-zero parameter tells the library to do a reg-
ular HTTP post. This will also make the library use
the a "Content-Type: application/x-www-form-urlen-
coded" header. (This is by far the most commonly
used POST method).
Use the CURLOPT_POSTFIELDS option to specify what
data to post and CURLOPT_POSTFIELDSIZE to set the
data size.
Optionally, you can provide data to POST using the
CURLOPT_READFUNCTION and CURLOPT_READDATA options
but then you must make sure to not set CUR-
LOPT_POSTFIELDS to anything but NULL. When provid-
ing data with a callback, you must transmit it
using chunked transfer-encoding or you must set the
size of the data with the CURLOPT_POSTFIELDSIZE
option.
You can override the default POST Content-Type:
header by setting your own with CURLOPT_HTTPHEADER.
Using POST with HTTP 1.1 implies the use of a
"Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
If you use POST to a HTTP 1.1 server, you can send
data without knowing the size before starting the
POST if you use chunked encoding. You enable this
by adding a header like "Transfer-Encoding: chun-
ked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or
without chunked transfer, you must specify the size
in the request.
When setting CURLOPT_POST to a non-zero value, it
will automatically set CURLOPT_NOBODY to 0 (since
7.14.1).
If you issue a POST request and then want to make a
HEAD or GET using the same re-used handle, you must
explictly set the new request type using CUR-
LOPT_NOBODY or CURLOPT_HTTPGET or similar.
CURLOPT_POSTFIELDS
Pass a char * as parameter, which should be the
full data to post in an 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. Take note.
This POST is a normal application/x-www-form-urlen-
coded 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 CUR-
LOPT_POST.
Using POST with HTTP 1.1 implies the use of a
"Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
To make multipart/formdata posts (aka
rfc1867-posts), check out the CURLOPT_HTTPPOST
option.
CURLOPT_POSTFIELDSIZE
If you want to post data to the server without let-
ting 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 other-
wise is likely to fail. If this size is set to -1,
the library will use strlen() to get the size.
CURLOPT_POSTFIELDSIZE_LARGE
Pass a curl_off_t as parameter. Use this to set the
size of the CURLOPT_POSTFIELDS data to prevent
libcurl from doing strlen() on the data to figure
out the size. This is the large file version of the
CURLOPT_POSTFIELDSIZE option. (Added in 7.11.1)
CURLOPT_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 easi-
est way to create such a list, is to use curl_for-
madd(3) as documented. The data in this list must
remain intact until you close this curl handle
again with curl_easy_cleanup(3).
Using POST with HTTP 1.1 implies the use of a
"Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
When setting CURLOPT_HTTPPOST, it will automati-
cally set CURLOPT_NOBODY to 0 (since 7.14.1).
CURLOPT_REFERER
Pass a pointer to a zero terminated string as
parameter. It will be used to set the Referer:
header in the http request sent to the remote
server. This can be used to fool servers or
scripts. You can also set any custom header with
CURLOPT_HTTPHEADER.
CURLOPT_USERAGENT
Pass a pointer to a zero terminated string as
parameter. It will be used to set the User-Agent:
header in the http request sent to the remote
server. This can be used to fool servers or
scripts. You can also set any custom header with
CURLOPT_HTTPHEADER.
CURLOPT_HTTPHEADER
Pass a pointer to a linked list of HTTP headers to
pass to the server in your HTTP request. The linked
list should be a fully valid list of struct
curl_slist structs properly filled in. Use
curl_slist_append(3) to create the list and
curl_slist_free_all(3) to clean up an entire list.
If you add a header that is otherwise generated and
used by libcurl internally, your added one will be
used instead. If you add a header with no contents
as in 'Accept:' (no data on the right side of the
colon), the internally used header will get dis-
abled. Thus, using this option you can add new
headers, replace internal headers and remove inter-
nal headers. To add a header with no contents, make
the contents be two quotes: "". The headers
included in the linked list must not be CRLF-termi-
nated, 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 fol-
lowing 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. So if your alias is "MYHTTP/9.9", Libcurl
will not treat the server as responding with HTTP
version 9.9. Instead Libcurl will use the value
set by option CURLOPT_HTTP_VERSION.
CURLOPT_COOKIE
Pass a pointer to a zero terminated string as
parameter. It will be used to set a cookie in the
http request. The format of the string should be
NAME=CONTENTS, where NAME is the cookie name and
CONTENTS is what the cookie should contain.
If you need to set 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.
Using this option multiple times will only make the
latest string override the previously ones.
CURLOPT_COOKIEFILE
Pass a pointer to a zero terminated string as
parameter. It should contain the name of your file
holding cookie data to read. The cookie data may be
in Netscape / Mozilla cookie data format or just
regular HTTP-style headers dumped to a file.
Given an empty or non-existing file or by passing
the empty string (""), this option will enable
cookies for this curl handle, making it understand
and parse received cookies and then use matching
cookies in future request.
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 CURLOPT_DEBUGFUNC-
TION 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 non-zero 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, inde-
pendent if they are session cookies are not. Ses-
sion cookies are cookies without expiry date and
they are meant to be alive and existing for this
"session" only.
CURLOPT_COOKIELIST
Pass a char * to a cookie string. Cookie can be
either in Netscape / Mozilla format or just regular
HTTP-style header (Set-Cookie: ...) format. If cURL
cookie engine was not enabled it will enable its
cookie engine. Passing a magic string "ALL" will
erase all cookies known by cURL. (Added in 7.14.1)
Passing the special string "SESS" will only erase
all session cookies known by cURL. (Added in
7.15.4)
CURLOPT_HTTPGET
Pass a long. If the long is non-zero, this forces
the HTTP request to get back to GET. usable if a
POST, HEAD, PUT or a custom request have been used
previously using the same curl handle.
When setting CURLOPT_HTTPGET to a non-zero value,
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 connec-
tion. (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. Note however that 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)
FTP OPTIONS
CURLOPT_FTPPORT
Pass a pointer to a zero terminated string as
parameter. It will be used to get the IP address to
use for the ftp PORT instruction. The PORT instruc-
tion tells the remote server to connect to our
specified IP address. The string may be a plain IP
address, a host name, an network interface name
(under Unix) or just a '-' letter to let the
library use your systems default IP address.
Default FTP operations are passive, and thus won't
use PORT.
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 commands to
pass to the server prior to your ftp request. This
will be done before any other FTP commands are
issued (even before the CWD command). The linked
list should be a fully valid list of to append
strings (commands) to the list, and clear the
entire list afterwards with curl_slist_free_all(3).
Disable this operation again by setting a NULL to
this option.
CURLOPT_POSTQUOTE
Pass a pointer to a linked list of FTP commands to
pass to the server after your ftp transfer request.
The linked list should be a fully valid list of
struct curl_slist structs properly filled in as
described for CURLOPT_QUOTE. Disable this operation
again by setting a NULL to this option.
CURLOPT_PREQUOTE
Pass a pointer to a linked list of FTP commands to
pass to the server after the transfer type is set.
The linked list should be a fully valid list of
struct curl_slist structs properly filled in as
described for CURLOPT_QUOTE. Disable this operation
again by setting a NULL to this option. Before ver-
sion 7.15.6, if you also set CURLOPT_NOBODY non-
zero, this option didn't work.
CURLOPT_FTPLISTONLY
A non-zero parameter tells the library to just list
the names of an ftp directory, instead of doing a
full directory listing that would include file
sizes, dates etc.
This causes an FTP NLST command to be sent. Beware
that some FTP servers list only files in their
response to NLST; they might not include subdirec-
tories and symbolic links.
CURLOPT_FTPAPPEND
A non-zero parameter tells the library to append to
the remote file instead of overwrite it. This is
only useful when uploading to an ftp site.
CURLOPT_FTP_USE_EPRT
Pass a long. If the value is non-zero, it tells
curl to use the EPRT (and LPRT) command when doing
active FTP downloads (which is enabled by CUR-
LOPT_FTPPORT). Using EPRT means that it will first
attempt to use EPRT and then LPRT before using
PORT, but if you pass FALSE (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 non-zero, it tells
curl to use the EPSV command when doing passive FTP
downloads (which it always does by default). Using
EPSV means that it will first attempt to use EPSV
before using PASV, but if you pass FALSE (zero) to
this option, it will not try using EPSV, only plain
PASV.
If the server is an IPv6 host, this option will
have no effect as of 7.12.3.
CURLOPT_FTP_CREATE_MISSING_DIRS
Pass a long. If the value is non-zero, 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)
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 consid-
ered hung. While curl is waiting for a response,
this value overrides CURLOPT_TIMEOUT. It is recom-
mended that if used in conjunction with CUR-
LOPT_TIMEOUT, you set CURLOPT_FTP_RESPONSE_TIMEOUT
to a value smaller than CURLOPT_TIMEOUT. (Added in
7.10.8)
CURLOPT_FTP_ALTERNATIVE_TO_USER
Pass a char * as parameter, pointing to a string
which will be used to authenticate if the usual FTP
"USER user" and "PASS password" negotiation fails.
This is currently only known to be required when
connecting to Tumbleweed's Secure Transport FTPS
server using client certificates for authentica-
tion. (Added in 7.15.5)
CURLOPT_FTP_SKIP_PASV_IP
Pass a long. If set to a non-zero value, 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 connec-
tion. 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_FTP_SSL
Pass a long using one of the values from below, to
make libcurl use your desired level of SSL for the
ftp transfer. (Added in 7.11.0)
CURLFTPSSL_NONE
Don't attempt to use SSL.
CURLFTPSSL_TRY
Try using SSL, proceed as normal otherwise.
CURLFTPSSL_CONTROL
Require SSL for the control connection or
fail with CURLE_FTP_SSL_FAILED.
CURLFTPSSL_ALL
Require SSL for all communication or fail
with CURLE_FTP_SSL_FAILED.
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 CUR-
LOPT_FTP_SSL). (Added in 7.12.2)
CURLFTPAUTH_DEFAULT
Allow libcurl to decide
CURLFTPAUTH_SSL
Try "AUTH SSL" first, and only if that fails
try "AUTH TLS"
CURLFTPAUTH_TLS
Try "AUTH TLS" first, and only if that fails
try "AUTH SSL"
CURLOPT_FTP_SSL_CCC
If enabled, this option makes libcurl use CCC
(Clear Command Channel). It shuts down the SSL/TLS
layer after authenticating. The rest of the control
channel communication will be unencrypted. This
allows NAT routers to follow the FTP transaction.
Pass a long using one of the values below. (Added
in 7.16.1)
CURLFTPSSL_CCC_NONE
Don't attempt to use CCC.
CURLFTPSSL_CCC_PASSIVE
Do not initiate the shutdown, but wait for
the server to do it. Do not send a reply.
CURLFTPSSL_CCC_ACTIVE
Initiate the shutdown and wait for a reply.
CURLOPT_FTP_ACCOUNT
Pass a pointer to a zero-terminated string (or NULL
to disable). When an FTP server asks for "account
data" after user name and password has been pro-
vided, this data is sent off using the ACCT com-
mand. (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 alterna-
tives:
CURLFTPMETHOD_MULTICWD
libcurl does a single CWD operation for each
path part in the given URL. For deep hierar-
chies this means very many commands. This is
how RFC1738 says it should be done. This is
the default but the slowest behavior.
CURLFTPMETHOD_NOCWD
libcurl does no CWD at all. libcurl will do
SIZE, RETR, STOR etc and give a full path to
the server for all these commands. This is
the fastest behavior.
CURLFTPMETHOD_SINGLECWD
libcurl does one CWD with the full target
directory and then operates on the file
"normally" (like in the multicwd case). This
is somewhat more standards compliant than
'nocwd' but without the full penalty of
'multicwd'.
PROTOCOL OPTIONS
CURLOPT_TRANSFERTEXT
A non-zero parameter tells the library to use ASCII
mode for ftp transfers, instead of the default
binary transfer. For win32 systems it does not set
the stdout to binary mode. This option can be
usable when transferring text data between systems
with different views on certain characters, such as
newlines or similar.
libcurl does not do a complete ASCII conversion
when doing ASCII transfers over FTP. This is a
known limitation/flaw that nobody has rectified.
libcurl simply sets the mode to ascii and performs
a standard transfer.
CURLOPT_CRLF
Convert Unix newlines to CRLF newlines on trans-
fers.
CURLOPT_RANGE
Pass a char * as parameter, which should contain
the specified range you want. It should be in the
format "X-Y", where X or Y may be left out. HTTP
transfers also support several intervals, separated
with commas as in "X-Y,N-M". Using this kind of
multiple intervals will cause the HTTP server to
send the response document in pieces (using stan-
dard MIME separation techniques). Pass a NULL to
this option to disable the use of ranges.
CURLOPT_RESUME_FROM
Pass a long as parameter. It contains the offset in
number of bytes that you want the transfer to start
from. Set this option to 0 to make the transfer
start from the beginning (effectively disabling
resume). For FTP, set this option to -1 to make the
transfer start from the end of the target file
(useful to continue an interrupted upload).
CURLOPT_RESUME_FROM_LARGE
Pass a curl_off_t as parameter. It contains the
offset in number of bytes that you want the trans-
fer to start from. (Added in 7.11.0)
CURLOPT_CUSTOMREQUEST
Pass a pointer to a zero terminated string as
parameter. It will be user instead of GET or HEAD
when doing an HTTP request, or instead of LIST or
NLST when doing an ftp directory listing. This is
useful for doing DELETE or other more or less
obscure HTTP requests. Don't do this at will, make
sure your server supports the command first.
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, includ-
ing multiple headers and POST contents. While that
might work in many cases, it will cause libcurl to
send invalid requests and it could possibly confuse
the remote server badly. Use CURLOPT_POST and CUR-
LOPT_POSTFIELDS to set POST data. Use CURLOPT_HTTP-
HEADER to replace or extend the set of headers sent
by libcurl. Use CURLOPT_HTTP_VERSION to change HTTP
version.
CURLOPT_FILETIME
Pass a long. If it is a non-zero value, libcurl
will attempt to get the modification date of the
remote document in this operation. This requires
that the remote server sends the time or replies to
a time querying command. The curl_easy_getinfo(3)
function with the CURLINFO_FILETIME argument can be
used after a transfer to extract the received time
(if any).
CURLOPT_NOBODY
A non-zero parameter tells the library to not
include the body-part in the output. This is only
relevant for protocols that have separate header
and body parts. On HTTP(S) servers, this will make
libcurl do a HEAD request.
To change request to GET, you should use CUR-
LOPT_HTTPGET. Change request to POST with CUR-
LOPT_POST etc.
CURLOPT_INFILESIZE
When uploading a file to a remote site, this option
should be used to tell libcurl what the expected
size of the infile is. This value should be passed
as a long. See also CURLOPT_INFILESIZE_LARGE.
Note that 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)
Note that 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 non-zero parameter tells the library to prepare
for an upload. The CURLOPT_READDATA and CUR-
LOPT_INFILESIZE or CURLOPT_INFILESIZE_LARGE options
are also interesting for uploads. If the protocol
is HTTP, uploading means using the PUT request
unless you tell libcurl otherwise.
Using PUT with HTTP 1.1 implies the use of a
"Expect: 100-continue" header. You can disable
this header with CURLOPT_HTTPHEADER as usual.
If you use PUT to a HTTP 1.1 server, you can upload
data without knowing the size before starting the
transfer if you use chunked encoding. You enable
this by adding a header like "Transfer-Encoding:
chunked" with CURLOPT_HTTPHEADER. With HTTP 1.0 or
without chunked transfer, you must specify the
size.
CURLOPT_MAXFILESIZE
Pass a long as parameter. This allows you to spec-
ify the maximum size (in bytes) of a file to down-
load. If the file requested is larger than this
value, the transfer will not start and CURLE_FILE-
SIZE_EXCEEDED will be returned.
The file size is not always known prior to down-
load, 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_FILE-
SIZE_EXCEEDED will be returned. (Added in 7.11.0)
The file size is not always known prior to down-
load, 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 CUR-
LOPT_TIMEVALUE time value is treated. You can set
this parameter to CURL_TIMECOND_IFMODSINCE or
CURL_TIMECOND_IFUNMODSINCE. This feature applies to
HTTP and FTP.
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
have not been met.
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_TIME-
CONDITION.
CONNECTION OPTIONS
CURLOPT_TIMEOUT
Pass a long as parameter containing the maximum
time in seconds that you allow the libcurl transfer
operation to take. Normally, name lookups can take
a considerable time and limiting operations to less
than a few minutes risk aborting perfectly normal
operations. This option will cause curl to use the
SIGALRM to enable time-outing system calls.
In unix-like systems, this might cause signals to
be used unless CURLOPT_NOSIGNAL is set.
CURLOPT_TIMEOUT_MS
Like CURLOPT_TIMEOUT but takes number of millisec-
onds instead. If libcurl is built to use the stan-
dard system name resolver, that part will still use
full-second resolution for timeouts. (Added in
7.16.2)
CURLOPT_LOW_SPEED_LIMIT
Pass a long as parameter. It contains the transfer
speed in bytes per second that the transfer should
be below during CURLOPT_LOW_SPEED_TIME seconds for
the library to consider it too slow and abort.
CURLOPT_LOW_SPEED_TIME
Pass a long as parameter. It contains the time in
seconds that the transfer should be below the CUR-
LOPT_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 on cumulative average during the
transfer, the transfer will pause to keep the aver-
age 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 on cumulative average during the
transfer, the transfer will pause to keep the aver-
age rate less than or equal to the parameter value.
Defaults to unlimited speed. (Added in 7.15.5)
CURLOPT_MAXCONNECTS
Pass a long. The set number will be the persistent
connection cache size. The set amount will be the
maximum amount of simultaneously open connections
that libcurl may cache. Default is 5, and there
isn't much point in changing this value unless you
are perfectly aware of how this work and changes
libcurl's behaviour. This concerns connection using
any of the protocols that support persistent con-
nections.
When reaching the maximum limit, curl closes the
oldest one in the cache to prevent the number of
open connections to increase.
If you already have performed transfers with this
curl handle, setting a smaller MAXCONNECTS than
before may cause open connections to get closed
unnecessarily.
CURLOPT_CLOSEPOLICY
(Obsolete) This option does nothing.
CURLOPT_FRESH_CONNECT
Pass a long. Set to non-zero to make the next
transfer use a new (fresh) connection by force. If
the connection cache is full before this connec-
tion, one of the existing connections will be
closed as according to the selected or default pol-
icy. 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 con-
nection (default behavior).
CURLOPT_FORBID_REUSE
Pass a long. Set to non-zero to make the next
transfer explicitly close the connection when done.
Normally, libcurl keep all connections alive when
done with one transfer in case there comes a suc-
ceeding one that can re-use them. This option
should be used with caution and only if you under-
stand what it does. Set to 0 to have libcurl keep
the connection open for possibly later re-use
(default behavior).
CURLOPT_CONNECTTIMEOUT
Pass a long. It should contain the maximum time in
seconds that you allow the connection to the server
to take. This only limits the connection phase,
once it has connected, this option is of no more
use. Set to zero to disable connection timeout (it
will then only timeout on the system's internal
timeouts). 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 number of
milliseconds instead. If libcurl is built to use
the standard system name resolver, that part will
still use full-second resolution for timeouts.
(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 ver-
sions that your system allows.
CURL_IPRESOLVE_V4
Resolve to ipv4 addresses.
CURL_IPRESOLVE_V6
Resolve to ipv6 addresses.
CURLOPT_CONNECT_ONLY
Pass a long. A non-zero parameter tells the library
to perform any required proxy authentication and
connection setup, but no data transfer.
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)
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 is the nickname of the certificate
you wish to authenticate with.
CURLOPT_SSLCERTTYPE
Pass a pointer to a zero terminated string as
parameter. The string should be the format of your
certificate. Supported formats are "PEM" and "DER".
(Added in 7.9.3)
CURLOPT_SSLCERTPASSWD
Pass a pointer to a zero terminated string as
parameter. It will be used as the password required
to use the CURLOPT_SSLCERT certificate.
This option is replaced by CURLOPT_SSLKEYPASSWD and
should only be used for backward compatibility. You
never needed a pass phrase to load a certificate
but you need one to load your private key.
CURLOPT_SSLKEY
Pass a pointer to a zero terminated string as
parameter. The string should be the file name of
your private key. The default format is "PEM" and
can be changed with CURLOPT_SSLKEYTYPE.
CURLOPT_SSLKEYTYPE
Pass a pointer to a zero terminated string as
parameter. The string should be the format of your
private key. Supported formats are "PEM", "DER" and
"ENG".
The format "ENG" enables you to load the private
key from a crypto engine. In this case CUR-
LOPT_SSLKEY is used as an identifier passed to the
engine. You have to set the crypto engine with CUR-
LOPT_SSLENGINE. "DER" format key file currently
does not work because of a bug in OpenSSL.
CURLOPT_SSLKEYPASSWD
Pass a pointer to a zero terminated string as
parameter. It will be used as the password required
to use the CURLOPT_SSLKEY or CURLOPT_SSH_PRI-
VATE_KEYFILE private key.
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.
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. When libcurl built with
OpenSSL or NSS, this will attempt to figure
out the remote SSL protocol version. Unfor-
tunately there are a lot of ancient and bro-
ken servers in use which cannot handle this
technique and will fail to connect. When
libcurl is built with GnuTLS, this will mean
SSLv3.
CURL_SSLVERSION_TLSv1
Force TLSv1
CURL_SSLVERSION_SSLv2
Force SSLv2
CURL_SSLVERSION_SSLv3
Force SSLv3
CURLOPT_SSL_VERIFYPEER
Pass a long as parameter.
This option determines whether curl verifies the
authenticity of the peer's certificate. A nonzero
value means curl verifies; zero means it doesn't.
The default is nonzero, but before 7.10, it was
zero.
When negotiating an SSL connection, the server
sends a certificate indicating its identity. Curl
verifies whether the certificate is authentic, i.e.
that you can trust that the server is who the cer-
tificate says it is. This trust is based on a
chain of digital signatures, rooted in certifica-
tion authority (CA) certificates you supply. As of
7.10, curl installs a default bundle of CA certifi-
cates and you can specify alternate certificates
with the CURLOPT_CAINFO option or the CURLOPT_CAP-
ATH 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 connection succeeds regardless.
Authenticating the certificate is not by itself
very useful. You typically want to ensure that the
server, as authentically identified by its certifi-
cate, is the server you mean to be talking to. Use
CURLOPT_SSL_VERIFYHOST to control that.
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 com-
bination with the CURLOPT_SSL_VERIFYPEER option.
If CURLOPT_SSL_VERIFYPEER is zero, CURLOPT_CAINFO
need not even indicate an accessible file.
Note that 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 certificate database resides in.
CURLOPT_CAPATH
Pass a char * to a zero terminated string naming a
directory holding multiple CA certificates to ver-
ify the peer with. The certificate directory must
be prepared using the openssl c_rehash utility.
This makes sense only when used in combination with
the CURLOPT_SSL_VERIFYPEER option. If CUR-
LOPT_SSL_VERIFYPEER is zero, CURLOPT_CAPATH need
not even indicate an accessible path. The CUR-
LOPT_CAPATH function apparently does not work in
Windows due to some limitation in openssl. This
option is OpenSSL-specific and does nothing if
libcurl is built to use GnuTLS.
CURLOPT_RANDOM_FILE
Pass a char * to a zero terminated file name. The
file will be used to read from to seed the random
engine for SSL. The more random the specified file
is, the more secure the SSL connection will become.
CURLOPT_EGDSOCKET
Pass a char * to the zero terminated path name to
the Entropy Gathering Daemon socket. It will be
used to seed the random engine for SSL.
CURLOPT_SSL_VERIFYHOST
Pass a long as parameter.
This option determines whether libcurl verifies
that the server cert is for the server it is known
as.
When negotiating an SSL connection, the server
sends a certificate indicating its identity.
When CURLOPT_SSL_VERIFYHOST is 2, that certificate
must indicate that the server is the server to
which you meant to connect, or the connection
fails.
Curl considers the server the intended one when the
Common Name field or a Subject Alternate Name field
in the certificate matches the host name in the URL
to which you told Curl to connect.
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 set-
ting).
When the value is 0, the connection succeeds
regardless of the names in the certificate.
The default, since 7.10, is 2.
The checking this option controls is of the iden-
tity that the server claims. The server could be
lying. To control lying, see CURLOPT_SSL_VERI-
FYPEER.
CURLOPT_SSL_CIPHER_LIST
Pass a char *, pointing to a zero terminated string
holding the list of ciphers to use for the SSL con-
nection. 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.red-
hat.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.
Note that 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_KRB4LEVEL
Pass a char * as parameter. Set the krb4 security
level, this also enables krb4 awareness. This is a
string, 'clear', 'safe', 'confidential' or 'pri-
vate'. If the string is set but doesn't match one
of these, 'private' will be used. Set the string to
NULL to disable kerberos4. The kerberos support
only works for FTP.
SSH OPTIONS
CURLOPT_SSH_AUTH_TYPES
Pass a long set to a bitmask consisting of one or
more of CURLSSH_AUTH_PUBLICKEY, CURLSSH_AUTH_PASS-
WORD, CURLSSH_AUTH_HOST, CURLSSH_AUTH_KEYBOARD. Set
CURLSSH_AUTH_ANY to let libcurl pick one.
CURLOPT_SSH_PUBLIC_KEYFILE
Pass a char * pointing to a file name for your pub-
lic key. If not used, libcurl defaults to using
~/.ssh/id_dsa.pub.
CURLOPT_SSH_PRIVATE_KEYFILE
Pass a char * pointing to a file name for your pri-
vate key. If not used, libcurl defaults to using
~/.ssh/id_dsa. If the file is password-protected,
set the password with CURLOPT_SSLKEYPASSWD.
OTHER OPTIONS
CURLOPT_PRIVATE
Pass a char * as parameter, pointing to data that
should be associated with this curl handle. The
pointer can subsequently be retrieved using
curl_easy_getinfo(3) with the CURLINFO_PRIVATE
option. libcurl itself does nothing with this data.
(Added in 7.10.3)
CURLOPT_SHARE
Pass a share handle as a parameter. The share han-
dle 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 han-
dle instead of keeping the data to itself. This
enables several curl handles to share data. If the
curl handles are used simultaneously, you MUST use
the locking methods in the share handle. See
curl_share_setopt(3) for details.
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 . 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 defines.
See the libcurl-errors(3) man page for the full list with
descriptions.
If you try to set an option that libcurl doesn't know
about, perhaps because the library is too old to support
it or the option was removed in a recent version, this
function will return CURLE_FAILED_INIT.
SEE ALSO
curl_easy_init(3), curl_easy_cleanup(3),
curl_easy_reset(3),