curleasysetopt(3) libcurl Manual curleasysetopt(3)
NAME
curleasysetopt - set options for a curl easy handle
SYNOPSIS
#include
CURLcode curleasysetopt(CURL *handle, CURLoption option, parameter);
DESCRIPTION
curleasysetopt() is used to tell libcurl how to behave. By using the
appropriate options to curleasysetopt, 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 curlofft, 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 curleasysetopt() 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
curleasyreset(3).
NOTE:: strings passed to libcurl as 'char *' arguments, will not be
copied by the library. Instead you should keep them available until
libcurl no longer needs them. Failing to do so will cause very odd
behavior or even crashes. libcurl will need them until you call
curleasycleanup(3) or you set the same option again to use a differ-
ent pointer.
The handle is the return code from a curleasyinit(3) or
curleasyduphandle(3) call.
BEHAVIOR OPTIONS
CURLOPTVERBOSE
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
information will be sent to stderr, or the stream set with CUR-
LOPTSTDER.
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 CURLOPTDEBUGFUNCTION.
CURLOPTHEADER
A non-zero parameter 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 HTP).
CURLOPTNOPROGRES
A non-zero parameter tells the library to shut off the built-in
progress meter completely.
NOTE:: future versions of libcurl is likely to not have any
built-in progress meter at all.
CURLOPTNOSIGNAL
Pass a long. If it is non-zero, libcurl will not use any func-
tions 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)
Consider building libcurl with ares support to enable asynchro-
nous DNS lookups. It enables nice timeouts for name resolves
without signals.
CALBACK OPTIONS
CURLOPTWRITEFUNCTION
Function pointer that should match the following prototype:
sizet function( void **ptr,, sizet size,, sizet 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 differs from the amount passed to your func-
tion, it'll signal an error to the library and it will abort the
transfer and return CURLEWRITEROR.
This function may be called with zero bytes data if the trans-
fered file is empty.
Set the stream argument with the CURLOPTWRITEDATA option.
NOTE:: you will be passed as much data as possible in all
invokes, but you cannot possibly make any assumptions. It may be
one byte, it may be thousands. The maximum amount of data that
can be passed to the write callback is defined in the curl.h
header file: CURLMAXWRITESIZE.
CURLOPTWRITEDATA
Data pointer to pass to the file write function. Note that if
you specify the CURLOPTWRITEFUNCTION, this is the pointer
you'll get as input. If you don't use a callback, you must pass
a 'FILE *' as libcurl will pass this to fwrite() when writing
data.
NOTE:: If you're using libcurl as a win32 DL, you MUST use the
CURLOPTWRITEFUNCTION if you set this option or you will experi-
ence crashes.
This option is also known with the older name CURLOPTFILE, the
name CURLOPTWRITEDATA was introduced in 7.9.7.
CURLOPTREADFUNCTION
Function pointer that should match the following prototype:
sizet function( void **ptr,, sizet size,, sizet nmemb,, void
**stream);; This function gets called by libcurl as soon as it
needs to read data in order to send it to the peer. The data
area pointed at by the pointer ptr may be filled with at most
size multiplied with nmemb number of bytes. Your function must
return the actual number of bytes that you stored in that memory
area. Returning 0 will signal end-of-file to the library and
cause it to stop the current transfer.
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.
In libcurl 7.12.1 and later, the read callback may return
CURLREADFUNCABORT to stop the current operation at once, with
a CURLEABORTEDBYCALBACK error code from the transfer.
CURLOPTREADATA
Data pointer to pass to the file read function. Note that if you
specify the CURLOPTREADFUNCTION, this is the pointer you'll get
as input. If you don't specify a read callback, this must be a
valid FILE *.
NOTE:: If you're using libcurl as a win32 DL, you MUST use a
CURLOPTREADFUNCTION if you set this option.
This option is also known with the older name CURLOPTINFILE,
the name CURLOPTREADATA was introduced in 7.9.7.
CURLOPTIOCTLFUNCTION
Function pointer that should match the curlioctlcallback pro-
totype 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 HTP PUT or POST
with a multi-pass authentication method. (Opion added in
7.12.3)
CURLOPTIOCTLDATA
Pass a pointer that will be untouched by libcurl and passed as
the 3rd argument in the ioctl callback set with CURLOPTIOCTL-
FUNCTION. (Option added in 7.12.3)
CURLOPTPROGRESFUNCTION
Function pointer that should match the curlprogresscallback
prototype found in . This function gets called by
libcurl instead of its internal equivalent with a frequent
interval during data transfer. Unknown/unused argument values
will be set to zero (like if you only download data, the upload
size will remain 0). Returning a non-zero value from this call-
back will cause libcurl to abort the transfer and return
CURLEABORTEDBYCALBACK.
Also note that CURLOPTNOPROGRES must be set to FALSE to make
this function actually get called.
CURLOPTPROGRESDATA
Pass a pointer that will be untouched by libcurl and passed as
the first argument in the progress callback set with CUR-
LOPTPROGRESFUNCTION.
CURLOPTHEADERFUNCTION
Function pointer that should match the following prototype:
sizet function( void *ptr, sizet size, sizet nmemb, void
*stream);. This function gets called by libcurl as soon as there
is received header data that needs to be written down. The head-
ers are guaranteed to be written one-by-one and only complete
lines are written. Parsing headers should be easy enough using
this. The size of the data pointed to by ptr is size multiplied
with nmemb. The pointer named stream will be the one you passed
to libcurl with the CURLOPTWRITEHEADER option. Return the num-
ber of bytes actually written or return -1 to signal error to
the library (it will cause it to abort the transfer with a
CURLEWRITEROR return code).
CURLOPTWRITEHEADER
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
CURLOPTHEADERFUNCTION option above on how to set a custom get-
all-headers callback.
CURLOPTDEBUGFUNCTION
Function pointer that should match the following prototype: int
curldebugcallback (CURL *, curlinfotype, char *, sizet, void
*); CURLOPTDEBUGFUNCTION replaces the standard debug function
used when CURLOPTVERBOSE is in effect. This callback receives
debug information, as specified with the curlinfotype argument.
This function must return 0. The data pointed to by the char *
passed to this function WIL NOT be zero terminated, but will be
exactly of the size as told by the sizet argument.
Available curlinfotype values:
CURLINFOTEXT
The data is informational text.
CURLINFOHEADERIN
The data is header (or header-like) data received from
the peer.
CURLINFOHEADEROUT
The data is header (or header-like) data sent to the
peer.
CURLINFODATAIN
The data is protocol data received from the peer.
CURLINFODATAOUT
The data is protocol data sent to the peer.
CURLOPTDEBUGDATA
Pass a pointer to whatever you want passed in to your CUR-
LOPTDEBUGFUNCTION in the last void * argument. This pointer is
not used by libcurl, it is only passed to the callback.
CURLOPTSLCTXFUNCTION
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 SL connection after having processed all other SL
related options to give a last chance to an application to mod-
ify the behaviour of openssl's ssl initialization. The sslctx
parameter is actually a pointer to an openssl SLCTX. 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 CUR-
LOPTSLCTXDATA option. This option was introduced in 7.11.0.
NOTE:: 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 valida-
tion code for certificates, and even to change the actual URI of
an HTPS request (example used in the lib509 test case). See
also the example section for a replacement of the key, certifi-
cate and trust file settings.
CURLOPTSLCTXDATA
Data pointer to pass to the ssl context callback set by the
option CURLOPTSLCTXFUNCTION, this is the pointer you'll get
as third parameter, otherwise NUL. (Added in 7.11.0)
EROR OPTIONS
CURLOPTERORBUFER
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 the library. The buffer must be at least
CURLERORSIZE big.
Use CURLOPTVERBOSE and CURLOPTDEBUGFUNCTION to better
debug/trace why errors happen.
Note:: if the library does not return an error, the buffer may
not have been touched. Do not rely on the contents in those
cases.
CURLOPTSTDER
Pass a FILE * as parameter. Tell libcurl to use this stream
instead of stderr when showing the progress meter and displaying
CURLOPTVERBOSE data.
CURLOPTFAILONEROR
A non-zero parameter tells the library to fail silently if the
HTP code returned is equal to or larger than 300. The default
action would be to return the page normally, ignoring that code.
NETWORK OPTIONS
CURLOPTURL
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 (CURLEUNSUPORTEDPRO-
TOCOL) when you call curleasyperform(3) or curlmultiper-
form(3). Use curlversioninfo(3) for detailed info on which
protocols that are supported.
NOTE:: CURLOPTURL is the only option that must be set before
curleasyperform(3) is called.
CURLOPTPROXY
Set HTP 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 CURLOPTPROXYPORT.
NOTE:: when you tell the library to use an HTP proxy, libcurl
will transparently convert operations to HTP even if you spec-
ify an FTP URL etc. This may have an impact on what other fea-
tures of the library you can use, such as CURLOPTQUOTE and sim-
ilar FTP specifics that don't work unless you tunnel through the
HTP proxy. Such tunneling is activated with CURLOPTHTPROXY-
TUNEL.
NOTE2:: libcurl respects the environment variables httpproxy,
ftpproxy, allproxy etc, if any of those is set.
CURLOPTPROXYPORT
Pass a long with this option to set the proxy port to connect to
unless it is specified in the proxy string CURLOPTPROXY.
CURLOPTPROXYTYPE
Pass a long with this option to set type of the proxy. Available
options for this are CURLPROXYHTP and CURLPROXYSOCKS5, with
the HTP one being default. (Added in 7.10)
CURLOPTHTPROXYTUNEL
Set the parameter to non-zero to get the library to tunnel all
operations through a given HTP proxy. Note that there is a big
difference between using a proxy and to tunnel through it. If
you don't know what this means, you probably don't want this
tunneling option.
CURLOPTINTERFACE
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.
CURLOPTDNSCACHETIMEOUT
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.
CURLOPTDNSUSEGLOBALCACHE
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 variable.
WARNING:: this option is considered obsolete. Stop using it.
Switch over to using the share interface instead! See CUR-
LOPTSHARE and curlshareinit(3).
CURLOPTBUFERSIZE
Pass a long specifying your preferred size for the receive
buffer in libcurl. The main point of this would be that the
write callback gets called more often and with smaller chunks.
This is just treated as a request, not an order. You cannot be
guaranteed to actually get the given size. (Added in 7.10)
CURLOPTPORT
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.
CURLOPTCPNODELAY
Pass a long specifying whether the TCPNODELAY 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 (MS) 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.
NAMES and PASWORDS OPTIONS (Authentication)
CURLOPTNETRC
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 CURLOPTURL.
Note:: libcurl uses a user name (and supplied or prompted pass-
word) supplied with CURLOPTUSERPWD in preference to any of the
options controlled by this parameter.
Pass a long, set to one of the values described below.
CURLNETRCOPTIONAL
The use of your ~/.netrc file is optional, and informa-
tion in the URL is to be preferred. The file will be
scanned with the host and user name (to find the password
only) or with the host only, to find the first user name
and password after that machine, which ever information
is not specified in the URL.
Undefined values of the option will have this effect.
CURLNETRCIGNORED
The library will ignore the file and use only the infor-
mation in the URL.
This is the default.
CURLNETRCREQUIRED
This value tells the library that use of the file is
required, to ignore the information in the URL, and to
search the file with the host only.
Only machine name, user name and password are taken into account (init
macros and similar things aren't supported).
Note:: libcurl does not verify that the file has the correct properties
set (as the standard Unix ftp client does). It should only be readable
by user.
CURLOPTNETRCFILE
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 CURLOPTNETRC
is set, libcurl will attempt to find the a .netrc file in the
current user's home directory. (Added in 7.10.9)
CURLOPTUSERPWD
Pass a char * as parameter, which should be [user name]:[pass-
word] to use for the connection. Use CURLOPTHTPAUTH to decide
authentication method.
When using HTP and CURLOPTFOLOWLOCATION, 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 CURLOPTUNRESTRICTEDAUTH 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.
CURLOPTPROXYUSERPWD
Pass a char * as parameter, which should be [user name]:[pass-
word] to use for the connection to the HTP proxy. Use CUR-
LOPTPROXYAUTH to decide authentication method.
CURLOPTHTPAUTH
Pass a long as parameter, which is set to a bitmask, 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. Note that for some methods, this will induce an extra net-
work round-trip. Set the actual name and password with the CUR-
LOPTUSERPWD option. (Added in 7.10.6)
CURLAUTHBASIC
HTP Basic authentication. This is the default choice,
and the only method that is in wide-spread use and sup-
ported virtually everywhere. This is sending the user
name and password over the network in plain text, easily
captured by others.
CURLAUTHDIGEST
HTP 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.
CURLAUTHGSNEGOTIATE
HTP GS-Negotiate authentication. The GS-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 be also used along with another authentication
methods. For more information see IETF draft draft-
brezak-spnego-http-04.txt.
NOTE that you need to build libcurl with a suitable GS-
API library for this to work.
CURLAUTHNTLM
HTP 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.
NOTE that you need to build libcurl with SL support for
this option to work.
CURLAUTHANY
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.
CURLAUTHANYSAFE
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.
CURLOPTPROXYAUTH
Pass a long as parameter, which is set to a bitmask, 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. Note
that for some methods, this will induce an extra network round-
trip. Set the actual name and password with the CURLOPTPROX-
YUSERPWD option. The bitmask can be constructed by or'ing
together the bits listed above for the CURLOPTHTPAUTH option.
As of this writing, only Basic and NTLM work. (Added in 7.10.7)
HTP OPTIONS
CURLOPTAUTOREFERER
Pass a non-zero parameter to enable this. When enabled, libcurl
will automatically set the Referer: field in requests where it
follows a Location: redirect.
CURLOPTENCODING
Sets the contents of the Accept-Encoding: header sent in an HTP
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-NUL value) or else any
unsolicited encoding done by the server is ignored. See the spe-
cial file lib/README.encoding for details.
CURLOPTFOLOWLOCATION
A non-zero parameter tells the library to follow any Location:
header that the server sends as part of an HTP header.
NOTE:: this means that the library will re-send the same request
on the new location and follow new Location: headers all the way
until no more such headers are returned. CURLOPTMAXREDIRS can
be used to limit the number of redirects libcurl will follow.
CURLOPTUNRESTRICTEDAUTH
A non-zero parameter tells the library it can continue to send
authentication (user]password) when following locations, even
when hostname changed. Note that this is meaningful only when
setting CURLOPTFOLOWLOCATION.
CURLOPTMAXREDIRS
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 (CURLETOMANYREDIRECTS). This option only
makes sense if the CURLOPTFOLOWLOCATION is used at the same
time.
CURLOPTPUT
A non-zero parameter tells the library to use HTP PUT to trans-
fer data. The data should be set with CURLOPTREADATA and CUR-
LOPTINFILESIZE.
This option is deprecated and starting with version 7.12.1 you
should instead use CURLOPTUPLOAD.
CURLOPTPOST
A non-zero parameter tells the library to do a regular HTP
post. This will also make the library use the a "Content-Type:
application/x-www-form-urlencoded" header. (This is by far the
most commonly used POST method).
Use the CURLOPTPOSTFIELDS option to specify what data to post
and CURLOPTPOSTFIELDSIZE to set the data size.
Optionally, you can provide data to POST using the CURLOPTREAD-
FUNCTION and CURLOPTREADATA options but then you must make
sure to not set CURLOPTPOSTFIELDS to anything but NUL. 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 CURLOPTPOSTFIELDSIZE option.
You can override the default POST Content-Type: header by set-
ting your own with CURLOPTHTPHEADER.
Using POST with HTP 1.1 implies the use of a "Expect: 100-con-
tinue" header. You can disable this header with CURLOPTHTP-
HEADER as usual.
If you use POST to a HTP 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 CURLOPTHTPHEADER. With HTP 1.0 or
without chunked transfer, you must specify the size in the
request.
NOTE: if you have issued a POST request and want to make a HEAD
or GET instead, you must explictly pick the new request type
using CURLOPTNOBODY or CURLOPTHTPGET or similar.
CURLOPTPOSTFIELDS
Pass a char * as parameter, which should be the full data to
post in an HTP 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-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 CURLOPTPOST. Using CURLOPTPOSTFIELDS
implies CURLOPTPOST.
Using POST with HTP 1.1 implies the use of a "Expect: 100-con-
tinue" header. You can disable this header with CURLOPTHTP-
HEADER as usual.
Note:: to make multipart/formdata posts (aka rfc1867-posts),
check out the CURLOPTHTPOST option.
CURLOPTPOSTFIELDSIZE
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.
CURLOPTPOSTFIELDSIZELARGE
Pass a curlofft as parameter. Use this to set the size of the
CURLOPTPOSTFIELDS data to prevent libcurl from doing strlen()
on the data to figure out the size. This is the large file ver-
sion of the CURLOPTPOSTFIELDSIZE option. (Added in 7.11.1)
CURLOPTHTPOST
Tells libcurl you want a multipart/formdata HTP POST to be made
and you instruct what data to pass on to the server. Pass a
pointer to a linked list of curlhttppost structs as parameter.
. The easiest way to create such a list, is to use curlfor-
madd(3) as documented. The data in this list must remain intact
until you close this curl handle again with
curleasycleanup(3).
Using POST with HTP 1.1 implies the use of a "Expect: 100-con-
tinue" header. You can disable this header with CURLOPTHTP-
HEADER as usual.
CURLOPTREFERER
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 CURLOPTHTPHEADER.
CURLOPTUSERAGENT
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 CURLOPTHTP-
HEADER.
CURLOPTHTPHEADER
Pass a pointer to a linked list of HTP headers to pass to the
server in your HTP request. The linked list should be a fully
valid list of struct curlslist structs properly filled in. Use
curlslistappend(3) to create the list and
curlslistfreeall(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 contents as in 'Accept:' (no data on the right side of
the colon), the internally used header will get disabled. Thus,
using this option you can add new headers, replace internal
headers and remove internal headers. The headers included in the
linked list must not be CRLF-terminated, because curl adds CRLF
after each header item. Failure to comply with this will result
in strange bugs because the server will most likely ignore part
of the headers you specified.
The first line in a request (usually containing a GET or POST)
is not a header and cannot be replaced using this option. Only
the lines following the request-line are headers.
Pass a NUL to this to reset back to no custom headers.
NOTE:: The most commonly replaced headers have "shortcuts" in the
options CURLOPTCOKIE, CURLOPTUSERAGENT and CURLOPTREFERER.
CURLOPTHTP200ALIASES
Pass a pointer to a linked list of aliases to be treated as
valid HTP 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 HTP header line such as
"HTP/1.0 200 OK". (Added in 7.10.3)
The linked list should be a fully valid list of struct
curlslist structs, and be properly filled in. Use
curlslistappend(3) to create the list and
curlslistfreeall(3) to clean up an entire list.
NOTE:: The alias itself is not parsed for any version strings.
So if your alias is "MYHTP/9.9", Libcurl will not treat the
server as responding with HTP version 9.9. Instead Libcurl
will use the value set by option CURLOPTHTPVERSION.
CURLOPTCOKIE
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.
CURLOPTCOKIEFILE
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 HTP-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 request.
CURLOPTCOKIEJAR
Pass a file name as char *, zero terminated. This will make
libcurl write all internally known cookies to the specified file
when curleasycleanup(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.
NOTE:: If the cookie jar file can't be created or written to
(when the curleasycleanup(3) is called), libcurl will not and
cannot report an error for this. Using CURLOPTVERBOSE or CUR-
LOPTDEBUGFUNCTION will get a warning to display, but that is
the only visible feedback you get about this possibly lethal
situation.
CURLOPTCOKIESESION
Pass a long set to non-zero to mark this as a new cookie "ses-
sion". 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 are not. Session cookies are
cookies without expiry date and they are meant to be alive and
existing for this "session" only.
CURLOPTHTPGET
Pass a long. If the long is non-zero, this forces the HTP
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.
CURLOPTHTPVERSION
Pass a long, set to one of the values described below. They
force libcurl to use the specific HTP versions. This is not
sensible to do unless you have a good reason.
CURLHTPVERSIONONE
We don't care about what version the library uses.
libcurl will use whatever it thinks fit.
CURLHTPVERSION10
Enforce HTP 1.0 requests.
CURLHTPVERSION11
Enforce HTP 1.1 requests.
FTP OPTIONS
CURLOPTFTPORT
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, 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 NUL.
CURLOPTQUOTE
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 curlslistfreeall(3). Disable this operation again by
setting a NUL to this option.
CURLOPTPOSTQUOTE
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 curlslist structs properly
filled in as described for CURLOPTQUOTE. Disable this operation
again by setting a NUL to this option.
CURLOPTPREQUOTE
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 curlslist structs properly filled
in as described for CURLOPTQUOTE. Disable this operation again
by setting a NUL to this option.
CURLOPTFTPLISTONLY
A non-zero parameter tells the library to just list the names of
an ftp directory, instead of doing a full directory listing that
would include file sizes, dates etc.
This causes an FTP NLST command to be sent. Beware that some
FTP servers list only files in their response to NLST; they
might not include subdirectories and symbolic links.
CURLOPTFTPAPEND
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.
CURLOPTFTPUSEPRT
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 CURLOPTFTPORT). 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.
CURLOPTFTPUSEPSV
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.
CURLOPTFTPCREATEMISINGDIRS
Pass a long. If the value is non-zero, curl will attempt to cre-
ate any remote directory that it fails to CWD into. CWD is the
command that changes working directory. (Added in 7.10.7)
CURLOPTFTPRESPONSETIMEOUT
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. Note that while curl is waiting for
a response, this value overrides CURLOPTIMEOUT. It is recom-
mended that if used in conjunction with CURLOPTIMEOUT, you set
CURLOPTFTPRESPONSETIMEOUT to a value smaller than CUR-
LOPTIMEOUT. (Added in 7.10.8)
CURLOPTFTPSL
Pass a long using one of the values from below, to make libcurl
use your desired level of SL for the ftp transfer. (Added in
7.11.0)
CURLFTPSLNONE
Don't attempt to use SL.
CURLFTPSLTRY
Try using SL, proceed as normal otherwise.
CURLFTPSLCONTROL
Require SL for the control connection or fail with
CURLEFTPSLFAILED.
CURLFTPSLAL
Require SL for all communication or fail with
CURLEFTPSLFAILED.
CURLOPTFTPSLAUTH
Pass a long using one of the values from below, to alter how
libcurl issues "AUTH TLS" or "AUTH SL" when FTP over SL is
activated (see CURLOPTFTPSL). (Added in 7.12.2)
CURLFTPAUTHDEFAULT
Allow libcurl to decide
CURLFTPAUTHSL
Try "AUTH SL" first, and only if that fails try "AUTH
TLS"
CURLFTPAUTHTLS
Try "AUTH TLS" first, and only if that fails try "AUTH
SL"
CURLOPTSOURCEURL
When set, it enables a FTP third party transfer, using the set
URL as source, while CURLOPTURL is the target.
CURLOPTSOURCEUSERPWD
Set "username:password" to use for the source connection when
doing FTP third party transfers.
CURLOPTSOURCEQUOTE
Exactly like CURLOPTQUOTE, but for the source host.
CURLOPTSOURCEPREQUOTE
Exactly like CURLOPTPREQUOTE, but for the source host.
CURLOPTSOURCEPOSTQUOTE
Exactly like CURLOPTPOSTQUOTE, but for the source host.
CURLOPTFTPACOUNT
Pass a pointer to a zero-terminated string (or NUL 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 ACT
command. (Added in 7.13.0)
PROTOCOL OPTIONS
CURLOPTRANSFERTEXT
A non-zero parameter tells the library to use ASCI mode for ftp
transfers, instead of the default binary transfer. For LDAP
transfers it gets the data in plain text instead of HTML and for
win32 systems it does not set the stdout to binary mode. This
option can be usable when transferring text data between systems
with different views on certain characters, such as newlines or
similar.
CURLOPTCRLF
Convert Unix newlines to CRLF newlines on transfers.
CURLOPTRANGE
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. HTP transfers also support several intervals,
separated with commas as in "X-Y,N-M". Using this kind of multi-
ple intervals will cause the HTP server to send the response
document in pieces (using standard MIME separation techniques).
Pass a NUL to this option to disable the use of ranges.
CURLOPTRESUMEFROM
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).
CURLOPTRESUMEFROMLARGE
Pass a curlofft as parameter. It contains the offset in number
of bytes that you want the transfer to start from. (Added in
7.11.0)
CURLOPTCUSTOMREQUEST
Pass a pointer to a zero terminated string as parameter. It will
be user instead of GET or HEAD when doing an HTP 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
HTP requests. Don't do this at will, make sure your server sup-
ports the command first.
Restore to the internal default by setting this to NUL.
NOTE:: Many people have wrongly used this option to replace the
entire request with their own, including multiple headers and
POST contents. While that might work in many cases, it will
cause libcurl to send invalid requests and it could possibly
confuse the remote server badly. Use CURLOPTPOST and CUR-
LOPTPOSTFIELDS to set POST data. Use CURLOPTHTPHEADER to
replace or extend the set of headers sent by libcurl. Use CUR-
LOPTHTPVERSION to change HTP version.
CURLOPTFILETIME
Pass a long. If it is a non-zero value, libcurl will attempt to
get the modification date of the remote document in this opera-
tion. This requires that the remote server sends the time or
replies to a time querying command. The curleasygetinfo(3)
function with the CURLINFOFILETIME argument can be used after a
transfer to extract the received time (if any).
CURLOPTNOBODY
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 HTP(S) servers, this
will make libcurl do a HEAD request.
To change back to GET, you should use CURLOPTHTPGET. To change
back to POST, you should use CURLOPTPOST. Setting CUR-
LOPTNOBODY to zero has no effect.
CURLOPTINFILESIZE
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 CURLOPTINFILE-
SIZELARGE.
CURLOPTINFILESIZELARGE
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 curlofft. (Added in 7.11.0)
CURLOPTUPLOAD
A non-zero parameter tells the library to prepare for an upload.
The CURLOPTREADATA and CURLOPTINFILESIZE or CURLOPTINFILE-
SIZELARGE are also interesting for uploads. If the protocol is
HTP, uploading means using the PUT request unless you tell
libcurl otherwise.
Using PUT with HTP 1.1 implies the use of a "Expect: 100-con-
tinue" header. You can disable this header with CURLOPTHTP-
HEADER as usual.
If you use PUT to a HTP 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 CURLOPTHTPHEADER. With HTP 1.0 or
without chunked transfer, you must specify the size.
CURLOPTMAXFILESIZE
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
CURLEFILESIZEXCEDED will be returned.
NOTE:: The file size is not always known prior to download, and
for such files this option has no effect even if the file trans-
fer ends up being larger than this given limit. This concerns
both FTP and HTP transfers.
CURLOPTMAXFILESIZELARGE
Pass a curlofft 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 CURLEFILESIZEXCEDED will be returned. (Added in 7.11.0)
NOTE:: The file size is not always known prior to download, and
for such files this option has no effect even if the file trans-
fer ends up being larger than this given limit. This concerns
both FTP and HTP transfers.
CURLOPTIMECONDITION
Pass a long as parameter. This defines how the CURLOPTIMEVALUE
time value is treated. You can set this parameter to CURLTIME-
CONDIFMODSINCE or CURLTIMECONDIFUNMODSINCE. This feature
applies to HTP and FTP.
NOTE:: 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.
CURLOPTIMEVALUE
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 CURLOPTIMECONDITION.
CONECTION OPTIONS
CURLOPTIMEOUT
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.
NOTE:: this is not recommended to use in unix multi-threaded pro-
grams, as it uses signals unless CURLOPTNOSIGNAL (see above) is
set.
CURLOPTLOWSPEDLIMIT
Pass a long as parameter. It contains the transfer speed in
bytes per second that the transfer should be below during CUR-
LOPTLOWSPEDTIME seconds for the library to consider it too
slow and abort.
CURLOPTLOWSPEDTIME
Pass a long as parameter. It contains the time in seconds that
the transfer should be below the CURLOPTLOWSPEDLIMIT for the
library to consider it too slow and abort.
CURLOPTMAXCONECTS
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. 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 behav-
iour. This concerns connection using any of the protocols that
support persistent connections.
When reaching the maximum limit, curl uses the CURLOPTCLOSEPOL-
ICY to figure out which of the existing connections to close to
prevent the number of open connections to increase.
NOTE:: if you already have performed transfers with this curl
handle, setting a smaller MAXCONECTS than before may cause open
connections to get closed unnecessarily.
CURLOPTCLOSEPOLICY
Pass a long. This option sets what policy libcurl should use
when the connection cache is filled and one of the open connec-
tions has to be closed to make room for a new connection. This
must be one of the CURLCLOSEPOLICY* defines. Use CURLCLOSEPOL-
ICYLEASTRECENTLYUSED to make libcurl close the connection
that was least recently used, that connection is also least
likely to be capable of re-use. Use CURLCLOSEPOLICYOLDEST to
make libcurl close the oldest connection, the one that was cre-
ated first among the ones in the connection cache. The other
close policies are not support yet.
CURLOPTFRESHCONECT
Pass a long. Set to non-zero to make the next transfer use a new
(fresh) connection by force. If the connection cache is full
before this connection, one of the existing connections will be
closed as according to the selected or default policy. This
option should be used with caution and only if you understand
what it does. Set this to 0 to have libcurl attempt re-using an
existing connection (default behavior).
CURLOPTFORBIDREUSE
Pass a long. Set to non-zero to make the next transfer explic-
itly close the connection when done. Normally, libcurl keep all
connections alive when done with one transfer in case there
comes a succeeding one that can re-use them. This option should
be used with caution and only if you understand what it does.
Set to 0 to have libcurl keep the connection open for possibly
later re-use (default behavior).
CURLOPTCONECTIMEOUT
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 disable connection timeout (it
will then only timeout on the system's internal timeouts). See
also the CURLOPTIMEOUT option.
NOTE:: this is not recommended to use in unix multi-threaded pro-
grams, as it uses signals unless CURLOPTNOSIGNAL (see above) is
set.
CURLOPTIPRESOLVE
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:
CURLIPRESOLVEWHATEVER
Default, resolves addresses to all IP versions that your
system allows.
CURLIPRESOLVEV4
Resolve to ipv4 addresses.
CURLIPRESOLVEV6
Resolve to ipv6 addresses.
SL and SECURITY OPTIONS
CURLOPTSLCERT
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 CURLOPTSLCERTYPE.
CURLOPTSLCERTYPE
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)
CURLOPTSLCERTPASWD
Pass a pointer to a zero terminated string as parameter. It will
be used as the password required to use the CURLOPTSLCERT cer-
tificate.
This option is replaced by CURLOPTSLKEYPASWD 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 pri-
vate key.
CURLOPTSLKEY
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 CURLOPTSLKEYTYPE.
CURLOPTSLKEYTYPE
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".
NOTE:: The format "ENG" enables you to load the private key from
a crypto engine. In this case CURLOPTSLKEY is used as an iden-
tifier passed to the engine. You have to set the crypto engine
with CURLOPTSLENGINE. "DER" format key file currently does
not work because of a bug in OpenSL.
CURLOPTSLKEYPASWD
Pass a pointer to a zero terminated string as parameter. It will
be used as the password required to use the CURLOPTSLKEY pri-
vate key.
CURLOPTSLENGINE
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.
NOTE:: If the crypto device cannot be loaded,
CURLESLENGINENOTFOUND is returned.
CURLOPTSLENGINEDEFAULT
Sets the actual crypto engine as the default for (asymmetric)
crypto operations.
NOTE:: If the crypto device cannot be set, CURLESLENGINESET-
FAILED is returned.
CURLOPTSLVERSION
Pass a long as parameter. Set what version of SL to attempt to
use, 2 or 3. By default, the SL library will try to solve this
by itself although some servers make this difficult why you at
times may have to use this option.
CURLOPTSLVERIFYPER
Pass a long that is set to a zero value to stop curl from veri-
fying the peer's certificate (7.10 starting setting this option
to non-zero by default). Alternate certificates to verify
against can be specified with the CURLOPTCAINFO option or a
certificate directory can be specified with the CURLOPTCAPATH
option. As of 7.10, curl installs a default bundle. CUR-
LOPTSLVERIFYHOST may also need to be set to 1 or 0 if CUR-
LOPTSLVERIFYPER is disabled (it defaults to 2).
CURLOPTCAINFO
Pass a char * to a zero terminated string naming a file holding
one or more certificates to verify the peer with. This only
makes sense when used in combination with the CURLOPTSLVERI-
FYPER option.
CURLOPTCAPATH
Pass a char * to a zero terminated string naming a directory
holding multiple CA certificates to verify the peer with. The
certificate directory must be prepared using the openssl
crehash utility. This only makes sense when used in combination
with the CURLOPTSLVERIFYPER option. The CURLOPTCAPATH func-
tion apparently does not work in Windows due to some limitation
in openssl. (Added in 7.9.8)
CURLOPTRANDOMFILE
Pass a char * to a zero terminated file name. The file will be
used to read from to seed the random engine for SL. The more
random the specified file is, the more secure the SL connection
will become.
CURLOPTEGDSOCKET
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 SL.
CURLOPTSLVERIFYHOST
Pass a long. Set if we should verify the Common name from the
peer certificate in the SL handshake, set 1 to check existence,
2 to ensure that it matches the provided hostname. This is by
default set to 2. (default changed in 7.10)
CURLOPTSLCIPHERLIST
Pass a char *, pointing to a zero terminated string holding the
list of ciphers to use for the SL 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. Valid examples of cipher lists include 'RC4-SHA',
'SHA1]DES', 'TLSv1' and 'DEFAULT'. The default list is normally
set when you compile OpenSL.
You'll find more details about cipher lists on this URL:
http://www.openssl.org/docs/apps/ciphers.html
CURLOPTKRB4LEVEL
Pass a char * as parameter. Set the krb4 security level, this
also enables krb4 awareness. This is a string, 'clear', 'safe',
'confidential' or 'private'. If the string is set but doesn't
match one of these, 'private' will be used. Set the string to
NUL to disable kerberos4. The kerberos support only works for
FTP.
OTHER OPTIONS
CURLOPTPRIVATE
Pass a char * as parameter, pointing to data that should be
associated with this curl handle. The pointer can subsequently
be retrieved using curleasygetinfo(3) with the CURLINFOPRI-
VATE option. libcurl itself does nothing with this data. (Added
in 7.10.3)
CURLOPTSHARE
Pass a share handle as a parameter. The share handle must have
been created by a previous call to curlshareinit(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, you MUST use the locking methods in the
share handle. See curlsharesetopt(3) for details.
TELNET OPTIONS
CURLOPTELNETOPTIONS
Provide a pointer to a curlslist with variables to pass to the
telnet negotiations. The variables should be in the format
. libcurl supports the options 'TYPE', 'XDISPLOC'
and 'NEWENV'. See the TELNET standard for details.
RETURN VALUE
CURLEOK (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 CURLEFAILEDINIT.
SEE ALSO
curleasyinit(3), curleasycleanup(3), curleasyreset(3),
libcurl 7.13.0 25 Jan 2005 curleasysetopt(3)
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