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NAME
curl_easy_setopt - set options for a curl easy handle

SYNOPSIS
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLoption option, parameter);

DESCRIPTION
curl_easy_setopt() is used to tell libcurl how to behave. By using the appropriate options
to curl_easy_setopt, you can change libcurl's behavior. All options are set with the
option followed by a parameter. That parameter can be a long, a function pointer or an
object pointer, all depending on what the specific option expects. Read this manual care-
fully 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.

NOTE: strings passed to libcurl as 'char *' arguments, will not be copied by the library.
Instead you should keep them available until libcurl no longer needs them. Failing to do
so will cause very odd behavior or even crashes. libcurl will need them until you call
curl_easy_cleanup(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 infor-
mation about its operations. Very useful for libcurl and/or protocol debugging and
understanding. The verbose information will be sent to stderr, or the stream set
with CURLOPT_STDERR.

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 CUR-
LOPT_DEBUGFUNCTION.

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

CURLOPT_NOPROGRESS
A non-zero parameter tells the library to shut off the built-in progress meter com-
pletely.

NOTE: future versions of libcurl is likely to not have any built-in progress meter
at all.

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

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 termi-
nated. Return the number of bytes actually taken care of. If that amount differs
from the amount passed to your function, it'll signal an error to the library and
it will abort the transfer and return CURLE_WRITE_ERROR.

Set the stream argument with the CURLOPT_WRITEDATA option.

NOTE: you will be passed as much data as possible in all invokes, but you cannot
possibly make any assumptions. It may be one byte, it may be thousands. The maximum
amount of data that can be passed to the write callback is defined in the curl.h
header file: CURL_MAX_WRITE_SIZE.

CURLOPT_WRITEDATA
Data pointer to pass to the file write function. Note that if you specify the CUR-
LOPT_WRITEFUNCTION, this is the pointer you'll get as input. If you don't use a
callback, you must pass a 'FILE *' as libcurl will pass this to fwrite() when writ-
ing data.

NOTE: If you're using libcurl as a win32 DLL, you MUST use the CURLOPT_WRITEFUNC-
TION if you set this option or you will experience crashes.

This option is also known with the older name CURLOPT_FILE, the name CURLOPT_WRITE-
DATA was introduced in 7.9.7.

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

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 CURL_READFUNC_ABORT to
stop the current operation at once, with a CURLE_ABORTED_BY_CALLBACK error code
from the transfer.

CURLOPT_READDATA
Data pointer to pass to the file read function. Note that if you specify the CUR-
LOPT_READFUNCTION, this is the pointer you'll get as input. If you don't specify a
read callback, this must be a valid FILE *.

NOTE: If you're using libcurl as a win32 DLL, you MUST use a CURLOPT_READFUNCTION
if you set this option.

This option is also known with the older name CURLOPT_INFILE, the name CUR-
LOPT_READDATA was introduced in 7.9.7.

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

Also note that CURLOPT_NOPROGRESS must be set to FALSE to make this function actu-
ally get called.

CURLOPT_PROGRESSDATA
Pass a pointer that will be untouched by libcurl and passed as the first argument
in the progress callback set with 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 there is received header data that needs to be written down. The
headers are guaranteed to be written one-by-one and only complete lines are writ-
ten. Parsing headers should be easy enough using this. The size of the data pointed
to by ptr is size multiplied with nmemb. The pointer named stream will be the one
you passed to libcurl with the CURLOPT_WRITEHEADER option. Return the number of
bytes actually written or return -1 to signal error to the library (it will cause
it to abort the transfer with a CURLE_WRITE_ERROR return code).

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

CURLOPT_DEBUGFUNCTION
Function pointer that should match the following prototype: int curl_debug_callback
(CURL *, curl_infotype, char *, size_t, void *); CURLOPT_DEBUGFUNCTION replaces the
standard debug function used when CURLOPT_VERBOSE is in effect. This callback
receives debug information, as specified with the curl_infotype argument. This
function must return 0. The data pointed to by the char * passed to this function
WILL NOT be zero terminated, but will be exactly of the size as told by the size_t
argument.

Available curl_infotype values:

CURLINFO_TEXT
The data is informational text.

CURLINFO_HEADER_IN
The data is header (or header-like) data received from the peer.

CURLINFO_HEADER_OUT
The data is header (or header-like) data sent to the peer.

CURLINFO_DATA_IN
The data is protocol data received from the peer.

CURLINFO_DATA_OUT
The data is protocol data sent to the peer.

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

CURLOPT_SSL_CTX_FUNCTION
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 application to modify the behaviour of
openssl's ssl initialization. The sslctx parameter is actually a pointer to an
openssl SSL_CTX. If an error is returned no attempt to establish a connection is
made and the perform operation will return the error code from this callback func-
tion. Set the parm argument with the CURLOPT_SSL_CTX_DATA 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 call-
backs 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 set-
tings.

CURLOPT_SSL_CTX_DATA
Data pointer to pass to the ssl context callback set by the option CUR-
LOPT_SSL_CTX_FUNCTION, this is the pointer you'll get as third parameter, otherwise
NULL. (Added in 7.11.0)

ERROR OPTIONS
CURLOPT_ERRORBUFFER
Pass a char * to a buffer that the libcurl may store human readable error messages
in. This may be more helpful than just the return code from the library. The buffer
must be at least CURL_ERROR_SIZE big.

Use CURLOPT_VERBOSE and CURLOPT_DEBUGFUNCTION to better debug/trace why errors hap-
pen.

Note: if the library does not return an error, the buffer may not have been
touched. Do not rely on the contents in those cases.

CURLOPT_STDERR
Pass a FILE * as parameter. 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 300. The default action would be to return the page nor-
mally, ignoring that code.

NETWORK OPTIONS
CURLOPT_URL
The actual URL to deal with. The parameter should be a char * to a zero terminated
string. The string must remain present until curl no longer needs it, as it doesn't
copy the string.

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_UNSUPPORTED_PROTOCOL) when you call curl_easy_perform(3) or curl_multi_per-
form(3). Use curl_version_info(3) for detailed info on which protocols that are
supported.

NOTE: CURLOPT_URL is the only option that must be set before curl_easy_perform(3)
is called.

CURLOPT_PROTOCOLS can be used to limit what protocols libcurl will use for this
transfer, independent of what libcurl has been compiled to support. That may be
useful if you accept the URL from an external source and want to limit the accessi-
bility.

CURLOPT_PROTOCOLS
Pass a long that holds a bitmask of CURLPROTO_* defines. If used, this bitmask lim-
its what protocols libcurl may use in the transfer. This allows you to have a
libcurl built to support a wide range of protocols but still limit specific trans-
fers to only be allowed to use a subset of them. By default libcurl will accept all
protocols it supports. See also CURLOPT_REDIR_PROTOCOLS. (Added in 7.19.4)

CURLOPT_REDIR_PROTOCOLS
Pass a long that holds a bitmask of CURLPROTO_* defines. If used, this bitmask lim-
its what protocols libcurl may use in a transfer that it follows to in a redirect
when CURLOPT_FOLLOWLOCATION is enabled. This allows you to limit specific transfers
to only be allowed to use a subset of protocols in redirections. By default libcurl
will allow all protocols except for FILE. This is a difference compared to
pre-7.19.4 versions which unconditionally would follow to all protocols supported.
(Added in 7.19.4)

CURLOPT_PROXY
Set HTTP proxy to use. The parameter should be a char * to a zero terminated string
holding the host name or dotted IP address. To specify port number in this string,
append :[port] to the end of the host name. The proxy string may be prefixed with
[protocol]:// since any such prefix will be ignored. The proxy's port number may
optionally be specified with the separate option CURLOPT_PROXYPORT.

NOTE: 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
similar FTP specifics that don't work unless you tunnel through the HTTP proxy.
Such tunneling is activated with CURLOPT_HTTPPROXYTUNNEL.

NOTE2: libcurl respects the environment variables http_proxy, ftp_proxy, all_proxy
etc, if any of those is set.

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

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

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

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_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 variable.

WARNING: this option is considered obsolete. Stop using it. Switch over to using
the share interface instead! See CURLOPT_SHARE and curl_share_init(3).

CURLOPT_BUFFERSIZE
Pass a long specifying your preferred size 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)

CURLOPT_PORT
Pass a long specifying what remote port number to connect to, instead of the one
specified in the URL or the default port for the used protocol.

CURLOPT_TCP_NODELAY
Pass a long specifying whether the TCP_NODELAY option should be set or cleared (1 =
set, 0 = clear). The option is cleared by default. This will have no effect after
the connection has been established.

Setting this option will disable TCP's Nagle algorithm. The purpose of this algo-
rithm is to try to minimize the number of small packets on the network (where
"small packets" means TCP segments less than the Maximum Segment Size (MSS) for the
network).

Maximizing the amount of data sent per TCP segment is good because it amortizes the
overhead of the send. However, in some cases (most notably telnet or rlogin) small
segments may need to be sent without delay. This is less efficient than sending
larger amounts of data at a time, and can contribute to congestion on the network
if overdone.

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.

Note: libcurl uses a user name (and supplied or prompted password) supplied with
CURLOPT_USERPWD in preference to any of the options controlled by this parameter.

Pass a long, set to one of the values described below.

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

Undefined values of the option will have this effect.

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

This is the default.

CURL_NETRC_REQUIRED
This value tells the library that use of the file is required, to ignore the
information in the URL, and to search the file with the host only.
Only machine name, user name and password are taken into account (init macros and similar
things aren't supported).

Note: libcurl does not verify that the file has the correct properties set (as the stan-
dard Unix ftp client does). It should only be readable by user.

CURLOPT_NETRC_FILE
Pass a char * as parameter, pointing to a zero terminated string containing the
full path name to the file you want libcurl to use as .netrc file. If this option
is omitted, and CURLOPT_NETRC is set, libcurl will attempt to find 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 HTTP and CURLOPT_FOLLOWLOCATION, libcurl might perform several requests
to possibly different hosts. libcurl will only send this user and password informa-
tion 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 bitmask, to tell libcurl what authenti-
cation 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 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 send-
ing the user name and password over the network in plain text, easily cap-
tured by others.

CURLAUTH_DIGEST
HTTP Digest authentication. Digest authentication is defined in RFC2617 and
is a more secure way to do authentication over public networks than the reg-
ular 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.

NOTE that you need to build libcurl with a suitable GSS-API library for this
to work.

CURLAUTH_NTLM
HTTP NTLM authentication. A proprietary protocol invented and used by
Microsoft. It uses a challenge-response and hash concept similar to Digest,
to prevent the password from being eavesdropped.

NOTE that you need to build libcurl with SSL support for this option to
work.

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 bitmask, to tell libcurl what authenti-
cation 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 meth-
ods 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 CURLOPT_PROXYUSERPWD option. The bitmask can be constructed by
or'ing together the bits listed above for the CURLOPT_HTTPAUTH option. As of this
writing, only Basic 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 Referer: field in requests where it follows a Location: 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 algorithm. If a zero-length string is set, then an Accept-Encoding:
header containing all supported encodings is sent.

This is a request, not an order; the server may or may not do it. This option must
be set (to any non-NULL value) or else any unsolicited encoding done by the server
is ignored. See the special file lib/README.encoding for details.

CURLOPT_FOLLOWLOCATION
A non-zero parameter tells the library to follow any Location: header that the
server sends as part of an HTTP header.

NOTE: this means that the library will re-send the same request on the new location
and follow new Location: headers all the way until no more such headers are
returned. CURLOPT_MAXREDIRS can be used to limit the number of redirects libcurl
will follow.

CURLOPT_UNRESTRICTED_AUTH
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 CURLOPT_FOLLOWLOCATION.

CURLOPT_MAXREDIRS
Pass a long. The set number will be the redirection limit. If that many redirec-
tions have been followed, the next redirect will cause an error
(CURLE_TOO_MANY_REDIRECTS). This option only makes sense if the CURLOPT_FOLLOWLOCA-
TION is used at the same time.

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.

NOTE: since 7.19.4, libcurl can limit to what protocols it will automatically fol-
low. The accepted protocols are set with CURLOPT_REDIR_PROTOCOLS and it excludes
the FILE protocol by default.

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 regular HTTP post. This is a normal
application/x-www-form-urlencoded kind, which is the most commonly used one by HTML
forms. See the CURLOPT_POSTFIELDS option for how to specify the data to post and
CURLOPT_POSTFIELDSIZE in how to set the data size. Using the CURLOPT_POSTFIELDS
option implies this option.

CURLOPT_POSTFIELDS
Pass a char * as parameter, which should be the full data to post in an HTTP post
operation. You need to 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 CURLOPT_POST. Using CURLOPT_POSTFIELDS implies
CURLOPT_POST.

Note: to make multipart/formdata posts (aka rfc1867-posts), check out the CUR-
LOPT_HTTPPOST option.

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

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 HTTP post
structs as parameter. The linked list should be a fully valid list of 'struct
HttpPost' structs properly filled in. The best and most elegant way to do this, is
to use curl_formadd(3) as documented. The data in this list must remain intact
until you close this curl handle again with curl_easy_cleanup(3).

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

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

CURLOPT_HTTPHEADER
Pass a pointer to a linked list of HTTP headers to pass to the server in your HTTP
request. The linked list should be a fully valid list of struct curl_slist structs
properly filled in. Use curl_slist_append(3) to create the list and
curl_slist_free_all(3) to clean up an entire list. If you add a header that is
otherwise generated and used by libcurl internally, your added one will be used
instead. If you add a header with no contents as in 'Accept:' (no data on the right
side of the colon), the internally used header will get disabled. Thus, using this
option you can add new headers, replace internal headers and remove internal head-
ers. 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 NULL to this to reset back to no custom headers.

NOTE: The most commonly replaced headers have "shortcuts" in the options CUR-
LOPT_COOKIE, CURLOPT_USERAGENT and CURLOPT_REFERER.

CURLOPT_HTTP200ALIASES
Pass a pointer to a linked list of aliases to be treated as valid HTTP 200
responses. Some servers respond with a custom header response line. For example,
IceCast servers respond with "ICY 200 OK". By including this string in your list
of aliases, the response will be treated as a valid HTTP header line such as
"HTTP/1.0 200 OK". (Added in 7.10.3)

The linked list should be a fully valid list of struct curl_slist structs, and be
properly filled in. Use curl_slist_append(3) to create the list and
curl_slist_free_all(3) to clean up an entire list.

NOTE: The alias itself is not parsed for any version strings. So if your alias is
"MYHTTP/9.9", Libcurl will not treat the server as responding with HTTP version
9.9. Instead Libcurl will use the value set by option CURLOPT_HTTP_VERSION.

CURLOPT_COOKIE
Pass a pointer to a zero terminated string as parameter. It will be used to set a
cookie in the http request. The format of the string should be NAME=CONTENTS, where
NAME is the cookie name and CONTENTS is what the cookie should contain.

If you need to set 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 cook-
ies in one string like this: "name1=content1; name2=content2;" etc.

Using this option multiple times will only make the latest string override the pre-
viously ones.

CURLOPT_COOKIEFILE
Pass a pointer to a zero terminated string as parameter. It should contain the name
of your file holding cookie data to read. The cookie data may be in Netscape /
Mozilla cookie data format or just regular HTTP-style headers dumped to a file.

Given an empty or non-existing file, this option will enable cookies for this curl
handle, making it understand and parse received cookies and then use matching cook-
ies in future request.

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

NOTE: 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_DEBUGFUNCTION will get a warning to display,
but that is the only visible feedback you get about this possibly lethal situation.

CURLOPT_COOKIESESSION
Pass a long set to 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,
independent 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.

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

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 rea-
son.

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

CURL_HTTP_VERSION_1_0
Enforce HTTP 1.0 requests.

CURL_HTTP_VERSION_1_1
Enforce HTTP 1.1 requests.

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

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.

CURLOPT_FTPLISTONLY
A non-zero parameter tells the library to just list the names of an ftp directory,
instead of doing a full directory listing that would include file sizes, dates etc.

This causes an FTP NLST command to be sent. Beware that some FTP servers list only
files in their response to NLST; they might not include subdirectories and symbolic
links.

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

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.

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 direc-
tory. (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 considered hung. Note that while curl is waiting
for a response, this value overrides CURLOPT_TIMEOUT. It is recommended that if
used in conjunction with CURLOPT_TIMEOUT, you set CURLOPT_FTP_RESPONSE_TIMEOUT to a
value smaller than CURLOPT_TIMEOUT. (Added in 7.10.8)

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.

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

CURLOPT_CRLF
Convert Unix newlines to CRLF newlines on transfers.

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

CURLOPT_RESUME_FROM_LARGE
Pass an curl_off_t as parameter. It contains the offset in number of bytes that you
want the transfer to start from. (Added in 7.11.0)

CURLOPT_CUSTOMREQUEST
Pass a pointer to a zero terminated string as parameter. It 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.

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 CURLOPT_POST and CURLOPT_POSTFIELDS to set
POST data. Use CURLOPT_HTTPHEADER to replace or extend the set of headers sent by
libcurl. Use CURLOPT_HTTP_VERSION to change HTTP version.

CURLOPT_FILETIME
Pass a long. If it is a non-zero value, libcurl will attempt to get the modifica-
tion 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_get-
info(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.

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.

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)

CURLOPT_UPLOAD
A non-zero parameter tells the library to prepare for an upload. The CURLOPT_READ-
DATA and CURLOPT_INFILESIZE_LARGE are also interesting for uploads. If the protocol
is HTTP, uploading means using the PUT request unless you tell libcurl otherwise.

CURLOPT_MAXFILESIZE
Pass a long as parameter. This allows you to specify the maximum size (in bytes) of
a file to download. If the file requested is larger than this value, the transfer
will not start and CURLE_FILESIZE_EXCEEDED will be returned.

NOTE: The file size is not always known prior to download, and for such files this
option has no effect even if the file transfer ends up being larger than this given
limit. This concerns both FTP and HTTP transfers.

CURLOPT_MAXFILESIZE_LARGE
Pass a curl_off_t as parameter. This allows you to specify the maximum size (in
bytes) of a file to download. If the file requested is larger than this value, the
transfer will not start and CURLE_FILESIZE_EXCEEDED will be returned. (Added in
7.11.0)

CURLOPT_TIMECONDITION
Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE time value is
treated. You can set this parameter to CURL_TIMECOND_IFMODSINCE or CURL_TIME-
COND_IFUNMODSINCE. This feature applies to HTTP 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.

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

CONNECTION OPTIONS
CURLOPT_TIMEOUT
Pass a long as parameter containing the maximum time in seconds that you allow the
libcurl transfer operation to take. Normally, name lookups can take a considerable
time and limiting operations to less than a few minutes risk aborting perfectly
normal operations. This option will cause curl to use the SIGALRM to enable time-
outing system calls.

NOTE: this is not recommended to use in unix multi-threaded programs, as it uses
signals unless CURLOPT_NOSIGNAL (see above) is set.

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

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

CURLOPT_MAXCONNECTS
Pass a long. The set number will be the persistent connection cache size. The set
amount will be the maximum amount of simultaneously open connections that libcurl
may cache. Default is 5, and there isn't much point in changing this value unless
you are perfectly aware of how this work and changes libcurl's behaviour. This con-
cerns connection using any of the protocols that support persistent connections.

When reaching the maximum limit, curl uses the CURLOPT_CLOSEPOLICY to figure out
which of the existing connections to close to prevent the number of open connec-
tions to increase.

NOTE: if you already have performed transfers with this curl handle, setting a
smaller MAXCONNECTS than before may cause open connections to get closed unneces-
sarily.

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

CURLOPT_FRESH_CONNECT
Pass a long. Set to non-zero to make the next transfer use a new (fresh) connection
by force. If the connection cache is full before this connection, one of the exist-
ing 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 behav-
ior).

CURLOPT_FORBID_REUSE
Pass a long. Set to non-zero to make the next transfer explicitly close the connec-
tion 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).

CURLOPT_CONNECTTIMEOUT
Pass a long. It should contain the maximum time in seconds that you allow the con-
nection 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 CUR-
LOPT_TIMEOUT option.

NOTE: this is not recommended to use in unix multi-threaded programs, as it uses
signals unless CURLOPT_NOSIGNAL (see above) is set.

CURLOPT_IPRESOLVE
Allows an application to select what kind of IP addresses to use when resolving
host names. This is only interesting when using host names that resolve addresses
using more than one version of IP. The allowed values are:

CURL_IPRESOLVE_WHATEVER
Default, resolves addresses to all IP versions that your system allows.

CURL_IPRESOLVE_V4
Resolve to ipv4 addresses.

CURL_IPRESOLVE_V6
Resolve to ipv6 addresses.

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

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

CURLOPT_SSLCERTPASSWD
Pass a pointer to a zero terminated string as parameter. It will be used as the
password required to use the CURLOPT_SSLCERT certificate.

This option is replaced by CURLOPT_SSLKEYPASSWD and should only be used for back-
ward 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".

NOTE: The format "ENG" enables you to load the private key from a crypto engine. In
this case CURLOPT_SSLKEY is used as an identifier passed to the engine. You have to
set the crypto engine with CURLOPT_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 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.

NOTE: 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.

NOTE: If the crypto device cannot be set, CURLE_SSL_ENGINE_SETFAILED is returned.

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

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

CURLOPT_CAINFO
Pass a char * to a zero terminated string naming a file holding one or more cer-
tificates to verify the peer with. This only makes sense when used in combination
with the CURLOPT_SSL_VERIFYPEER option.

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

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

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

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

CURLOPT_SSL_CIPHER_LIST
Pass a char *, pointing to a zero terminated string holding the list of ciphers to
use for the SSL connection. The list must be syntactically correct, it consists of
one or more cipher strings separated by colons. Commas or spaces are also accept-
able separators but colons are normally used, , - and + can be used as operators.
Valid examples of cipher lists include 'RC4-SHA', ?SHA1+DES?, 'TLSv1' and
'DEFAULT'. The default list is normally set when you compile OpenSSL.

You'll find more details about cipher lists on this URL:
http://www.openssl.org/docs/apps/ciphers.html

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

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 handle must have been created by a
previous call to curl_share_init(3). Setting this option, will make this curl han-
dle 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 simultane-
ously, 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 negotia-
tions. The variables should be in the format <option=value>. libcurl supports the
options 'TTYPE', 'XDISPLOC' and 'NEW_ENV'. See the TELNET standard for details.

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

If you try to set an option that libcurl doesn't know about, perhaps because the library
is too old to support it or the option was removed in a recent version, this function will
return CURLE_FAILED_INIT.

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

libcurl 7.11.1 12 Mar 2004 curl_easy_setopt(3)

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