curl/docs/curl_easy_setopt.3

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.\" Written by daniel@haxx.se
.\"
.TH curl_easy_setopt 3 "10 April 2001" "libcurl 7.7.2" "libcurl Manual"
.SH NAME
curl_easy_setopt - Set curl easy-session options
.SH SYNOPSIS
.B #include <curl/curl.h>
.sp
.BI "CURLcode curl_easy_setopt(CURL *" handle ", CURLoption "option ", ...);"
.ad
.SH DESCRIPTION
curl_easy_setopt() is called to tell libcurl how to behave in a number of
ways. Most operations in libcurl have default actions, and by using the
appropriate options you can make them behave differently (as documented).  All
options are set with the
.I option
followed by a parameter. That parameter can be a long, a function pointer or
an object pointer, all depending on what the option in question expects. Read
this manual carefully as bad input values may cause libcurl to behave badly!
You can only set one option in each function call. A typical application uses
many curl_easy_setopt() calls in the setup phase.

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 behaviour or even crashes.

More note: the options set with this function call are valid for the
forthcoming data transfers that are performed when you invoke
.I curl_easy_perform .
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.

The
.I "handle"
is the return code from the
.I "curl_easy_init"
call.
.SH OPTIONS
These options are in a bit of random order, but you'll figure it out!
.TP 0.8i
.B CURLOPT_FILE
Data pointer to pass to file write function. Note that if you specify the
.I CURLOPT_WRITEFUNCTION
, this is the pointer you'll get as input. If you don't use a callback, you
must pass a 'FILE *' as libcurl passes it to fwrite() when writing data.

NOTE: If you're using libcurl as a win32 DLL, you MUST use the
\fICURLOPT_WRITEFUNCTION\fP if you set this option.
.TP
.B CURLOPT_WRITEFUNCTION
Function pointer that should match the following prototype:
.BI "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 data that
needs to be written down. The size of the data pointed to by \fIptr\fP is
\fIsize\fP multiplied with \fInmemb\fP.  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 CURLE_WRITE_ERROR).

Set the \fIstream\fP argument with the \fBCURLOPT_FILE\fP option.
.TP
.B CURLOPT_INFILE
Data pointer to pass to the file read function. Note that if you specify the
\fICURLOPT_READFUNCTION\fP, 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
\fICURLOPT_READFUNCTION\fP if you set this option.
.TP
.B CURLOPT_READFUNCTION
Function pointer that should match the following prototype:
.BI "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 \fIptr\fP may
be filled with at most \fIsize\fP multiplied with \fInmemb\fP number of
bytes. Your function must return the actual number of bytes that you stored in
that memory area. Returning -1 will signal an error to the library and cause
it to abort the current transfer immediately (with a CURLE_READ_ERROR return
code).
.TP
.B 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.
.TP
.B 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. NOTE: this option is required to be set
before curl_easy_perform() is called.
.TP
.B CURLOPT_PROXY
If you need libcurl to use a http proxy to access the outside world, set the
proxy string with this option. The parameter should be a char * to a zero
terminated string. 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.
.TP
.B CURLOPT_PROXYPORT
Set this long with this option to set the proxy port to use unless it is
specified in the proxy string CURLOPT_PROXY.
.TP
.B CURLOPT_HTTPPROXYTUNNEL
Set the parameter to non-zero to get the library to tunnel all non-HTTP
operations through the given HTTP proxy. Do note that there is a big
difference to use a proxy and to tunnel through it. If you don't know what
this means, you probably don't want this tunnel option. (Added in libcurl 7.3)
.TP
.B CURLOPT_VERBOSE
Set the parameter to non-zero to get the library to display a lot of verbose
information about its operations.
.TP
.B CURLOPT_HEADER
A non-zero parameter tells the library to include the header in the
output. This is only relevant for protocols that actually has a header
preceeding the data (like HTTP).
.TP
.B CURLOPT_NOPROGRESS
A non-zero parameter tells the library to shut of the built-in progress meter
completely. (NOTE: future versions of the lib is likely to not have any
built-in progress meter at all).
.TP
.B 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 a separate header and
body part.
.TP
.B CURLOPT_FAILONERROR
A non-zero parameter tells the library to fail silently if the HTTP code
returned is equal or larger than 300. The default action would be to return
the page normally, ignoring that code.
.TP
.B CURLOPT_UPLOAD
A non-zero parameter tells the library to prepare for an upload. The
CURLOPT_INFILE and CURLOPT_INFILESIZE are also interesting for uploads.
.TP
.B 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.
.TP
.B CURLOPT_FTPLISTONLY
A non-zero parameter tells the library to just list the names of an ftp
directory, instead of doing a full directory listin that would include file
sizes, dates etc.
.TP
.B 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 a ftp site.
.TP
.B CURLOPT_NETRC
A non-zero parameter tells the library to scan your
.I ~/.netrc
file to find user name and password for the remote site you are about to
access. Do note that curl does not verify that the file has the correct
properties set (as the standard unix ftp client does), and that only machine
name, user name and password is taken into account (init macros and similar
things aren't supported).
.TP
.B CURLOPT_FOLLOWLOCATION
A non-zero parameter tells the library to follow any Location: header that the
server sends as part of a HTTP header. NOTE that this means that the library
will resend the same request on the new location and follow new Location:
headers all the way until no more such headers are returned.
.TP
.B 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 useable when transfering text data between
system with different views on certain characters, such as newlines or
similar.
.TP
.B CURLOPT_PUT
A non-zero parameter tells the library to use HTTP PUT a file. The file to put
must be set with CURLOPT_INFILE and CURLOPT_INFILESIZE.
.TP
.B CURLOPT_MUTE
A non-zero parameter tells the library to be completely quiet.
.TP
.B CURLOPT_USERPWD
Pass a char * as parameter, which should be [username]:[password] to use for
the connection. If the password is left out, you will be prompted for it.
.TP
.B CURLOPT_PROXYUSERPWD
Pass a char * as parameter, which should be [username]:[password] to use for
the connection to the HTTP proxy. If the password is left out, you will be
prompted for it.
.TP
.B 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
.I "X-Y,N-M"
. Using this kind of multiple intervals will cause the HTTP server to send the
response document in pieces.
.TP
.B 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.
.TP
.B CURLOPT_TIMEOUT
Pass a long as parameter containing the maximum time in seconds that you allow
the libcurl transfer operation to take. Do note that normally, name lookups
maky take a considerable time and that limiting the operation to less than a
few minutes risk aborting perfectly normal operations. This option will cause
curl to use the SIGALRM to enable timeouting system calls.
.TP
.B CURLOPT_POSTFIELDS
Pass a char * as parameter, which should be the full data to post in a HTTP
post operation. See also the CURLOPT_POST.
.TP
.B 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. Also, 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 data
size. (Added in libcurl 7.2)
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B 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.
.TP
.B CURLOPT_RESUME_FROM
Pass a long as parameter. It contains the offset in number of bytes that you
want the transfer to start from.
.TP
.B 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.
.TP
.B 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
.I curl_slist_append(3)
to create the list and
.I 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:', the internally used header will
just get disabled. Thus, using this option you can add new headers, replace
internal headers and remove internal headers.
.TP
.B 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
.I curl_formparse(3)
as documented.
.TP
.B CURLOPT_SSLCERT
Pass a pointer to a zero terminated string as parameter. The string should be
the file name of your certficicate in PEM format.
.TP
.B 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. If the password
is not supplied, you will be prompted for it.
.TP
.B CURLOPT_CRLF
Convert unix newlines to CRLF newlines on FTP uploads.
.TP
.B CURLOPT_QUOTE
Pass a pointer to a linked list of FTP commands to pass to the server prior to
your ftp request. The linked list should be a fully valid list of 'struct
curl_slist' structs properly filled in. Use
.I curl_slist_append(3)
to append strings (commands) to the list, and clear the entire list afterwards
with
.I curl_slist_free_all(3)
.TP
.B 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
.I "CURLOPT_QUOTE"
.TP
.B CURLOPT_WRITEHEADER
Pass a pointer to be used to write the header part of the received data to. If
you don't use a callback to take care of the writing, this must be a FILE
*. The headers are guaranteed to be written one-by-one and only complete lines
are written. Parsing headers should be easy enough using this. See also the
\fICURLOPT_HEADERFUNCTION\fP option.
.TP
.B CURLOPT_HEADERFUNCTION
Function pointer that should match the following prototype:
.BI "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 function will be called once for each
header with a complete header line in each invoke. The size of the data
pointed to by
.I ptr 
is
.I size
multiplied with
.I nmemb.
The pointer named
.I stream
will be the one you passed to libcurl with the
.I 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
.I CURLE_WRITE_ERROR
return code). (Added in libcurl 7.7.2)
.TP
.B CURLOPT_COOKIEFILE
Pass a pointer to a zero terminated string as parameter. It should contain the
name of your file holding cookie data. The cookie data may be in netscape
cookie data format or just regular HTTP-style headers dumped to a file.
.TP
.B 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 will have to use this option.
.TP
.B CURLOPT_TIMECONDITION
Pass a long as parameter. This defines how the CURLOPT_TIMEVALUE time value is
treated. You can set this parameter to TIMECOND_IFMODSINCE or
TIMECOND_IFUNMODSINCE. This is aa HTTP-only feature. (TBD)
.TP
.B CURLOPT_TIMEVALUE
Pass a long as parameter. This should be the time in seconds since 1 jan 1970,
and the time will be used as specified in CURLOPT_TIMECONDITION or if that
isn't used, it will be TIMECOND_IFMODSINCE by default.
.TP
.B CURLOPT_CUSTOMREQUEST
Pass a pointer to a zero terminated string as parameter. It will be user
instead of GET or HEAD when doing the HTTP request. This is useful for doing
DELETE or other more obscure HTTP requests. Don't do this at will, make sure
your server supports the command first.
.TP
.B CURLOPT_STDERR
Pass a FILE * as parameter. This is the stream to use instead of stderr
internally when reporting errors.
.TP
.B 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. (Added in libcurl 7.3)
.TP
.B 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. (Added in libcurl 7.3)
.TP
.B CURLOPT_WRITEINFO
(NOT PRESENT IN 7.4 or later!)
Pass a pointer to a zero terminated string as parameter. It will be used to
report information after a successful request. This string may contain
variables that will be substituted by their contents when output. Described
elsewhere.
.TP
.B CURLOPT_PROGRESSFUNCTION
Function pointer that should match the
.BI curl_progress_callback
prototype found in
.I <curl/curl.h>
This function gets called by libcurl instead of its internal
equivalent. 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.
.TP
.B CURLOPT_PROGRESSDATA
Pass a pointer that will be untouched by libcurl and passed as the first
argument in the progress callback set with
.I CURLOPT_PROGRESSFUNCTION
 .
.TP
.B CURLOPT_SSL_VERIFYPEER
Pass a long that is set to a non-zero value to make curl verify the peer's
certificate. The certificate to verify against must be specified with the
CURLOPT_CAINFO option. (Added in 7.4.2)
.TP
.B CURLOPT_CAINFO
Pass a char * to a zero terminated file naming holding the certificate to
verify the peer with. This only makes sense when used in combination with the
CURLOPT_SSL_VERIFYPEER option. (Added in 7.4.2)
.TP
.B CURLOPT_PASSWDFUNCTION
Pass a pointer to a curl_passwd_callback function that will then be called
instead of the internal one if libcurl requests a password. The function must
match this prototype:
.BI "int my_getpass(void *client, char *prompt, char* buffer, int buflen );"
If set to NULL, it equals to making the function always fail. If the function
returns a non-zero value, it will abort the operation and an error
(CURLE_BAD_PASSWORD_ENTERED) will be returned.
.I client
is a generic pointer, see CURLOPT_PASSWDDATA.
.I prompt
is a zero-terminated string that is text that prefixes the input request.
.I buffer
is a pointer to data where the entered password should be stored and
.I buflen
is the maximum number of bytes that may be written in the buffer.
(Added in 7.4.2)
.TP
.B CURLOPT_PASSWDDATA
Pass a void * to whatever data you want. The passed pointer will be the first
argument sent to the specifed CURLOPT_PASSWDFUNCTION function. (Added in
7.4.2)
.TP
.B CURLOPT_FILETIME
Pass a long. If it is a non-zero value, libcurl will attempt to get the
modification date of the remote document in this operation. This requires that
the remote server sends the time or replies to a time querying command. The
curl_easy_getinfo() function with the CURLINFO_FILETIME argument can be used
after a transfer to extract the received time (if any). (Added in 7.5)
.TP
.B CURLOPT_MAXREDIRS
Pass a long. The set number will be the redirection limit. If that many
redirections have been followed, the next redirect will cause an error. This
option only makes sense if the CURLOPT_FOLLOWLOCATION is used at the same
time. (Added in 7.5)
.TP
.B CURLOPT_MAXCONNECTS
Pass a long. The set number will be the persistant connection cache size. The
set amount will be the maximum amount of simultaneous connections that libcurl
may cache between file transfers. 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. Note: if you have already performed transfers
with this curl handle, setting a smaller MAXCONNECTS than before may cause
open connections to unnecessarily get closed. (Added in 7.7)
.TP
.B 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 CURLCLOSEPOLICY_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. (Added in 7.7)
.TP
.B CURLOPT_FRESH_CONNECT
Pass a long. Set to non-zero to make the next transfer use a new connection by
force. If the connection cache is full before this connection, one of the
existinf connections will be closed as according to the set policy. This
option should be used with caution and only if you understand what it
does. Set to 0 to have libcurl attempt re-use of an existing connection.
(Added in 7.7)
.TP
.B CURLOPT_FORBID_REUSE
Pass a long. Set to non-zero to make the next transfer explicitly close the
connection when done. Normally, libcurl keep all connections alive when done
with one transfer in case there comes a 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. (Added in 7.7)
.TP
.B 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 will the SSL connection become.
.TP
.B 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.
.TP
.B CURLOPT_CONNECTTIMEOUT
Pass a long. It should contain the maximum time in seconds that you allow the
connection to the server to take.  This only limits the connection phase, once
it has connected, this option is of no more use. Set to zero to disable
connection timeout (it will then only timeout on the system's internal
timeouts). This option doesn't work in win32 systems.  See also the
.I CURLOPT_TIMEOUT
option.
.PP
.SH RETURN VALUE
0 means the option was set properly, non-zero means an error as
.I <curl/curl.h>
defines
.SH "SEE ALSO"
.BR curl_easy_init "(3), " curl_easy_cleanup "(3), "
.SH BUGS
Surely there are some, you tell me!