repo/core/curl/files/CURLOPT_POST.3

.\" generated by cd2nroff 0.1 from CURLOPT_POST.md
.TH CURLOPT_POST 3 "2024-08-02" libcurl
.SH NAME
CURLOPT_POST \- make an HTTP POST
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POST, long post);
.fi
.SH DESCRIPTION
A parameter set to 1 tells libcurl to do a regular HTTP post. This also makes
libcurl use a "Content\-Type: application/x\-www\-form\-urlencoded" header. This
is the most commonly used POST method.

Use one of \fICURLOPT_POSTFIELDS(3)\fP or \fICURLOPT_COPYPOSTFIELDS(3)\fP
options to specify what data to post and \fICURLOPT_POSTFIELDSIZE(3)\fP or
\fICURLOPT_POSTFIELDSIZE_LARGE(3)\fP to set the data size.

Optionally, you can provide data to POST using the
\fICURLOPT_READFUNCTION(3)\fP and \fICURLOPT_READDATA(3)\fP options but then
you must make sure to not set \fICURLOPT_POSTFIELDS(3)\fP to anything but
NULL. When providing data with a callback, you must transmit it using chunked
transfer\-encoding or you must set the size of the data with the
\fICURLOPT_POSTFIELDSIZE(3)\fP or \fICURLOPT_POSTFIELDSIZE_LARGE(3)\fP
options. To enable chunked encoding, you simply pass in the appropriate
Transfer\-Encoding header, see the post\-callback.c example.

You can override the default POST Content\-Type: header by setting your own
with \fICURLOPT_HTTPHEADER(3)\fP.

Using POST with HTTP 1.1 implies the use of a "Expect: 100\-continue" header.
You can disable this header with \fICURLOPT_HTTPHEADER(3)\fP as usual.

If you use POST to an HTTP 1.1 server, you can send data without knowing the
size before starting the POST if you use chunked encoding. You enable this by
adding a header like "Transfer\-Encoding: chunked" with
\fICURLOPT_HTTPHEADER(3)\fP. With HTTP 1.0 or without chunked transfer, you
must specify the size in the request. (Since 7.66.0, libcurl automatically
uses chunked encoding for POSTs if the size is unknown.)

When setting \fICURLOPT_POST(3)\fP to 1, libcurl automatically sets
\fICURLOPT_NOBODY(3)\fP and \fICURLOPT_HTTPGET(3)\fP to 0.

If you issue a POST request and then want to make a HEAD or GET using the same
reused handle, you must explicitly set the new request type using
\fICURLOPT_NOBODY(3)\fP or \fICURLOPT_HTTPGET(3)\fP or similar.

When setting \fICURLOPT_POST(3)\fP to 0, libcurl resets the request type to the
default to disable the POST. Typically that means gets reset to GET. Instead
you should set a new request type explicitly as described above.
.SH DEFAULT
0, disabled
.SH PROTOCOLS
This functionality affects http only
.SH EXAMPLE
.nf
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/foo.bin");
    curl_easy_setopt(curl, CURLOPT_POST, 1L);

    /* set up the read callback with CURLOPT_READFUNCTION */

    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);
  }
}
.fi
.SH AVAILABILITY
Added in curl 7.1
.SH RETURN VALUE
Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.
.SH SEE ALSO
.BR CURLOPT_HTTPPOST (3),
.BR CURLOPT_POSTFIELDS (3),
.BR CURLOPT_UPLOAD (3)