docs/libcurl/opts/CURLOPT_POSTFIELDS.3

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.TH CURLOPT_POSTFIELDS 3 "April 23, 2021" "libcurl 7.78.0" "curl_easy_setopt options"

.SH NAME
CURLOPT_POSTFIELDS \- specify data to POST to server
.SH SYNOPSIS
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDS, char *postdata);
.SH DESCRIPTION
Pass a char * as parameter, pointing to the full data to send in an HTTP POST
operation. You must make sure that the data is formatted the way you want the
server to receive it. libcurl will not convert or encode it for you in any
way. For example, the web server may assume that this data is url-encoded.

The data pointed to is NOT copied by the library: as a consequence, it must be
preserved by the calling application until the associated transfer finishes.
This behavior can be changed (so libcurl does copy the data) by setting the
\fICURLOPT_COPYPOSTFIELDS(3)\fP option.

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 commonly
used by HTML forms. Change Content-Type with \fICURLOPT_HTTPHEADER(3)\fP.

You can use \fIcurl_easy_escape(3)\fP to url-encode your data, if necessary. It
returns a pointer to an encoded string that can be passed as \fIpostdata\fP.

Using \fICURLOPT_POSTFIELDS(3)\fP implies setting \fICURLOPT_POST(3)\fP to 1.

If \fICURLOPT_POSTFIELDS(3)\fP is explicitly set to NULL then libcurl will get
the POST data from the read callback. If you want to send a zero-byte POST set
\fICURLOPT_POSTFIELDS(3)\fP to an empty string, or set \fICURLOPT_POST(3)\fP to
1 and \fICURLOPT_POSTFIELDSIZE(3)\fP to 0.

libcurl will use assume this option points to a nul-terminated string unless
you also set \fICURLOPT_POSTFIELDSIZE(3)\fP to specify the length of the
provided data, which then is strictly required if you want to send off nul
bytes included in the data.

Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header,
and libcurl will add that header automatically if the POST is either known to
be larger than 1MB or if the expected size is unknown. You can disable this
header with \fICURLOPT_HTTPHEADER(3)\fP as usual.

To make multipart/formdata posts (aka RFC2388-posts), check out the
\fICURLOPT_HTTPPOST(3)\fP option combined with \fIcurl_formadd(3)\fP.
.SH DEFAULT
NULL
.SH PROTOCOLS
HTTP
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
  const char *data = "data to send";

  curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

  /* size of the POST data */
  curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, 12L);

  /* pass in a pointer to the data - libcurl will not copy */
  curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);

  curl_easy_perform(curl);
}
.fi
.SH AVAILABILITY
Always
.SH RETURN VALUE
Returns CURLE_OK
.SH "SEE ALSO"
.BR CURLOPT_POSTFIELDSIZE "(3), " CURLOPT_READFUNCTION "(3), "