Pass a char * as parameter, pointing to the full data to send in a 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 behaviour can be changed (so libcurl does copy the data) by setting the
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 CURLOPT_HTTPHEADER(3).
Using CURLOPT_POSTFIELDS(3) implies CURLOPT_POST(3).
You can use curl_easy_escape(3) to url-encode your data, if necessary. It
returns a pointer to an encoded string that can be passed as postdata.
If you want to do a zero-byte POST, you need to set
CURLOPT_POSTFIELDSIZE(3) explicitly to zero, as simply setting
CURLOPT_POSTFIELDS(3) to NULL or "" just effectively disables the
sending of the specified string. libcurl will instead assume that youll send
the POST data using the read callback!
Using POST with HTTP 1.1 implies the use of a "Expect: 100-continue" header.
You can disable this header with CURLOPT_HTTPHEADER(3) as usual.
To make multipart/formdata posts (aka RFC2388-posts), check out the
CURLOPT_HTTPPOST(3) option combined with curl_formadd(3).
CURL *curl = curl_easy_init();
const char *data = "data to send";
curl_easy_setopt(curl, CURLOPT_URL, "http://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);