CURLOPT_COPYPOSTFIELDS(3) Library Functions Manual CURLOPT_COPYPOSTFIELDS(3)
NAME
CURLOPT_COPYPOSTFIELDS - have libcurl copy data to POST
SYNOPSIS
#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_COPYPOSTFIELDS, char *data);
DESCRIPTION
Pass a char pointer as parameter, which should be the full data to post
in a HTTP POST operation. It behaves as the CURLOPT_POSTFIELDS(3) op-
tion, but the original data is instead copied by the library, allowing
the application to overwrite the original data after setting this op-
tion.
Because data is copied, care must be taken when using this option in
conjunction with CURLOPT_POSTFIELDSIZE(3) or CURLOPT_POSTFIELD-
SIZE_LARGE(3). If the size has not been set prior to CURLOPT_COPYPOST-
FIELDS(3), the data is assumed to be a null-terminated string; else the
stored size informs the library about the byte count to copy. In any
case, the size must not be changed after CURLOPT_COPYPOSTFIELDS(3), un-
less another CURLOPT_POSTFIELDS(3) or CURLOPT_COPYPOSTFIELDS(3) option
is set.
The application does not have to keep the string around after setting
this option.
Using this option multiple times makes the last set string override the
previous ones. Set it to NULL to disable its use again.
DEFAULT
NULL
PROTOCOLS
This functionality affects http only
EXAMPLE
int main(void)
{
CURL *curl = curl_easy_init();
if(curl) {
char local_buffer[1024]="data to send";
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
/* size of the data to copy from the buffer and send in the request */
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE, 12L);
/* send data from the local stack */
curl_easy_setopt(curl, CURLOPT_COPYPOSTFIELDS, local_buffer);
curl_easy_perform(curl);
}
}
AVAILABILITY
Added in curl 7.17.1
RETURN VALUE
curl_easy_setopt(3) returns a CURLcode indicating success or error.
CURLE_OK (0) means everything was OK, non-zero means an error occurred,
see libcurl-errors(3).
SEE ALSO
CURLOPT_MIMEPOST(3), CURLOPT_POSTFIELDS(3), CURLOPT_POSTFIELDSIZE(3),
CURLOPT_UPLOAD(3)
libcurl 2026-07-12 CURLOPT_COPYPOSTFIELDS(3)
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