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CURLOPT_POSTFIELDSIZE_LARGE(3)

CURLOPT_POSTFIELDSIZE_LARGE - size of POST data pointed to

CURLOPT_POSTFIELDSIZE_LARGE(3) Library Functions Manual CURLOPT_POSTFIELDSIZE_LARGE(3)

CURLOPT_POSTFIELDSIZE_LARGE - size of POST data pointed to

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_POSTFIELDSIZE_LARGE,

curl_off_t size);

Set the size of the data buffer to POST to prevent libcurl from doing a strlen() to figure out the data size. When this option is used you can post fully binary data, which otherwise is likely to fail. If this size is set to -1, libcurl uses strlen() to get the size or relies on the CURLOPT_READFUNCTION(3) (if used) to signal the end of data.

You must make sure that the set size is not larger than the provided buffer.

-1

This functionality affects http, mqtt and rtsp

extern char *large_chunk; /* pointer to somewhere */
int main(void)
{

CURL *curl = curl_easy_init();
if(curl) {
CURLcode result;
const char *data = large_chunk;
curl_off_t length_of_data = 12345; /* set somehow */
curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
/* size of the POST data */
curl_easy_setopt(curl, CURLOPT_POSTFIELDSIZE_LARGE, length_of_data);
curl_easy_setopt(curl, CURLOPT_POSTFIELDS, data);
result = curl_easy_perform(curl);
curl_easy_cleanup(curl);
} }

Added in curl 7.11.1

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).

CURLOPT_COPYPOSTFIELDS(3), CURLOPT_POSTFIELDS(3), CURLOPT_POSTFIELDSIZE(3)

2026-10-19 libcurl

curl 8.23.0-r1 · os · ingested 2026-10-20