CURLOPT_UPLOAD(3) Library Functions Manual CURLOPT_UPLOAD(3)

CURLOPT_UPLOAD - data upload

#include <curl/curl.h>
CURLcode curl_easy_setopt(CURL *handle, CURLOPT_UPLOAD, long upload);

The long parameter upload set to 1 tells the library to prepare for and perform an upload. The CURLOPT_READDATA(3) and CURLOPT_INFILESIZE(3) or CURLOPT_INFILESIZE_LARGE(3) options are also interesting for uploads. If the protocol is HTTP, uploading means using the PUT request unless you tell libcurl otherwise.

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

If you use PUT to an HTTP 1.1 server, you can upload data without knowing the size before starting the transfer. The library enables this by adding a header "Transfer-Encoding: chunked". With HTTP 1.0 or if you prefer not to use chunked transfer, you must specify the size of the data with CURLOPT_INFILESIZE(3) or CURLOPT_INFILESIZE_LARGE(3).

0, default is download


static size_t read_cb(char *ptr, size_t size, size_t nmemb, void *userdata)
  FILE *src = userdata;
  /* copy as much data as possible into the 'ptr' buffer, but no more than
     'size' * 'nmemb' bytes */
  size_t retcode = fread(ptr, size, nmemb, src);
  return retcode;
int main(void)
  CURL *curl = curl_easy_init();
  if(curl) {
    FILE *src = fopen("local-file", "r");
    curl_off_t fsize; /* set this to the size of the input file */
    /* we want to use our own read function */
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, read_cb);
    /* enable uploading */
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
    /* specify target */
    curl_easy_setopt(curl, CURLOPT_URL, "");
    /* now specify which pointer to pass to our callback */
    curl_easy_setopt(curl, CURLOPT_READDATA, src);
    /* Set the size of the file to upload */
    curl_easy_setopt(curl, CURLOPT_INFILESIZE_LARGE, (curl_off_t)fsize);
    /* Now run off and do what you have been told! */


Returns CURLE_OK


2024-05-22 libcurl