curl / libcurl / API / curl_easy_setopt / CURLOPT_RESUME_FROM

CURLOPT_RESUME_FROM explained

Name

CURLOPT_RESUME_FROM - offset to resume transfer from

Synopsis

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

Description

Pass a long as parameter. It contains the offset in number of bytes that you want the transfer to start from. Set this option to 0 to make the transfer start from the beginning (effectively disabling resume). For FTP, set this option to -1 to make the transfer start from the end of the target file (useful to continue an interrupted upload).

When doing uploads with FTP, the resume position is where in the local/source file libcurl should try to resume the upload from and it then appends the source file to the remote target file.

HTTP uploads using POST or PUT cannot be resumed. curl_easy_perform returns CURLE_BAD_FUNCTION_ARGUMENT when this option is set to a non-zero value for such an upload.

If you need to resume a transfer beyond the 2GB limit, use CURLOPT_RESUME_FROM_LARGE instead.

Default

0, not used

Protocols

This functionality affects all supported protocols

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode result;
    long size_of_file = 6789;
 
    curl_easy_setopt(curl, CURLOPT_URL, "ftp://example.com");
 
    /* resume upload at byte index 200 */
    curl_easy_setopt(curl, CURLOPT_RESUME_FROM, 200L);
 
    /* ask for upload */
    curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
 
    /* set total data amount to expect */
    curl_easy_setopt(curl, CURLOPT_INFILESIZE, size_of_file);
 
    /* Perform the request */
    result = curl_easy_perform(curl);
    curl_easy_cleanup(curl);
  }
}

Availability

Added in curl 7.1

Return value

curl_easy_setopt returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors.