Curl retry with pipe

main.c

#include <stdio.h>
#include <stdlib.h>
#include <unistd.h>
 
#include <curl/curl.h>

size_t bytes_written = 0;
 
static size_t write_data(void *ptr, size_t size, size_t nmemb, void *stream)
{
  size_t written = fwrite(ptr, size, nmemb, (FILE *)stream);
  bytes_written += written;
  return written;
}
 
int main(int argc, char *argv[])
{
  CURL *curl_handle;
  CURLcode return_code;
 
  if(argc < 2) {
    printf("Usage: %s <URL>\n", argv[0]);
    return 1;
  }
 
  curl_global_init(CURL_GLOBAL_ALL);
  curl_handle = curl_easy_init();
 
  curl_easy_setopt(curl_handle, CURLOPT_URL, argv[1]);
  curl_easy_setopt(curl_handle, CURLOPT_VERBOSE, 1L);
  curl_easy_setopt(curl_handle, CURLOPT_NOPROGRESS, 0L);
  curl_easy_setopt(curl_handle, CURLOPT_WRITEFUNCTION, write_data);
  curl_easy_setopt(curl_handle, CURLOPT_WRITEDATA, stdout);
 
  return_code = curl_easy_perform(curl_handle);
  while (return_code != CURLE_OK)
  {
    size_t old = bytes_written;
    curl_easy_setopt(curl_handle, CURLOPT_RESUME_FROM_LARGE, bytes_written);

    if (old == bytes_written)
    {
        curl_easy_cleanup(curl_handle);
        curl_global_cleanup();
        printf("Received no bytes on retry, exiting.");
        return 2;
    }
    return_code = curl_easy_perform(curl_handle);
  }
 
  curl_easy_cleanup(curl_handle);
  curl_global_cleanup();
  return 0;
}