Non-blocking HTTP form-post

This examples makes a multipart form-post using the multi interface.

#include <stdio.h>#include <string.h>#include <sys/time.h>#include <curl/curl.h>int main(void){  CURL *curl;  CURLM *multi_handle;  int still_running = 0;  curl_mime *form = NULL;  curl_mimepart *field = NULL;  struct curl_slist *headerlist = NULL;  static const char buf[] = "Expect:";  curl = curl_easy_init();  multi_handle = curl_multi_init();  if(curl && multi_handle) {    /* Create the form */    form = curl_mime_init(curl);    /* Fill in the file upload field */    field = curl_mime_addpart(form);    curl_mime_name(field, "sendfile");    curl_mime_filedata(field, "multi-post.c");    /* Fill in the filename field */    field = curl_mime_addpart(form);    curl_mime_name(field, "filename");    curl_mime_data(field, "multi-post.c", CURL_ZERO_TERMINATED);    /* Fill in the submit field too, even if this is rarely needed */    field = curl_mime_addpart(form);    curl_mime_name(field, "submit");    curl_mime_data(field, "send", CURL_ZERO_TERMINATED);    /* initialize custom header list (stating that Expect: 100-continue is       not wanted */    headerlist = curl_slist_append(headerlist, buf);    /* what URL that receives this POST */    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/upload.cgi");    curl_easy_setopt(curl, CURLOPT_VERBOSE, 1L);    curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headerlist);    curl_easy_setopt(curl, CURLOPT_MIMEPOST, form);    curl_multi_add_handle(multi_handle, curl);    do {      CURLMcode mc = curl_multi_perform(multi_handle, &still_running);      if(still_running)        /* wait for activity, timeout or "nothing" */        mc = curl_multi_poll(multi_handle, NULL, 0, 1000, NULL);      if(mc)        break;    } while(still_running);    curl_multi_cleanup(multi_handle);    /* always cleanup */    curl_easy_cleanup(curl);    /* then cleanup the form */    curl_mime_free(form);    /* free slist */    curl_slist_free_all(headerlist);  }  return 0;}