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

int main(void)
{
  CURL *curl;
  CURLcode res;

  /* In windows,this will init the winsock stuff */
  curl_global_init(CURL_GLOBAL_ALL);

  /* get a curl handle */
  curl = curl_easy_init();
  if(curl) {
    /* First set the URL that is about to receive our POST. This URL can
       just as well be a https:// URL if that is what should receive the
       data. */
    curl_easy_setopt(curl,CURLOPT_URL,"http://postit.example.com/moo.cgi");
    /* Now specify the POST data */
    curl_easy_setopt(curl,CURLOPT_POSTFIELDS,"name=daniel&project=curl");

    /* Perform the request,res will get the return code */
    res = curl_easy_perform(curl);
    /* Check for errors */
    if(res != CURLE_OK)
      fprintf(stderr,"curl_easy_perform() Failed: %s\n",curl_easy_strerror(res));

    /* always cleanup */
    curl_easy_cleanup(curl);
  }
  curl_global_cleanup();
  return 0;
}

3、libcurl之Multi Post

#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;

  struct curl_httppost *formpost=NULL;
  struct curl_httppost *lastptr=NULL;
  struct curl_slist *headerlist=NULL;
  static const char buf[] = "Expect:";

  /* Fill in the file upload field. This makes libcurl load data from
     the given file name when curl_easy_perform() is called. */
  curl_formadd(&formpost,&lastptr,CURLFORM_COPYNAME,"sendfile",CURLFORM_FILE,"postit2.c",CURLFORM_END);

  /* Fill in the filename field */
  curl_formadd(&formpost,"filename",CURLFORM_COPYCONTENTS,CURLFORM_END);

  /* Fill in the submit field too,even if this is rarely needed */
  curl_formadd(&formpost,"submit","send",CURLFORM_END);

  curl = curl_easy_init();
  multi_handle = curl_multi_init();

  /* initalize custom header list (stating that Expect: 100-continue is not
     wanted */
  headerlist = curl_slist_append(headerlist,buf);
  if(curl && multi_handle) {

    /* what URL that receives this POST */
    curl_easy_setopt(curl,"http://www.example.com/upload.cgi");
    curl_easy_setopt(curl,CURLOPT_VERBOSE,1L);

    curl_easy_setopt(curl,CURLOPT_HTTPHEADER,headerlist);
    curl_easy_setopt(curl,CURLOPT_HTTPPOST,formpost);

    curl_multi_add_handle(multi_handle,curl);

    curl_multi_perform(multi_handle,&still_running);

    do {
      struct timeval timeout;
      int rc; /* select() return code */

      fd_set fdread;
      fd_set fdwrite;
      fd_set fdexcep;
      int maxfd = -1;

      long curl_timeo = -1;

      FD_ZERO(&fdread);
      FD_ZERO(&fdwrite);
      FD_ZERO(&fdexcep);

      /* set a suitable timeout to play around with */
      timeout.tv_sec = 1;
      timeout.tv_usec = 0;

      curl_multi_timeout(multi_handle,&curl_timeo);
      if(curl_timeo >= 0) {
        timeout.tv_sec = curl_timeo / 1000;
        if(timeout.tv_sec > 1)
          timeout.tv_sec = 1;
        else
          timeout.tv_usec = (curl_timeo % 1000) * 1000;
      }

      /* get file descriptors from the transfers */
      curl_multi_fdset(multi_handle,&fdread,&fdwrite,&fdexcep,&maxfd);

      /* In a real-world program you OF COURSE check the return code of the
         function calls.  On success,the value of maxfd is guaranteed to be
         greater or equal than -1.  We call select(maxfd + 1,...),specially in
         case of (maxfd == -1),we call select(0,which is basically equal
         to sleep. */

      rc = select(maxfd+1,&timeout);

      switch(rc) {
      case -1:
        /* select error */
        break;
      case 0:
      default:
        /* timeout or readable/writable sockets */
        printf("perform!\n");
        curl_multi_perform(multi_handle,&still_running);
        printf("running: %d!\n",still_running);
        break;
      }
    } while(still_running);

    curl_multi_cleanup(multi_handle);

    /* always cleanup */
    curl_easy_cleanup(curl);

    /* then cleanup the formpost chain */
    curl_formfree(formpost);

    /* free slist */
    curl_slist_free_all (headerlist);
  }
  return 0;
}