text: /***************************************************************************
   *                                  _   _ ____  _
   *  Project                     ___| | | |  _ \| |
   *                             / __| | | | |_) | |
   *                            | (__| |_| |  _ <| |___
   *                             \___|\___/|_| \_\_____|
   *
   * Copyright (C) 1998 - 2016, Daniel Stenberg, <daniel@haxx.se>, et al.
   *
   * This software is licensed as described in the file COPYING, which
   * you should have received as part of this distribution. The terms
   * are also available at https://curl.haxx.se/docs/copyright.html.
   *
   * You may opt to use, copy, modify, merge, publish, distribute and/or sell
   * copies of the Software, and permit persons to whom the Software is
   * furnished to do so, under the terms of the COPYING file.
   *
   * This software is distributed on an "AS IS" basis, WITHOUT WARRANTY OF ANY
   * KIND, either express or implied.
   *
   ***************************************************************************/
  
  /* <DESC>
   * SMTP example showing how to send e-mails
   * </DESC>
   */
  
  #include <stdio.h>
  #include <string.h>
  #include <curl/curl.h>
  
  /* This is a simple example showing how to send mail using libcurl's SMTP
   * capabilities. For an example of using the multi interface please see
   * smtp-multi.c.
   *
   * Note that this example requires libcurl 7.20.0 or above.
   */
  
  #define FROM    "<sender@example.org>"
  #define TO      "<addressee@example.net>"
  #define CC      "<info@example.org>"
  
  static const char *payload_text[] = {
    "Date: Mon, 29 Nov 2010 21:54:29 +1100\r\n",
    "To: " TO "\r\n",
    "From: " FROM "(Example User)\r\n",
    "Cc: " CC "(Another example User)\r\n",
    "Message-ID: <dcd7cb36-11db-487a-9f3a-e652a9458efd@"
    "rfcpedant.example.org>\r\n",
    "Subject: SMTP example message\r\n",
    "\r\n", /* empty line to divide headers from body, see RFC5322 */
    "The body of the message starts here.\r\n",
    "\r\n",
    "It could be a lot of lines, could be MIME encoded, whatever.\r\n",
    "Check RFC5322.\r\n",
    NULL
  };
  
  struct upload_status {
    int lines_read;
  };
  
  static size_t payload_source(void *ptr, size_t size, size_t nmemb, void *userp)
  {
    struct upload_status *upload_ctx = (struct upload_status *)userp;
    const char *data;
  
    if((size == 0) || (nmemb == 0) || ((size*nmemb) < 1)) {
      return 0;
    }
  
    data = payload_text[upload_ctx->lines_read];
  
    if(data) {
      size_t len = strlen(data);
      memcpy(ptr, data, len);
      upload_ctx->lines_read++;
  
      return len;
    }
  
    return 0;
  }
  
  int main(void)
  {
    CURL *curl;
    CURLcode res = CURLE_OK;
    struct curl_slist *recipients = NULL;
    struct upload_status upload_ctx;
  
    upload_ctx.lines_read = 0;
  
    curl = curl_easy_init();
    if(curl) {
      /* This is the URL for your mailserver */
      curl_easy_setopt(curl, CURLOPT_URL, "smtp://mail.example.com");
  
      /* Note that this option isn't strictly required, omitting it will result
       * in libcurl sending the MAIL FROM command with empty sender data. All
       * autoresponses should have an empty reverse-path, and should be directed
       * to the address in the reverse-path which triggered them. Otherwise,
       * they could cause an endless loop. See RFC 5321 Section 4.5.5 for more
       * details.
       */
      curl_easy_setopt(curl, CURLOPT_MAIL_FROM, FROM);
  
      /* Add two recipients, in this particular case they correspond to the
       * To: and Cc: addressees in the header, but they could be any kind of
       * recipient. */
      recipients = curl_slist_append(recipients, TO);
      recipients = curl_slist_append(recipients, CC);
      curl_easy_setopt(curl, CURLOPT_MAIL_RCPT, recipients);
  
      /* We're using a callback function to specify the payload (the headers and
       * body of the message). You could just use the CURLOPT_READDATA option to
       * specify a FILE pointer to read from. */
      curl_easy_setopt(curl, CURLOPT_READFUNCTION, payload_source);
      curl_easy_setopt(curl, CURLOPT_READDATA, &upload_ctx);
      curl_easy_setopt(curl, CURLOPT_UPLOAD, 1L);
  
      /* Send the message */
      res = curl_easy_perform(curl);
  
      /* Check for errors */
      if(res != CURLE_OK)
        fprintf(stderr, "curl_easy_perform() failed: %s\n",
                curl_easy_strerror(res));
  
      /* Free the list of recipients */
      curl_slist_free_all(recipients);
  
      /* curl won't send the QUIT command until you call cleanup, so you should
       * be able to re-use this connection for additional messages (setting
       * CURLOPT_MAIL_FROM and CURLOPT_MAIL_RCPT as required, and calling
       * curl_easy_perform() again. It may not be a good idea to keep the
       * connection open for a very long time though (more than a few minutes
       * may result in the server timing out the connection), and you do want to
       * clean up in the end.
       */
      curl_easy_cleanup(curl);
    }
  
    return (int)res;
  }
  