curl / libcurl / API / curl_easy_setopt / CURLOPT_MIME_OPTIONS

CURLOPT_MIME_OPTIONS explained

Name

CURLOPT_MIME_OPTIONS - set MIME option flags

Synopsis

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

Description

Pass a long that holds a bitmask of CURLMIMEOPT_* defines. Each bit is a Boolean flag used while encoding a MIME tree or multipart form data.

Available bits are:

CURLMIMEOPT_FORMESCAPE

Tells libcurl to escape multipart form field and filenames using the backslash-escaping algorithm rather than percent-encoding (HTTP only).

Backslash-escaping consists in preceding backslashes and double quotes with a backslash. Percent encoding maps all occurrences of double quote, carriage return and line feed to %22, %0D and %0A respectively.

Before version 7.81.0, percent-encoding was never applied.

HTTP browsers used to do backslash-escaping in the past but have over time transitioned to use percent-encoding. This option allows one to address server-side applications that have not yet have been converted.

As an example, consider field or filename strangename"kind. When the containing multipart form is sent, this is normally transmitted as strangename%22kind. When this option is set, it is sent as strangename"kind.

Default

0, meaning disabled.

Protocols

This functionality affects http, imap and smtp

Example

int main(void)
{
  CURL *curl = curl_easy_init();
  curl_mime *form = NULL;
 
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
    curl_easy_setopt(curl, CURLOPT_MIME_OPTIONS, CURLMIMEOPT_FORMESCAPE);
 
    form = curl_mime_init(curl);
    if(form) {
      curl_mimepart *part = curl_mime_addpart(form);
 
      if(part) {
        curl_mime_filedata(part, "strange\\file\\name");
        curl_mime_name(part, "strange\"field\"name");
        curl_easy_setopt(curl, CURLOPT_MIMEPOST, form);
 
        /* Perform the request */
        curl_easy_perform(curl);
      }
    }
 
    curl_easy_cleanup(curl);
    curl_mime_free(form);
  }
}

Availability

Added in curl 7.81.0

Return value

Returns CURLE_OK