curl_mime_headers(3)

curl_mime_headers3

Set a mime part's custom headers

Usage

#include <curl/curl.h>
CURLcode curl_mime_headers(curl_mimepart *part,
                           struct curl_slist *headers, int take_ownership);

Overview

curl_mime_headers(3) sets a mime part's custom headers.

part is the part's handle to assign the custom headers list to.

headers is the head of a list of custom headers; it may be set to NULL to remove a previously attached custom header list.

take_ownership: when non-zero, causes the list to be freed upon replacement or mime structure deletion; in this case the list must not be freed explicitly.

Setting a part's custom headers list multiple times is valid: only the value set by the last call is retained.

Protocols

This functionality affects http, imap and smtp

Examples

int main(void)
{
  struct curl_slist *headers = NULL;
  CURL *easy = curl_easy_init();
  curl_mime *mime;
  curl_mimepart *part;
  headers = curl_slist_append(headers, "Custom-Header: mooo");
  mime = curl_mime_init(easy);
  part = curl_mime_addpart(mime);
  /* use these headers in the part, takes ownership */
  curl_mime_headers(part, headers, 1);
  /* pass on this data */
  curl_mime_data(part, "12345679", CURL_ZERO_TERMINATED);
  /* set name */
  curl_mime_name(part, "numbers");
  /* Post and send it. */
  curl_easy_setopt(easy, CURLOPT_MIMEPOST, mime);
  curl_easy_setopt(easy, CURLOPT_URL, "https://example.com");
  curl_easy_perform(easy);
}

Return value

This function returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3). If CURLOPT_ERRORBUFFER(3) was set with curl_easy_setopt(3) there can be an error message stored in the error buffer when non-zero is returned.

Releases

5 releases since Debian 10 (Buster); the text changed 4 times.

  1. 10
  2. 11
  3. 12
  4. 13
  5. Arch

Availability

Added in curl 7.56.0

From curl 8.23.0-1 in Arch Linux 2026-11-01. Parsed by carta from the page's man source.