curl_mime_type man page

#include <curl/curl.h>

CURLcode curl_mime_type(curl_mimepart * part, const char * mimetype);

curl_mime_type(3) sets a mime part's content type.

part is the part's handle to assign the content type to.

mimetype points to the nul-terminated file mime type string; it may be set to NULL to remove a previously attached mime type.

The mime type string is copied into the part, thus the associated storage may safely be released or reused after call. Setting a part's type twice is valid: only the value set by the last call is retained.

In the absence of a mime type and if needed by the protocol specifications, a default mime type is determined by the context:
- If set as a custom header, use this value.
- application/form-data for an HTTP form post.
- If a remote file name is set, the mime type is taken from the file name extension, or application/octet-stream by default.
- For a multipart part, multipart/mixed.
- text/plain in other cases.

As long as at least one of HTTP, SMTP or IMAP is enabled. Added in 7.56.0.

CURLE_OK or a CURL error code upon failure.

 curl_mime *mime;
 curl_mimepart *part;

 /* create a mime handle */
 mime = curl_mime_init(easy);

 /* add a part */
 part = curl_mime_addpart(mime);

 /* get data from this file */
 curl_mime_filedata(part, "image.png");

 /* content-type for this part */
 curl_mime_type(part, "image/png");

 /* set name */
 curl_mime_name(part, "image");

curl_mime_addpart(3), curl_mime_name(3), curl_mime_data(3)

curl_mime_addpart(3), curl_mime_data(3), curl_mime_name(3), libcurl-tutorial(3).