---
name: "curl_mime_subparts"
section: "3"
platform: "linux"
package: "curl"
version: "8.23.0-1"
release: "Arch Linux 2026-11-01"
platforms: ["linux", "macos"]
url: "https://new.carta.tech/curl_mime_subparts"
---

# curl\_mime\_subparts(3)

set sub-parts of a multipart mime part

## NAME

curl\_mime\_subparts - set sub-parts of a multipart mime part

## SYNOPSIS

```
#include <curl/curl.h>
CURLcode curl_mime_subparts(curl_mimepart *part, curl_mime *subparts);
```

## DESCRIPTION

*[curl\_mime\_subparts(3)](/curl_mime_subparts/3.md)* sets a multipart mime part's content from a mime structure.

*part* is a handle to the multipart part.

*subparts* is a mime structure handle holding the sub-parts. After *[curl\_mime\_subparts(3)](/curl_mime_subparts/3.md)* succeeds, the mime structure handle belongs to the multipart part and must not be freed explicitly. It may however be updated by subsequent calls to mime API functions.

Setting a part's contents multiple times is valid: only the value set by the last call is retained. It is possible to unassign previous part's contents by setting *subparts* to NULL.

## PROTOCOLS

This functionality affects http, imap and smtp

## EXAMPLE

```
static const char *inline_html = "<title>example</title>";
static const char *inline_text = "once upon the time";
int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    struct curl_slist *slist;
    /* The inline part is an alternative proposing the html and the text
       versions of the email. */
    curl_mime *alt = curl_mime_init(curl);
    curl_mimepart *part;
    /* HTML message. */
    part = curl_mime_addpart(alt);
    curl_mime_data(part, inline_html, CURL_ZERO_TERMINATED);
    curl_mime_type(part, "text/html");
    /* Text message. */
    part = curl_mime_addpart(alt);
    curl_mime_data(part, inline_text, CURL_ZERO_TERMINATED);
    /* Create the inline part. */
    part = curl_mime_addpart(alt);
    curl_mime_subparts(part, alt);
    curl_mime_type(part, "multipart/alternative");
    slist = curl_slist_append(NULL, "Content-Disposition: inline");
    curl_mime_headers(part, slist, 1);
  }
}
```

## AVAILABILITY

Added in curl 7.56.0

## 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)](/libcurl-errors/3.md)*. If *[CURLOPT\_ERRORBUFFER(3)](/CURLOPT_ERRORBUFFER/3.md)* was set with *[curl\_easy\_setopt(3)](/curl_easy_setopt/3.md)* there can be an error message stored in the error buffer when non-zero is returned.

## SEE ALSO

[**curl\_mime\_addpart**(3)](/curl_mime_addpart/3.md), [**curl\_mime\_init**(3)](/curl_mime_init/3.md)