mirror of https://github.com/curl/curl.git synced 2024-12-09 06:30:06 +08:00

Daniel Stenberg eefcc1bda4

docs: introduce "curldown" for libcurl man page format

curldown is this new file format for libcurl man pages. It is markdown
inspired with differences:

- Each file has a set of leading headers with meta-data
- Supports a small subset of markdown
- Uses .md file extensions for editors/IDE/GitHub to treat them nicely
- Generates man pages very similar to the previous ones
- Generates man pages that still convert nicely to HTML on the website
- Detects and highlights mentions of curl symbols automatically (when
  their man page section is specified)

tools:

- cd2nroff: converts from curldown to nroff man page
- nroff2cd: convert an (old) nroff man page to curldown
- cdall: convert many nroff pages to curldown versions
- cd2cd: verifies and updates a curldown to latest curldown

This setup generates .3 versions of all the curldown versions at build time.

CI:

Since the documentation is now technically markdown in the eyes of many
things, the CI runs many more tests and checks on this documentation,
including proselint, link checkers and tests that make sure we capitalize the
first letter after a period...

Closes #12730

2024-01-23 00:29:02 +01:00

2.8 KiB

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SPDX-License-Identifier

Title

Section

Source

See-also

curl

CURLOPT_TRAILERFUNCTION

libcurl

CURLOPT_TRAILERDATA (3)

CURLOPT_WRITEFUNCTION (3)

NAME

CURLOPT_TRAILERFUNCTION - callback for sending trailing headers

SYNOPSIS

#include <curl.h>

int curl_trailer_callback(struct curl_slist ** list, void *userdata);

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_TRAILERFUNCTION,
                          curl_trailer_callback *func);

DESCRIPTION

Pass a pointer to a callback function.

This callback function is called once right before sending the final CR LF in an HTTP chunked transfer to fill a list of trailing headers to be sent before finishing the HTTP transfer.

You can set the userdata argument with the CURLOPT_TRAILERDATA(3) option.

The trailing headers included in the linked list must not be CRLF-terminated, because libcurl adds the appropriate line termination characters after each header item.

If you use curl_slist_append(3) to add trailing headers to the curl_slist then libcurl duplicates the strings, and frees the curl_slist once the trailers have been sent.

If one of the trailing header fields is not formatted correctly it is ignored and an info message is emitted.

The return value can either be CURL_TRAILERFUNC_OK or CURL_TRAILERFUNC_ABORT which would respectively instruct libcurl to either continue with sending the trailers or to abort the request.

If you set this option to NULL, then the transfer proceeds as usual without any interruptions.

DEFAULT

NULL

PROTOCOLS

HTTP

EXAMPLE

static int trailer_cb(struct curl_slist **tr, void *data)
{
  /* libcurl frees the list */
  *tr = curl_slist_append(*tr, "My-super-awesome-trailer: trailer-stuff");
  return CURL_TRAILERFUNC_OK;
}

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    CURLcode res;

    /* Set the URL of the request */
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
    /* Now set it as a put */
    curl_easy_setopt(curl, CURLOPT_PUT, 1L);

    /* Assuming we have a function that returns the data to be pushed
       Let that function be read_cb */
    curl_easy_setopt(curl, CURLOPT_READFUNCTION, trailer_cb);

    struct curl_slist *headers = NULL;
    headers = curl_slist_append(headers, "Trailer: My-super-awesome-trailer");
    res = curl_easy_setopt(curl, CURLOPT_HTTPHEADER, headers);

    /* Set the trailers filling callback */
    curl_easy_setopt(curl, CURLOPT_TRAILERFUNCTION, trailer_cb);

    /* Perform the transfer */
    res = curl_easy_perform(curl);

    curl_easy_cleanup(curl);

    curl_slist_free_all(headers);
  }
}

AVAILABILITY

This option was added in curl 7.64.0 and is present if HTTP support is enabled.

RETURN VALUE

Returns CURLE_OK.

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