curl/docs/libcurl/opts/CURLOPT_HEADER.md
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

1.6 KiB

c SPDX-License-Identifier Title Section Source See-also
Copyright (C) Daniel Stenberg, <daniel.se>, et al. curl CURLOPT_HEADER 3 libcurl
CURLOPT_HEADERFUNCTION (3)
CURLOPT_HTTPHEADER (3)

NAME

CURLOPT_HEADER - pass headers to the data stream

SYNOPSIS

#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADER, long onoff);

DESCRIPTION

Pass the long value onoff set to 1 to ask libcurl to include the headers in the write callback (CURLOPT_WRITEFUNCTION(3)). This option is relevant for protocols that actually have headers or other meta-data (like HTTP and FTP).

When asking to get the headers passed to the same callback as the body, it is not possible to accurately separate them again without detailed knowledge about the protocol in use.

Further: the CURLOPT_WRITEFUNCTION(3) callback is limited to only ever get a maximum of CURL_MAX_WRITE_SIZE bytes passed to it (16KB), while a header can be longer and the CURLOPT_HEADERFUNCTION(3) supports getting called with headers up to CURL_MAX_HTTP_HEADER bytes big (100KB).

It is often better to use CURLOPT_HEADERFUNCTION(3) to get the header data separately.

While named confusingly similar, CURLOPT_HTTPHEADER(3) is used to set custom HTTP headers!

DEFAULT

0

PROTOCOLS

Most

EXAMPLE

int main(void)
{
  CURL *curl = curl_easy_init();
  if(curl) {
    curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");

    curl_easy_setopt(curl, CURLOPT_HEADER, 1L);

    curl_easy_perform(curl);
  }
}

AVAILABILITY

Provided in all libcurl versions.

RETURN VALUE

Returns CURLE_OK.