Daniel Stenberg e694c8284a

docs/libcurl/opts: clarify the return values

Expand a little.

- mention the type name of the return code
- avoid stating which exact return codes that might be returned, as that
  varies over time, builds and conditions
- avoid stating some always return OK
- refer to the manpage documenting all the return codes

Closes #15900

2025-01-02 17:13:33 +01:00

1.8 KiB

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SPDX-License-Identifier

Title

Section

Source

Protocol

See-also

Added-in

curl

CURLOPT_HEADER

libcurl

HTTP

FTP

IMAP

POP3

SMTP

CURLOPT_HEADERFUNCTION (3)

CURLOPT_HTTPHEADER (3)

7.1

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

%PROTOCOLS%

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%

RETURN VALUE

curl_easy_setopt(3) returns a CURLcode indicating success or error.

CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).

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