CURLOPT_HEADER(3) Library Functions Manual CURLOPT_HEADER(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 rele-
vant 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
This functionality affects ftp, http, imap, pop3 and smtp
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
Added in curl 7.1
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).
SEE ALSO
CURLOPT_HEADERFUNCTION(3), CURLOPT_HTTPHEADER(3)
libcurl 2026-07-12 CURLOPT_HEADER(3)
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