Ubuntu Manpage: CURLOPT_HTTPHEADER - set custom HTTP headers

name
synopsis
description
security concerns
default
protocols
example
availability
return value
see also

Provided by: libcurl4-doc_7.58.0-2ubuntu3.24_all

NAME

       CURLOPT_HTTPHEADER - set custom HTTP headers

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HTTPHEADER, struct curl_slist *headers);

DESCRIPTION

Pass a pointer to a linked list of HTTP headers to pass to the server and/or proxy in your HTTP request.
The same list can be used for both host and proxy requests!

The linked list should be a fully valid list of struct curl_slist structs properly filled in. Use
curl_slist_append(3) to create the list and curl_slist_free_all(3) to clean up an entire list. If you add
a header that is otherwise generated and used by libcurl internally, your added one will be used instead.
If you add a header with no content as in 'Accept:' (no data on the right side of the colon), the
internally used header will get disabled. With this option you can add new headers, replace internal
headers and remove internal headers. To add a header with no content (nothing to the right side of the
colon), use the form 'MyHeader;' (note the ending semicolon).

The headers included in the linked list must not be CRLF-terminated, because libcurl adds CRLF after each
header item. Failure to comply with this will result in strange bugs because the server will most likely
ignore part of the headers you specified.

The first line in a request (containing the method, usually a GET or POST) is not a header and cannot be
replaced using this option. Only the lines following the request-line are headers. Adding this method
line in this list of headers will only cause your request to send an invalid header. Use
CURLOPT_CUSTOMREQUEST(3) to change the method.

When this option is passed to curl_easy_setopt(3), libcurl will not copy the entire list so you must keep
it around until you no longer use this handle for a transfer before you call curl_slist_free_all(3) on
the list.

Pass a NULL to this option to reset back to no custom headers.

The most commonly replaced headers have "shortcuts" in the options CURLOPT_COOKIE(3),
CURLOPT_USERAGENT(3) and CURLOPT_REFERER(3). We recommend using those.

There's an alternative option that sets or replaces headers only for requests that are sent with CONNECT
to a proxy: CURLOPT_PROXYHEADER(3). Use CURLOPT_HEADEROPT(3) to control the behavior.

SECURITY CONCERNS

       By  default,  this  option makes libcurl send the given headers in all HTTP requests done by this handle.
       You should therefore use this option with caution if you for example connect to the remote site  using  a
       proxy  and  a  CONNECT request, you should to consider if that proxy is supposed to also get the headers.
       They may be private or otherwise sensitive to leak.

       Use CURLOPT_HEADEROPT(3) to make the headers only get sent to where you intend them to get sent.

       Custom headers are sent in all requests done by the easy handles, which implies that if you tell  libcurl
       to  follow  redirects  (CURLOPT_FOLLOWLOCATION(3)),  the  same  set of custom headers will be sent in the
       subsequent request. Redirects can of course go to other hosts and thus those servers  will  get  all  the
       contents of your custom headers too.

       Starting  in  7.58.0, libcurl will specifically prevent "Authorization:" headers from being sent to other
       hosts than the first used  one,  unless  specifically  permitted  with  the  CURLOPT_UNRESTRICTED_AUTH(3)
       option.

DEFAULT

       NULL

PROTOCOLS

       HTTP

EXAMPLE

       CURL *curl = curl_easy_init();

       struct curl_slist *list = NULL;

       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");

         list = curl_slist_append(list, "Shoesize: 10");
         list = curl_slist_append(list, "Accept:");

         curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);

         curl_easy_perform(curl);

         curl_slist_free_all(list); /* free the list again */
       }

AVAILABILITY

       As long as HTTP is enabled

RETURN VALUE

       Returns CURLE_OK if HTTP is supported, and CURLE_UNKNOWN_OPTION if not.