Ubuntu Manpage: CURLOPT_HTTPHEADER

Provided by: libcurl4-doc_8.9.1-2ubuntu2.1_all

NAME

       CURLOPT_HTTPHEADER - set of 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!

When used within an IMAP or SMTP request to upload a MIME mail, the given header list
establishes the document-level MIME headers to prepend to the uploaded document described
by CURLOPT_MIMEPOST(3). This does not affect raw mail uploads.

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 header is 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 is
disabled/removed. 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 'name;' (note the ending semicolon).

The headers included in the linked list must not be CRLF-terminated, because libcurl adds
CRLF after each header item itself. Failure to comply with this might result in strange
behavior. libcurl passes on the verbatim strings you give it, without any filter or other
safe guards. That includes white space and control characters.

The first line in an HTTP 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 only causes 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 does 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 HTTP headers have "shortcuts" in the options CURLOPT_COOKIE(3),
CURLOPT_USERAGENT(3) and CURLOPT_REFERER(3). We recommend using those.

There is 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.

SPECIFIC HTTP HEADERS

       Setting some specific headers causes libcurl to act differently.

       Host:  The specified hostname is used for cookie matching if the  cookie  engine  is  also
              enabled for this transfer. If the request is done over HTTP/2 or HTTP/3, the custom
              hostname is instead used in the ":authority" header field and Host: is not sent  at
              all over the wire.

       Transfer-Encoding: chunked
              Tells  libcurl  the  upload  is  to  be done using this chunked encoding instead of
              providing the Content-Length: field in the request.

SPECIFIC MIME HEADERS

       When used to build a MIME email for IMAP or SMTP, the following document-level headers can
       be set to override libcurl-generated values:

       Mime-Version:
              Tells  the  parser  at  the  receiving  site how to interpret the MIME framing.  It
              defaults to "1.0" and should normally not be altered.

       Content-Type:
              Indicates the document's global structure type. By  default,  libcurl  sets  it  to
              "multipart/mixed",  describing  a  document  made of independent parts. When a MIME
              mail is only composed of alternative representations of the same data  (i.e.:  HTML
              and  plain text), this header must be set to "multipart/alternative".  In all cases
              the value must be of the form "multipart/*" to respect the document  structure  and
              may not include the "boundary=" parameter.

       Other  specific  headers that do not have a libcurl default value but are strongly desired
       by mail delivery and user agents should also be included.  These are From:, To:, Date: and
       Subject:  among  others  and  their  presence  and value is generally checked by anti-spam
       utilities.

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 handle, which implies that if you
       tell libcurl to follow redirects  (CURLOPT_FOLLOWLOCATION(3)),  the  same  set  of  custom
       headers  is  sent in the subsequent request. Redirects can of course go to other hosts and
       thus those servers get all the contents of your custom headers too.

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

       Starting in 7.64.0, libcurl specifically prevents "Cookie:" 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

       This functionality affects http, imap and smtp

EXAMPLE

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

         struct curl_slist *list = NULL;

         if(curl) {
           curl_easy_setopt(curl, CURLOPT_URL, "https://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 */
         }
       }

HISTORY

       Use for MIME mail added in 7.56.0.

AVAILABILITY

       Added in curl 7.1

RETURN VALUE

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