NAME

       curl_easy_header - get an HTTP header

SYNOPSIS

       #include <curl/curl.h>

       CURLHcode curl_easy_header(CURL *easy,
                                  const char *name,
                                  size_t index,
                                  unsigned int origin,
                                  int request,
                                  struct curl_header **hout);

DESCRIPTION

       curl_easy_header(3)  returns a pointer to a "curl_header" struct in hout with data for the
       HTTP response header name. The case insensitive  null-terminated  header  name  should  be
       specified without colon.

       index  0  means asking for the first instance of the header. If the returned header struct
       has amount set larger than 1, it means there are more instances of the  same  header  name
       available to get. Asking for a too big index makes CURLHE_BADINDEX get returned.

       The  origin argument is for specifying which headers to receive, as a single HTTP transfer
       might provide headers from several different places  and  they  may  then  have  different
       importance  to  the  user  and  headers using the same name might be used. The origin is a
       bitmask for what header sources you want. See the descriptions below.

       The request argument tells libcurl from which request you  want  headers  from.  A  single
       transfer  might  consist  of  a series of HTTP requests and this argument lets you specify
       which particular individual request you want the headers from. 0 being the  first  request
       and  then the number increases for further redirects or when multi-state authentication is
       used. Passing in -1 is a shortcut to "the last" request in the  series,  independently  of
       the actual amount of requests used.

       libcurl  stores  and  provides  the  actually  used  "correct" headers. If for example two
       headers with the same name arrive and the latter  overrides  the  former,  then  only  the
       latter  is  provided.  If the first header survives the second, then only the first one is
       provided. An application using this API does not have to  bother  about  multiple  headers
       used wrongly.

       The memory for the returned struct is associated with the easy handle and subsequent calls
       to curl_easy_header(3) clobbers the struct used in the previous calls for  the  same  easy
       handle.  Applications need to copy the data if it wants to keep it around. The memory used
       for the struct gets freed with calling curl_easy_cleanup(3) of the easy handle.

       The first line in an HTTP response is called the status  line.  It  is  not  considered  a
       header by this function. Headers are the "name: value" lines following the status.

       This function can be used before (all) headers have been received and is fine to call from
       within libcurl callbacks. It returns the state of the headers at the time it is called.

The header struct

       struct curl_header {
          char *name;
          char *value;
          size_t amount;
          size_t index;
          unsigned int origin;
          void *anchor;
       };

       The data name field points to, is the same  as  the  requested  name,  but  might  have  a
       different case.

       The  data  value  field  points  to,  comes exactly as delivered over the network but with
       leading and trailing whitespace and newlines stripped  off.  The  `value`  data  is  null-
       terminated. For legacy HTTP/1 "folded headers", this API provides the full single value in
       an unfolded manner with a single whitespace between the lines.

       amount is how many headers using this name that exist, within the origin and request scope
       asked for.

       index  is the zero based entry number of this particular header, which in case this header
       was used more than once in the requested scope can be larger than 0  but  is  always  less
       than amount.

       The  origin  field  in the "curl_header" struct has one of the origin bits set, indicating
       where from the header originates. At the time of this  writing,  there  are  5  bits  with
       defined  use.  The undocumented 27 remaining bits are reserved for future use and must not
       be assumed to have any particular value.

       anchor is a private handle used by libcurl internals. Do not modify.

ORIGINS

       CURLH_HEADER
              The header arrived as a header from the server.

       CURLH_TRAILER
              The header arrived as a trailer. A header that arrives after the body.

       CURLH_CONNECT
              The header arrived in a CONNECT response. A CONNECT request is being done to  setup
              a transfer "through" an HTTP(S) proxy.

       CURLH_1XX
              The  header  arrived  in  an HTTP 1xx response. A 1xx response is an "intermediate"
              response that might happen before the "real" response.

       CURLH_PSEUDO
              The header is an HTTP/2 or HTTP/3 pseudo header

EXAMPLE

       int main(void)
       {
         struct curl_header *type;
         CURL *curl = curl_easy_init();
         if(curl) {
           CURLHcode h;
           curl_easy_setopt(curl, CURLOPT_URL, "https://example.com");
           curl_easy_perform(curl);
           h = curl_easy_header(curl, "Content-Type", 0, CURLH_HEADER, -1, &type);
           curl_easy_cleanup(curl);
         }
       }

AVAILABILITY

       Added in 7.83.0. Officially supported since 7.84.0.

RETURN VALUE

       This function returns a CURLHcode indicating success or error.

SEE ALSO

       curl_easy_nextheader(3),          curl_easy_perform(3),          CURLINFO_CONTENT_TYPE(3),
       CURLOPT_HEADERFUNCTION(3), libcurl-errors(3)