CURLOPT_HTTPHEADER(3)

1CURLOPT_HTTPHEADER(3)      curl_easy_setopt options      CURLOPT_HTTPHEADER(3)
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NAME

6       CURLOPT_HTTPHEADER - set custom HTTP headers
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SYNOPSIS

9       #include <curl/curl.h>
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11       CURLcode   curl_easy_setopt(CURL  *handle,  CURLOPT_HTTPHEADER,  struct
12       curl_slist *headers);
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DESCRIPTION

15       Pass a pointer to a linked list of HTTP headers to pass to  the  server
16       and/or  proxy  in your HTTP request. The same list can be used for both
17       host and proxy requests!
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19       The linked list should be a  fully  valid  list  of  struct  curl_slist
20       structs properly filled in. Use curl_slist_append(3) to create the list
21       and curl_slist_free_all(3) to clean up an entire list.  If  you  add  a
22       header that is otherwise generated and used by libcurl internally, your
23       added one will be used instead. If you add a header with no content  as
24       in  'Accept:'  (no data on the right side of the colon), the internally
25       used header will get disabled. With this option you can add  new  head‐
26       ers,  replace  internal  headers  and remove internal headers. To add a
27       header with no content (nothing to the right side of  the  colon),  use
28       the form 'MyHeader;' (note the ending semicolon).
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30       The  headers  included  in the linked list must not be CRLF-terminated,
31       because libcurl adds CRLF after each header  item.  Failure  to  comply
32       with  this  will  result  in  strange bugs because the server will most
33       likely ignore part of the headers you specified.
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35       The first line in a request (containing the method, usually  a  GET  or
36       POST)  is  not  a header and cannot be replaced using this option. Only
37       the lines following the request-line are headers.  Adding  this  method
38       line  in  this  list of headers will only cause your request to send an
39       invalid header. Use CURLOPT_CUSTOMREQUEST(3) to change the method.
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41       When this option is passed to  curl_easy_setopt(3),  libcurl  will  not
42       copy the entire list so you must keep it around until you no longer use
43       this handle for a transfer before you  call  curl_slist_free_all(3)  on
44       the list.
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46       Pass a NULL to this option to reset back to no custom headers.
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48       The most commonly replaced headers have "shortcuts" in the options CUR‐
49       LOPT_COOKIE(3), CURLOPT_USERAGENT(3) and CURLOPT_REFERER(3). We  recom‐
50       mend using those.
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52       There's  an  alternative  option that sets or replaces headers only for
53       requests that are sent with CONNECT to a proxy: CURLOPT_PROXYHEADER(3).
54       Use CURLOPT_HEADEROPT(3) to control the behavior.
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SECURITY CONCERNS

57       By  default,  this  option  makes libcurl send the given headers in all
58       HTTP requests done by this handle. You should therefore use this option
59       with  caution  if  you  for  example connect to the remote site using a
60       proxy and a CONNECT request, you should to consider if  that  proxy  is
61       supposed to also get the headers. They may be private or otherwise sen‐
62       sitive to leak.
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64       Use CURLOPT_HEADEROPT(3) to make the headers only get sent to where you
65       intend them to get sent.
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67       Custom headers are sent in all requests done by the easy handles, which
68       implies that if you tell libcurl to follow redirects (CURLOPT_FOLLOWLO‐
69       CATION(3)),  the  same set of custom headers will be sent in the subse‐
70       quent request. Redirects can of course go to other hosts and thus those
71       servers will get all the contents of your custom headers too.
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73       Starting  in 7.58.0, libcurl will specifically prevent "Authorization:"
74       headers from being sent to other hosts than the first used one,  unless
75       specifically permitted with the CURLOPT_UNRESTRICTED_AUTH(3) option.
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77       Starting in 7.64.0, libcurl will specifically prevent "Cookie:" headers
78       from being sent to other hosts than the first used one, unless specifi‐
79       cally permitted with the CURLOPT_UNRESTRICTED_AUTH(3) option.
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DEFAULT

82       NULL
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PROTOCOLS

85       HTTP
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EXAMPLE

88       CURL *curl = curl_easy_init();
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90       struct curl_slist *list = NULL;
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92       if(curl) {
93         curl_easy_setopt(curl, CURLOPT_URL, "http://example.com");
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95         list = curl_slist_append(list, "Shoesize: 10");
96         list = curl_slist_append(list, "Accept:");
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98         curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);
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100         curl_easy_perform(curl);
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102         curl_slist_free_all(list); /* free the list again */
103       }
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AVAILABILITY

107       As long as HTTP is enabled
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RETURN VALUE

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