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* Copyright (C) 1998 - 2019, Daniel Stenberg, <daniel@haxx.se>, et al.
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* This software is licensed as described in the file COPYING, which
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* are also available at https://curl.haxx.se/docs/copyright.html.
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* furnished to do so, under the terms of the COPYING file.
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CURLOPT_HEADEROPT - set how to send HTTP headers #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_HEADEROPT, long bitmask); Pass a long that is a bitmask of options of how to deal with headers. The two mutually exclusive options are: CURLHEADER_UNIFIED - the headers specified in CURLOPT_HTTPHEADER(3) will be used in requests both to servers and proxies. With this option enabled, CURLOPT_PROXYHEADER(3) will not have any effect. CURLHEADER_SEPARATE - makes CURLOPT_HTTPHEADER(3) headers only get sent to a server and not to a proxy. Proxy headers must be set with CURLOPT_PROXYHEADER(3) to get used. Note that if a non-CONNECT request is sent to a proxy, libcurl will send both server headers and proxy headers. When doing CONNECT, libcurl will send CURLOPT_PROXYHEADER(3) headers only to the proxy and then CURLOPT_HTTPHEADER(3) headers only to the server. CURLHEADER_SEPARATE (changed in 7.42.1, used CURLHEADER_UNIFIED before then) HTTP

CURL *curl = curl_easy_init();
if(curl) {
 CURLcode ret;
 struct curl_slist *list;
 list = curl_slist_append(NULL, "Shoesize: 10");
 list = curl_slist_append(list, "Accept:");
 curl_easy_setopt(curl, CURLOPT_URL, "https://example.com/");
 curl_easy_setopt(curl, CURLOPT_PROXY, "http://localhost:8080");
 curl_easy_setopt(curl, CURLOPT_HTTPHEADER, list);

 /* HTTPS over a proxy makes a separate CONNECT to the proxy, so tell
 libcurl to not send the custom headers to the proxy. Keep them
 separate! */
 curl_easy_setopt(curl, CURLOPT_HEADEROPT, CURLHEADER_SEPARATE);
 ret = curl_easy_perform(curl);
 curl_slist_free_all(list);
 curl_easy_cleanup(curl);
}

Added in 7.37.0 Returns CURLE_OK if the option is supported, and CURLE_UNKNOWN_OPTION if not. CURLOPT_HTTPHEADER "(3), " CURLOPT_PROXYHEADER "(3), "