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* Copyright (C) 1998 - 2015, Daniel Stenberg, <daniel@haxx.se>, et al.
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CURLOPT_DEFAULT_PROTOCOL - default protocol to use if the URL is missing a scheme name #include <curl/curl.h> CURLcode curl_easy_setopt(CURL *handle, CURLOPT_DEFAULT_PROTOCOL, char *protocol); This option tells libcurl to use protocol if the URL is missing a scheme name. Use one of these protocol (scheme) names: dict, file, ftp, ftps, gopher, http, https, imap, imaps, ldap, ldaps, pop3, pop3s, rtsp, scp, sftp, smb, smbs, smtp, smtps, telnet, tftp An unknown or unsupported protocol causes error CURLE_UNSUPPORTED_PROTOCOL when libcurl parses a schemeless URL. Parsing happens when curl_easy_perform(3) or curl_multi_perform(3) is called. The protocols supported by libcurl will vary depending on how it was built. Use curl_version_info(3) if you need a list of protocol names supported by the build of libcurl that you are using. This option does not change the default proxy protocol (http). Without this option libcurl would make a guess based on the host, see CURLOPT_URL(3) for details. The application does not have to keep the string around after setting this option. NULL (make a guess based on the host) All

curl = curl_easy_init();
if(curl) {
 /* set a URL without a scheme */
 curl_easy_setopt(curl, CURLOPT_URL, "example.com");

 /* set the default protocol (scheme) for schemeless URLs */
 curl_easy_setopt(curl, CURLOPT_DEFAULT_PROTOCOL, "https");

 /* Perform the request */
 curl_easy_perform(curl);
}

Added in 7.45.0 CURLE_OK if the option is supported. CURLE_OUT_OF_MEMORY if there was insufficient heap space. CURLE_UNKNOWN_OPTION if the option is not supported. CURLOPT_URL "(3), "