Provided by: libcurl4-doc_7.58.0-2ubuntu3.24_all bug


       CURLOPT_PROXY - set proxy to use


       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PROXY, char *proxy);


       Set  the proxy to use for the upcoming request. The parameter should be a char * to a zero
       terminated string holding the host name or dotted numerical IP address. A  numerical  IPv6
       address must be written within [brackets].

       To  specify  port  number  in this string, append :[port] to the end of the host name. The
       proxy's  port  number   may   optionally   be   specified   with   the   separate   option
       CURLOPT_PROXYPORT(3).  If  not  specified,  libcurl  will  default  to using port 1080 for

       The proxy string may be prefixed with [scheme]:// to specify which kind of proxy is used.

                     HTTP Proxy. Default when no scheme or proxy type is specified.

                     HTTPS Proxy. (Added in 7.52.0 for OpenSSL, GnuTLS and NSS)

                     SOCKS4 Proxy.

                     SOCKS4a Proxy. Proxy resolves URL hostname.

                     SOCKS5 Proxy.

                     SOCKS5 Proxy. Proxy resolves URL hostname.

       Without a scheme prefix, CURLOPT_PROXYTYPE(3) can be used to specify which kind  of  proxy
       the string identifies.

       When  you  tell  the  library  to  use  a  HTTP  proxy, libcurl will transparently convert
       operations to HTTP even if you specify an FTP URL etc. This may have  an  impact  on  what
       other  features  of  the  library  you  can  use, such as CURLOPT_QUOTE(3) and similar FTP
       specifics that don't work unless you tunnel through the  HTTP  proxy.  Such  tunneling  is
       activated with CURLOPT_HTTPPROXYTUNNEL(3).

       Setting  the  proxy  string  to  "" (an empty string) will explicitly disable the use of a
       proxy, even if there is an environment variable set for it.

       A proxy host string can also  include  protocol  scheme  (http://)  and  embedded  user  +

       The application does not have to keep the string around after setting this option.

Environment variables

       libcurl  respects  the proxy environment variables named http_proxy, ftp_proxy, sftp_proxy
       etc. If set, libcurl will use the specified proxy for that URL scheme. So for  a  "FTP://"
       URL, the ftp_proxy is considered. all_proxy is used if no protocol specific proxy was set.

       If  no_proxy  (or NO_PROXY) is set, it can specify a list of host names to not use a proxy
       for (even if one of the previous mention variables are set). That is the exact  equivalent
       of setting the CURLOPT_NOPROXY(3) option.

       The CURLOPT_PROXY(3) and CURLOPT_NOPROXY(3) options override environment variables.


       Default is NULL, meaning no proxy is used.

       When  you  set  a  host name to use, do not assume that there's any particular single port
       number used widely for proxies. Specify it!


       All except file://. Note that some protocols don't do very well over proxy.


       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "");
         curl_easy_setopt(curl, CURLOPT_PROXY, "http://proxy:80");


       Since 7.14.1 the proxy environment variable names can include the protocol scheme.

       Since 7.21.7 the proxy string supports the socks protocols as "schemes".

       Since 7.50.2, unsupported schemes in proxy strings cause libcurl to return error.


       Returns  CURLE_OK  if   proxies   are   supported,   CURLE_UNKNOWN_OPTION   if   not,   or
       CURLE_OUT_OF_MEMORY if there was insufficient heap space.