Provided by: libcurl4-doc_7.55.1-1ubuntu2_all bug

NAME

       CURLOPT_PRE_PROXY - set pre-proxy to use

SYNOPSIS

       #include <curl/curl.h>

       CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PRE_PROXY, char *preproxy);

DESCRIPTION

       Set  the  preproxy  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
       proxies.

       A pre proxy is a SOCKS proxy that curl connects to before it connects to the HTTP(S) proxy
       specified in the CURLOPT_PROXY option. The pre proxy can only be a SOCKS proxy.

       The pre proxy string should be prefixed with [scheme]:// to specify which kind of socks is
       used. Use socks4://, socks4a://, socks5:// or socks5h:// (the last one  to  enable  socks5
       and asking the proxy to do the resolving, also known as CURLPROXY_SOCKS5_HOSTNAME type) to
       request the specific SOCKS version to be used. Otherwise SOCKS4 is used as default.

       Setting the pre proxy string to "" (an empty string) will explicitly disable the use of  a
       pre proxy.

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

DEFAULT

       Default is NULL, meaning no pre 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!

PROTOCOLS

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

EXAMPLE

       CURL *curl = curl_easy_init();
       if(curl) {
         curl_easy_setopt(curl, CURLOPT_URL, "http://example.com/file.txt");
         curl_easy_setopt(curl, CURLOPT_PREPROXY, "socks4://socks-proxy:1080");
         curl_easy_setopt(curl, CURLOPT_PROXY, "http://proxy:80");
         curl_easy_perform(curl);
       }

AVAILABILITY

       Added in 7.52.0

RETURN VALUE

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

SEE ALSO

       CURLOPT_PROXY(3), CURLOPT_HTTPPROXYTUNNEL(3),