curl/docs/libcurl/opts/CURLOPT_PRE_PROXY.3

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.TH CURLOPT_PRE_PROXY 3 "16 Nov 2016" "libcurl 7.52.0" "curl_easy_setopt options"
.SH NAME
CURLOPT_PRE_PROXY \- pre-proxy host to use
.SH SYNOPSIS
.nf
#include <curl/curl.h>

CURLcode curl_easy_setopt(CURL *handle, CURLOPT_PRE_PROXY, char *preproxy);
.fi
.SH DESCRIPTION
Set the \fIpreproxy\fP to use for the upcoming request. The parameter
should be a char * to a null-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 \fICURLOPT_PROXYPORT(3)\fP. 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 \fICURLOPT_PROXY\fP 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
\fICURLPROXY_SOCKS5_HOSTNAME\fP 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.
.SH 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!
.SH PROTOCOLS
All except file://. Note that some protocols do not work well over proxy.
.SH EXAMPLE
.nf
CURL *curl = curl_easy_init();
if(curl) {
  curl_easy_setopt(curl, CURLOPT_URL, "https://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);
}
.fi
.SH AVAILABILITY
Added in 7.52.0
.SH 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.
.SH "SEE ALSO"
.BR CURLOPT_PROXY "(3), " CURLOPT_HTTPPROXYTUNNEL "(3), "