Ubuntu Manpage: CURLOPT_PRE_PROXY - pre-proxy host to use

name
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default
protocols
example
availability
return value
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Provided by: libcurl4-doc_8.12.1-2ubuntu1_all

NAME

       CURLOPT_PRE_PROXY - pre-proxy host 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 null-terminated
string holding the hostname 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 defaults 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(3) 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) explicitly disables the use of a pre proxy.

When you set a hostname to use, do not assume that there is any particular single port number used widely
for proxies. Specify it.

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

Using this option multiple times makes the last set string override the previous ones. Set it to NULL to
disable its use again.

DEFAULT

       NULL

PROTOCOLS

       This functionality affects all supported protocols

EXAMPLE

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

AVAILABILITY

       Added in curl 7.52.0

RETURN VALUE

       curl_easy_setopt(3) returns a CURLcode indicating success or error.

       CURLE_OK (0) means everything was OK, non-zero means an error occurred, see libcurl-errors(3).