Tribblix: manual page: CURLOPT

CURLOPT_PROXY(3) Introduction to Library Functions CURLOPT_PROXY(3)

NAME

CURLOPT_PROXY - proxy to use

SYNOPSIS

#include <curl/curl.h>

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

DESCRIPTION

Set the proxy to use for transfers with this easy handle. 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 (but
discouraged) be specified with the separate option
CURLOPT_PROXYPORT(3). If not specified, libcurl defaults to using
port 1080 for proxies.

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

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

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

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

https://
HTTPS Proxy. (Added in 7.52.0 for OpenSSL and GnuTLS Since
7.87.0, it also works for BearSSL, mbedTLS, Rustls, Schannel,
Secure Transport and wolfSSL.)

This uses HTTP/1 by default. Setting CURLOPT_PROXYTYPE(3) to
CURLPROXY_HTTPS2 allows libcurl to negotiate using HTTP/2 with
proxy.

socks4://
SOCKS4 Proxy.

socks4a://
SOCKS4a Proxy. Proxy resolves URL hostname.

socks5://
SOCKS5 Proxy.

socks5h://
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 an HTTP proxy, libcurl transparently
converts 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 do not work
unless you tunnel through the HTTP proxy. Such tunneling is activated
with CURLOPT_HTTPPROXYTUNNEL(3).

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

Unix domain sockets are supported for socks proxies since 7.84.0. Set
localhost for the host part. e.g.
socks5h://localhost/path/to/socket.sock

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

When a proxy is used, the active FTP mode as set with
CUROPT_FTPPORT(3), cannot be used.

Doing FTP over an HTTP proxy without CURLOPT_HTTPPROXYTUNNEL(3) set
makes libcurl do HTTP with an FTP URL over the proxy. For such
transfers, common FTP specific options do not work, for example
CURLOPT_USE_SSL(3).

Authentication
The proxy can also be specified with its associated credentials like
for ordinary URLs in the style: scheme://username:password@hostname

Alternatively, set them using CURLOPT_PROXYUSERNAME(3) and
CURLOPT_PROXYPASSWORD(3).

Environment variables
libcurl respects the proxy environment variables named http_proxy,
ftp_proxy, sftp_proxy etc. If set, libcurl uses the specified proxy
for that URL scheme. For an "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 is the exact equivalent of
setting the CURLOPT_NOPROXY(3) option.

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

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_PROXY, "http://proxy:80");
curl_easy_perform(curl);
}
}

HISTORY

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.

AVAILABILITY

Added in curl 7.1

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).