# proxy-from-env
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[](https://travis-ci.org/Rob--W/proxy-from-env)
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[](https://coveralls.io/github/Rob--W/proxy-from-env?branch=master)
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`proxy-from-env` is a Node.js package that exports a function (`getProxyForUrl`)
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that takes an input URL (a string or
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[`url.parse`](https://nodejs.org/docs/latest/api/url.html#url_url_parsing)'s
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return value) and returns the desired proxy URL (also a string) based on
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standard proxy environment variables. If no proxy is set, an empty string is
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returned.
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It is your responsibility to actually proxy the request using the given URL.
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Installation:
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```sh
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npm install proxy-from-env
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```
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## Example
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This example shows how the data for a URL can be fetched via the
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[`http` module](https://nodejs.org/api/http.html), in a proxy-aware way.
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```javascript
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var http = require('http');
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var parseUrl = require('url').parse;
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var getProxyForUrl = require('proxy-from-env').getProxyForUrl;
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var some_url = 'http://example.com/something';
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// // Example, if there is a proxy server at 10.0.0.1:1234, then setting the
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// // http_proxy environment variable causes the request to go through a proxy.
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// process.env.http_proxy = 'http://10.0.0.1:1234';
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//
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// // But if the host to be proxied is listed in NO_PROXY, then the request is
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// // not proxied (but a direct request is made).
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// process.env.no_proxy = 'example.com';
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var proxy_url = getProxyForUrl(some_url); // <-- Our magic.
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if (proxy_url) {
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// Should be proxied through proxy_url.
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var parsed_some_url = parseUrl(some_url);
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var parsed_proxy_url = parseUrl(proxy_url);
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// A HTTP proxy is quite simple. It is similar to a normal request, except the
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// path is an absolute URL, and the proxied URL's host is put in the header
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// instead of the server's actual host.
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httpOptions = {
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protocol: parsed_proxy_url.protocol,
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hostname: parsed_proxy_url.hostname,
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port: parsed_proxy_url.port,
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path: parsed_some_url.href,
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headers: {
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Host: parsed_some_url.host, // = host name + optional port.
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},
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};
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} else {
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// Direct request.
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httpOptions = some_url;
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}
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http.get(httpOptions, function(res) {
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var responses = [];
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res.on('data', function(chunk) { responses.push(chunk); });
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res.on('end', function() { console.log(responses.join('')); });
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});
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```
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## Environment variables
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The environment variables can be specified in lowercase or uppercase, with the
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lowercase name having precedence over the uppercase variant. A variable that is
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not set has the same meaning as a variable that is set but has no value.
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### NO\_PROXY
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`NO_PROXY` is a list of host names (optionally with a port). If the input URL
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matches any of the entries in `NO_PROXY`, then the input URL should be fetched
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by a direct request (i.e. without a proxy).
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Matching follows the following rules:
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- `NO_PROXY=*` disables all proxies.
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- Space and commas may be used to separate the entries in the `NO_PROXY` list.
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- If `NO_PROXY` does not contain any entries, then proxies are never disabled.
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- If a port is added after the host name, then the ports must match. If the URL
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does not have an explicit port name, the protocol's default port is used.
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- Generally, the proxy is only disabled if the host name is an exact match for
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an entry in the `NO_PROXY` list. The only exceptions are entries that start
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with a dot or with a wildcard; then the proxy is disabled if the host name
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ends with the entry.
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See `test.js` for examples of what should match and what does not.
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### \*\_PROXY
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The environment variable used for the proxy depends on the protocol of the URL.
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For example, `https://example.com` uses the "https" protocol, and therefore the
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proxy to be used is `HTTPS_PROXY` (_NOT_ `HTTP_PROXY`, which is _only_ used for
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http:-URLs).
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The library is not limited to http(s), other schemes such as
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`FTP_PROXY` (ftp:),
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`WSS_PROXY` (wss:),
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`WS_PROXY` (ws:)
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are also supported.
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If present, `ALL_PROXY` is used as fallback if there is no other match.
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## External resources
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The exact way of parsing the environment variables is not codified in any
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standard. This library is designed to be compatible with formats as expected by
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existing software.
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The following resources were used to determine the desired behavior:
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- cURL:
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https://curl.haxx.se/docs/manpage.html#ENVIRONMENT
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https://github.com/curl/curl/blob/4af40b3646d3b09f68e419f7ca866ff395d1f897/lib/url.c#L4446-L4514
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https://github.com/curl/curl/blob/4af40b3646d3b09f68e419f7ca866ff395d1f897/lib/url.c#L4608-L4638
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- wget:
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https://www.gnu.org/software/wget/manual/wget.html#Proxies
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http://git.savannah.gnu.org/cgit/wget.git/tree/src/init.c?id=636a5f9a1c508aa39e35a3a8e9e54520a284d93d#n383
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http://git.savannah.gnu.org/cgit/wget.git/tree/src/retr.c?id=93c1517c4071c4288ba5a4b038e7634e4c6b5482#n1278
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- W3:
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https://www.w3.org/Daemon/User/Proxies/ProxyClients.html
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- Python's urllib:
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https://github.com/python/cpython/blob/936135bb97fe04223aa30ca6e98eac8f3ed6b349/Lib/urllib/request.py#L755-L782
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https://github.com/python/cpython/blob/936135bb97fe04223aa30ca6e98eac8f3ed6b349/Lib/urllib/request.py#L2444-L2479
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