# proxy-from-env

[![Build Status](https://travis-ci.org/Rob--W/proxy-from-env.svg?branch=master)](https://travis-ci.org/Rob--W/proxy-from-env) [![Coverage Status](https://coveralls.io/repos/github/Rob--W/proxy-from-env/badge.svg?branch=master)](https://coveralls.io/github/Rob--W/proxy-from-env?branch=master)

`proxy-from-env` is a Node.js package that exports a function (`getProxyForUrl`) that takes an input URL (a string or [`url.parse`](https://nodejs.org/docs/latest/api/url.html#url_url_parsing)'s return value) and returns the desired proxy URL (also a string) based on standard proxy environment variables. If no proxy is set, an empty string is returned.

It is your responsibility to actually proxy the request using the given URL.

Installation:

```sh
npm install proxy-from-env
```

## Example

This example shows how the data for a URL can be fetched via the [`http` module](https://nodejs.org/api/http.html), in a proxy-aware way.

```javascript
var http = require('http');
var parseUrl = require('url').parse;
var getProxyForUrl = require('proxy-from-env').getProxyForUrl;

var some_url = 'http://example.com/something';

// // Example, if there is a proxy server at 10.0.0.1:1234, then setting the
// // http_proxy environment variable causes the request to go through a proxy.
// process.env.http_proxy = 'http://10.0.0.1:1234';
// 
// // But if the host to be proxied is listed in NO_PROXY, then the request is
// // not proxied (but a direct request is made).
// process.env.no_proxy = 'example.com';

var proxy_url = getProxyForUrl(some_url);  // <-- Our magic.
if (proxy_url) {
  // Should be proxied through proxy_url.
  var parsed_some_url = parseUrl(some_url);
  var parsed_proxy_url = parseUrl(proxy_url);
  // A HTTP proxy is quite simple. It is similar to a normal request, except the
  // path is an absolute URL, and the proxied URL's host is put in the header
  // instead of the server's actual host.
  httpOptions = {
    protocol: parsed_proxy_url.protocol,
    hostname: parsed_proxy_url.hostname,
    port: parsed_proxy_url.port,
    path: parsed_some_url.href,
    headers: {
      Host: parsed_some_url.host,  // = host name + optional port.
    },
  };
} else {
  // Direct request.
  httpOptions = some_url;
}
http.get(httpOptions, function(res) {
  var responses = [];
  res.on('data', function(chunk) { responses.push(chunk); });
  res.on('end', function() { console.log(responses.join(''));  });
});

```

## Environment variables

The environment variables can be specified in lowercase or uppercase, with the lowercase name having precedence over the uppercase variant. A variable that is not set has the same meaning as a variable that is set but has no value.

### NO\_PROXY

`NO_PROXY` is a list of host names (optionally with a port). If the input URL matches any of the entries in `NO_PROXY`, then the input URL should be fetched by a direct request (i.e. without a proxy).

Matching follows the following rules:

* `NO_PROXY=*` disables all proxies.
* Space and commas may be used to separate the entries in the `NO_PROXY` list.
* If `NO_PROXY` does not contain any entries, then proxies are never disabled.
* If a port is added after the host name, then the ports must match. If the URL does not have an explicit port name, the protocol's default port is used.
* Generally, the proxy is only disabled if the host name is an exact match for an entry in the `NO_PROXY` list. The only exceptions are entries that start with a dot or with a wildcard; then the proxy is disabled if the host name ends with the entry.

See `test.js` for examples of what should match and what does not.

### \*\_PROXY

The environment variable used for the proxy depends on the protocol of the URL. For example, `https://example.com` uses the "https" protocol, and therefore the proxy to be used is `HTTPS_PROXY` (*NOT* `HTTP_PROXY`, which is *only* used for http:-URLs).

The library is not limited to http(s), other schemes such as `FTP_PROXY` (ftp:), `WSS_PROXY` (wss:), `WS_PROXY` (ws:) are also supported.

If present, `ALL_PROXY` is used as fallback if there is no other match.

## External resources

The exact way of parsing the environment variables is not codified in any standard. This library is designed to be compatible with formats as expected by existing software. The following resources were used to determine the desired behavior:

* cURL: <https://curl.haxx.se/docs/manpage.html#ENVIRONMENT\\>
  <https://github.com/curl/curl/blob/4af40b3646d3b09f68e419f7ca866ff395d1f897/lib/url.c#L4446-L4514\\>
  <https://github.com/curl/curl/blob/4af40b3646d3b09f68e419f7ca866ff395d1f897/lib/url.c#L4608-L4638>
* wget: <https://www.gnu.org/software/wget/manual/wget.html#Proxies\\>
  <http://git.savannah.gnu.org/cgit/wget.git/tree/src/init.c?id=636a5f9a1c508aa39e35a3a8e9e54520a284d93d#n383\\>
  <http://git.savannah.gnu.org/cgit/wget.git/tree/src/retr.c?id=93c1517c4071c4288ba5a4b038e7634e4c6b5482#n1278>
* W3: <https://www.w3.org/Daemon/User/Proxies/ProxyClients.html>
* Python's urllib: <https://github.com/python/cpython/blob/936135bb97fe04223aa30ca6e98eac8f3ed6b349/Lib/urllib/request.py#L755-L782\\>
  <https://github.com/python/cpython/blob/936135bb97fe04223aa30ca6e98eac8f3ed6b349/Lib/urllib/request.py#L2444-L2479>


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://civictech-ou.gitbook.io/nova-docs/use-cases/node_modules/proxy-from-env.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.