Reading environment variables from file with node.js

Question

I have a number of bash/shell variables in a file, I would like to read them into a node.js script (or javascript I guess) to eval them and set javascript variables.

e.g. the file contains:

gateway_ip=192.168.1.1

mask=255.255.255.0

port=8080

I've tried the following:

function readConfigFile() {
 var filename="/home/pi/.data-test";
 fs.readFile(filename, 'utf8', function(err, data) {
 var lines = data.split('\n');
 for(var i = 0; i < lines.length-1; i++) {
 console.log(lines[i]);
 eval(lines[i]);
 console.log(gateway_ip);
 }
 });
}

and it spits out the lines as text, but I doesn't seem to be able to make the javascript variable. The error is:

undefined:1 default_gateway=192.168.1.1

Is there something obvious I've missed here?

• Rudolf Manusachi: you can write config in JSON file, and simply require as Object

Answer 1

What you're doing here is eval('gateway_ip=192.168.1.1').

192.168.1.1 is not valid javascript. It should have quotation marks. Try this instead:

 var lines = data.split('\n');
 var options = {};
 for(var i = 0; i < lines.length-1; i++) {
 var parts = lines[i].split('=');
 options[parts[0].trim()] = parts.slice(1).join('=').trim();
 }
 // You now have everything in options. 

You can use global instead of options to set those variables on the global scope.

• dandavis: good answer. 2 minor suggestions: 1. trim() the line and both sides. 2. replace parts[1] with parts.slice(1).join("=") to not throw away parts of a value with an = in it
• AEngineer: Thanks, I will use this. (I was hoping there was a simple one-liner though).

Answer 2

This is not very JavaScript-ish. An easier way to do it is to use JSON for your config file. For example, use this config.json:

{
 "gateway_ip": "192.168.1.1",
 "mask": "255.255.255.0",
 "port": "8080"
}

Then you can simply require it:

var config = require('./config.json');
console.log(config);

An additional bonus is that this will also catch formatting errors in the JSON file.

• AEngineer: Thanks, yes I know, the reason it is done like this is because it is used to configure the network settings on a Raspberry Pi upon boot. The options are presented as defaults as last used.