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?

you can write config in JSON file, and simply require as Object — Rudolf Manusachi
– Rudolf Manusachi, Commented Dec 19, 2015 at 23:22

Louay Alakkad · Accepted Answer · 2015-12-20 09:35:42Z

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.

edited Dec 20, 2015 at 9:35

answered Dec 19, 2015 at 23:19

Louay Alakkad

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2 Comments

dandavis Over a year ago

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 Over a year ago

Thanks, I will use this. (I was hoping there was a simple one-liner though).

Joost Vunderink · Accepted Answer · 2015-12-20 08:35:16Z

1

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.

answered Dec 20, 2015 at 8:35

Joost Vunderink

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1 Comment

AEngineer Over a year ago

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.

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