CODEWITHSUNDEEP
javascriptnode.jsfilesplit
Teleporting Goat
Teleporting Goat

Reputation: 467

Read from file and find specific lines

I need to fetch information in settings a file (I can't change the format) according to certain keywords. The file goes like this:

username=myusername
address=156a1355e3486f4
data=function(i){if (i!=0) return true; else return false;}

The system is <key> = <value> \n. There can be =, spaces or other characters in the value part, but never line breaks. Keys are unique (in the "key part", they can appear in values, but \nkey= appears only once in the file for every key).

With a shell script, I find my values like this: 

username=`grep ^username file.txt | sed "s/^username=//"`

Grep will return username=someusername and sed replaces the key and = with nothing, leaving only the value.

In node.js, I would like to access some of the data in the file. For example, I want the value for address and data.

How could I do this in node.js ? After fs.readFile(file.txt) I don't know what to do. I guess I will have to use split, but using \n doesn't seem to be the best option, maybe regex can help ?

The ideal thing would be to "find a substring starting with \nkey= and ending with the first \n", then I could easily split to find the value.

Upvotes: 2

Views: 5545

Answers (2)

MatthieuLemoine
MatthieuLemoine

Reputation: 706

Using split and reduce, you can do something like that : 

fs.readFile('file.txt', { encoding : 'utf8' }, data => {
  const settings = data
    .split('\n')
    .reduce((obj, line) => {
      const splits = line.split('=');
      const key = splits[0];
      if (splits.length > 1) {
        obj[key] = splits.slice(1).join('=');
      }
      return obj;
    }, {});
  // ...
});

Your settings will be stored as key/value in the settings object.

Upvotes: 0

ibrahim mahrir
ibrahim mahrir

Reputation: 31712

// @text is the text read from the file.
// @key is the key to find its value
function getValueByKey(text, key){
    var regex = new RegExp("^" + key + "=(.*)$", "m");
    var match = regex.exec(text);
    if(match)
        return match[1];
    else
        return null;
}

EXAMPLE:

// text should be obtained using fs.readFile...
var text = "username=myusername\naddress=156a1355e3486f4\ndata=function(i){if (i!=0) return true; else return false;}";


function getValueByKey(text, key){
    var regex = new RegExp("^" + key + "=(.*)$", "m");
    var match = regex.exec(text);
    if(match)
        return match[1];
    else
        return null;
}

console.log("adress: ", getValueByKey(text, "address"));
console.log("username: ", getValueByKey(text, "username"));
console.log("foo (non exist): ", getValueByKey(text, "foo"));

Upvotes: 5

Related Questions