javascript - Node.js monitor file for changes and parse them

Question

I need to monitor a file for changes. Due to a large amount of new entries to this file I would need to 'monitor' this file. I would need to get the new inserted content to this file to be able to parse this content.

I found this code:

fs.watchFile('var/log/query.log', function() {
console.log('File Changed ...');
//how to get the new line which is now inserted?
});

Answer 1

On bash you would do something like that with tail --follow.

There is also a package tail availible. you can watch on a file, and get new lines with an event:

const Tail = require('tail').Tail;
var tail = new Tail("var/log/query.log");
tail.watch()
tail.on("line", data => {
  console.log(data);
});