About

The goal of this package is to imitate tail -F | grep functionality in node.

This is the simplest way to tail a file, filter the output, and run a function. The program will continue to tail the file until the process is killed. It will also continue to tail the file even if the file is deleted and recreated.

Basic Usage

The below code will tail the file /var/log/my-app.log and print the contents of each change to the console.

const Tail = require('tailf-grep');
const fn = changes => { console.log(changes); };
const tail = new Tail('/var/log/my-app.log', fn);

Advanced Usage

The below code will tail the file /var/log/my-app.log and print the contents of each change to the console provided that the change contains a string in the array.

const Tail = require('tailf-grep');
const fn = changes => { console.error(changes); };
const tail = new Tail('/var/log/my-app.log', ['ERROR', 'WARNING'], fn);

Excluding Text

You can also tell the tailer to ignore certain text in another array. The below code will tail the file /var/log/my-app.log and print the contents of each change to the console provided that the change does not contain a string in the array.

const Tail = require('tailf-grep');
const fn = changes => { console.error(changes); };
const tail = new Tail('/var/log/my-app.log', ['ERROR', 'WARNING'], ['exclude me', 'definitely don\'t report me'], fn);