tailcat

A Node.js file watcher like tail +0f

Install

$ npm install tailcat --save

Key properties

• Can watch non-existing files that still need to be created
• Can handle file deletion/removal
• 0 external dependencies
• Excellent test coverage
• Can handle fast updating files

Usage

import {TailCat} from 'tailcat'

const tailCat = new TailCat('./source/foo.txt'); // Configures the file that is watched

await tailcat.watch(); // Starts watching the file

tailcat.on('data', data => { // Event handler, will emit each line of the watched file
	//...
});

const cursor = await tailCat.unwatch(); // Stops watching the file and returns the current cursor

// ... some time passes

await tailCat.watch({cursor}); // Starts watching again from the cursor. Will eagerly read the data written during the pause if the cursor is lower then the file size.

API

TailCat(path)

Constructor for a tailcat instance

path

Type: String Description: Path to the file. The file itself needs to be newline delimited (CSV, NDJSON, etc...). Binary files are not supported.

watch([options]): Promise<undefined>

Starts watching a file.

options.cursor

Type: number Optional: true Description: The cursor from there to start watching. If no cursor is provided, it will continue reading from the cursor that has stored internally in the TailCat instance. If no read operations have been performed yet, it will start from position 0.

unwatch(): Promise<number>

Stops watching a file and returns the current cursor position.

on('data', (data: string) => {...})

Emits events when a line has been processed from the watched file

Contributions

I welcome any contributions.

Author

• Simon Jang