The zero dependency Node.js module for tailing a file
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The zero dependency Node.js module for tailing a file


license npm npm

Author: Luca Grulla -


npm install tail


Tail = require('tail').Tail;

tail = new Tail("fileToTail");

tail.on("line", function(data) {

tail.on("error", function(error) {
  console.log('ERROR: ', error);

If you want to stop tail:


To start watching again:


The only mandatory parameter is the path to the file to tail.

var fileToTail = "/path/to/fileToTail.txt";
new Tail(fileToTail)

Optional parameters can be passed via a hash:

var options= {separator: /[\r]{0,1}\n/, fromBeginning: false, fsWatchOptions: {}, follow: true, logger: console}
new Tail(fileToTail, options)

Constructor parameters

  • separator: the line separator token (default: /[\r]{0,1}\n/ to handle linux/mac (9+)/windows). Pass null if your file is binary there's no line separator.
  • fsWatchOptions: the full set of options that can be passed to as per node documentation (default: {}).
  • fromBeginning: forces the tail of the file from the very beginning of it instead of from the first new line that will be appended (default: false).
  • follow: simulate tail -F option. In the case the file is moved/renamed (or logrotated), if set to true tail will try to start tailing again after a 1 second delay, if set to false it will just emit an error event (default: true).
  • logger: a logger object(default: no logger). The passed logger has to respond to two methods:
    • info([data][, ...])
    • error([data][, ...])
  • useWatchFile: if set to true will force the use of fs.watchFile rather than delegating to the library the choice between and fs.watchFile (default: false).
  • encoding: the encoding of the file to tail (default:utf-8).
  • flushAtEOF: set to true if you want to force flush of content when end of file is reached. Particularly useful when there's no separator character at the end of the file (default: false).

Emitted events

Tail emits two events:

  • line
  • error

How to contribute

Tail is written in CoffeeScript.

The Cakefile generates the javascript that is then published to npm.


Tail was born as part of a data firehose. Read about it here.


MIT. Please see License file for more details.