@smpx/tail

Watch and tail a file in nodejs tail -f -n     🎉 No Dependencies

Install

npm install @smpx/tail

Or with yarn:

yarn add @smpx/tail

Use

const tail = require('@smpx/tail');

const stream = tail('/var/log/syslog', {
    numLines: 20,
    watch: true,
});

stream.on('line', (line) => {
    console.log(line);
});

stream.on('error', (err) => {
    console.error(err);
});

If you want to stop watching:

stream.close();

API

tail(filename, options)

• filename: Path of the file to tail
• options:
  • bufferSize: Use this bufferSize when reading from the file (default 2048)
  • encoding: Encoding of the file (default utf8)
  • numLines: Number of lines to read initially (default 10) (similar to tail -n)
  • watch: Whether to watch the file for changes (default false) (similar to tail -f)
    • Setting this to true will keep the process alive until you call close
  • filter: An optional function to emit only those lines which pass the criteria

    const stream = tail('/var/log/syslog', {
        numLines: 20,
        watch: true,
        filter: (line) => {
            if (!line) return false;
            return JSON.parse(line).level === 'error';
        }
    });

Returns:

An eventemitter, with two events, line and error and a function close.

• on('line', (line) => {}): emitted whenever we read a new line from the file
• on('error', (err) => {}): emitted whenever there's an error
• close: a method to close and unwatch the file

LICENSE

MIT