tail a file in node
npm install tailThe zero dependency Node.js module for tailing a file
!npm
Made with ❤️ by Luca Grulla
1. TOC
{:toc}
``bash`
npm install tail
`javascript
Tail = require('tail').Tail;
tail = new Tail("fileToTail");
tail.on("line", function(data) {
console.log(data);
});
tail.on("error", function(error) {
console.log('ERROR: ', error);
});
`
If you want to stop tail:
`javascript`
tail.unwatch()
To start watching again:
`javascript`
tail.watch()
The only mandatory parameter is the path to the file to tail.
`javascript`
var fileToTail = "/path/to/fileToTail.txt";
new Tail(fileToTail)
If the file is missing or invalid `Tail` constructor will throw an Exception and won't initialize.
`javascript`
try {
new Tail('missingFile.txt')
} catch (ex) {
console.log(ex)
}
Optional parameters can be passed via a hash:
`javascript`
var options= {separator: /[\r]{0,1}\n/, fromBeginning: false, fsWatchOptions: {}, follow: true, logger: console}
new Tail(fileToTail, options)
* separator: the line separator token (default: /[\r]{0,1}\n/ to handle linux/mac (9+)/windows). Pass null for is binary files with no line separator.fsWatchOptions
* : the full set of options that can be passed to fs.watch as per node documentation (default: {}).fromBeginning
* : tail from the beginning of the file (default: false). If fromBeginning is true nLines will be ignored.follow
* : simulate tail -F option. In the case the file is moved/renamed/logrotated, if set to true will start tailing again after a 1 second delay; if set to false it will emit an error event (default: true).logger
* : a logger object(default: no logger). The passed logger should follow the folliwing signature:info([data][, ...])
*
*
* : tail from the last n lines. (default: undefined). Ignored if fromBeginning is set to true. useWatchFile
* : if set to true will force the use of fs.watchFile over delegating to the library the choice between fs.watch and fs.watchFile (default: false).encoding
* : the file encoding (default:utf-8).flushAtEOF
* : set to true to force flush of content when end of file is reached. Useful when there's no separator character at the end of the file (default: false).
Tail emits two events:
* line
`javascript`
tail.on('line', (data) => {
console.log(data)
})
* error
`javascript``
tail.on('error', (err) => {
console.log(err)
})
The error emitted is either the underline exception or a descriptive string.
Tail was born as part of a data firehose. Read more about that project here.
Tail originally was written in CoffeeScript. Since December 2020 it's pure ES6.
MIT. Please see License file for more details.