Read previous/next line of text file with fs?

Question

I was wondering if it was at all possible to read the very last line of a text file. And then, read the one before that. I can see all the data in the console , but I have no idea how to just display one line.

Currently, I am using fs and byline , to write and read files, respectively.

Answer 1

Use the readline core module instead of byline , and keep track of the current and previous lines when you receive events.

var rl = require('readline').createInterface({
  input: require('fs').createReadStream('input.file')
});

var current = "";
var prev = "";

rl.on('line', function (line) {
  prev = current;
  current = line;
});

rl.on('close', function () {
  console.log('Last line:', current);
  console.log('Prev line:', prev);
});

Alternatively, just read the whole file into a string and then split it after line breaks.