solution without using wc:

var i;

var count = 0;

require('fs').createReadStream(process.argv[2])

  .on('data', function(chunk) {

    for (i=0; i < chunk.length; ++i)

      if (chunk[i] == 10) count++;

  })

  .on('end', function() {

    console.log(count);

  });

it's slower, but not that much you might expect - 0.6s for 140M+ file including node.js loading & startup time

>time node countlines.js video.mp4 

619643



real    0m0.614s

user    0m0.489s

sys 0m0.132s



>time wc -l video.mp4 

619643 video.mp4

real    0m0.133s

user    0m0.108s

sys 0m0.024s



>wc -c video.mp4

144681406  video.mp4