How to do `tail -f logfile.txt`-like processing in node.js?

Question

tail -f logfile.txt outputs the last 10 lines of logfile.txt, and then continues to output appended data as the file grows.

What\'s the recommended way

Answer 1

you can try to use fs.read instead of ReadStream

var fs = require('fs')

var buf = new Buffer(16);
buf.fill(0);
function read(fd)
{
    fs.read(fd, buf, 0, buf.length, null, function(err, bytesRead, buf1) {
        console.log(buf1.toString());
        if (bytesRead != 0) {
            read(fd);
        } else {
            setTimeout(function() {
                read(fd);
            }, 1000);
        }
    }); 
}

fs.open('logfile', 'r', function(err, fd) {
    read(fd);
});

Note that read calls callback even if there is no data and it just reached end of file. Without timeout you'll get 100% cpu here. You could try to use fs.watchFile to get new data immediately.