ls-head-tail

var through = require("through");
var split = require("split");
var fs = require("fs");
var util = require("util");
var combine = require("stream-combiner");
var Readable = require("stream").Readable;

function MyReadable(dir) {
    this._queue = [dir];
    Readable.call(this);
}

util.inherits(MyReadable, Readable);

MyReadable.prototype._read = function () {

    var self = this;
    var queue = this._queue;

    if (!queue.length) {
        push(null);
        return;
    }

    function push(data) {
        self.push(data);
    }

    var dir = queue.shift();

    fs.readdir(dir, function (err, list) {
        if (err) self.emit("error", err);
        push(list.toString().split(",").join("\n"));
    });
};

function head(amount) {
    amount = Math.abs(amount);
    var counter = 0;
    return combine(split("\n"), through(function (line) {
        if (++counter > amount) this.queue(null);
        if (counter > 1)
            this.queue("\n");
        this.queue(line);
    }));
}

function tail(lines) {
    lines = Math.abs(lines);
    var buffer = [];
    return combine(split("\n"), through(function (line) {
        buffer.push(line);
    }, function () {
        buffer = buffer.slice(-lines);
        while (buffer.length) {
            this.queue(buffer.shift());
            this.queue("\n");
        }
        this.queue(null);
    }));
}


new MyReadable(__dirname)
    .pipe(head(5))
    .pipe(tail(3))
    .pipe(process.stdout);