egSpawn.js

#!/usr/bin/gjs

/*
GJS example showing how to build Gtk javascript applications
executing a non blocking command line call, it uses
TextBuffer, TextView, GLib.spawn_async_with_pipes,
Gio.UnixInputStream, Gio.DataInputStream and read_line_async

Run it with:
    gjs egSpawn.js
*/

const Gio   = imports.gi.Gio;
const GLib  = imports.gi.GLib;
const Gtk   = imports.gi.Gtk;
const Lang  = imports.lang;

// Get application folder and add it into the imports path
function getAppFileInfo() {
    let stack = (new Error()).stack,
        stackLine = stack.split('\n')[1],
        coincidence, path, file;

    if (!stackLine) throw new Error('Could not find current file (1)');

    coincidence = new RegExp('@(.+):\\d+').exec(stackLine);
    if (!coincidence) throw new Error('Could not find current file (2)');

    path = coincidence[1];
    file = Gio.File.new_for_path(path);
    return [file.get_path(), file.get_parent().get_path(), file.get_basename()];
}
const path = getAppFileInfo()[1];
imports.searchPath.push(path);

// Import spawn library
const Spawn = imports.assets.spawn;

const App = function () { 

    this.title = 'Example Spawn';
    GLib.set_prgname(this.title);
};


App.prototype.run = function (ARGV) {

    this.application = new Gtk.Application();
    this.application.connect('activate', () => { this.onActivate(); });
    this.application.connect('startup', () => { this.onStartup(); });
    this.application.run([]);
};

App.prototype.onActivate = function () {

    this.window.show_all();
};

App.prototype.onStartup = function() {

    this.buildUI();
    this.spawn();
};

App.prototype.buildUI = function() {

    let scroll;

    this.window = new Gtk.ApplicationWindow({ application: this.application,
                                              title: this.title,
                                              default_height: 200,
                                              default_width: 200,
                                              window_position: Gtk.WindowPosition.CENTER });
    try {
        this.window.set_icon_from_file(path + '/assets/appIcon.png');
    } catch (err) {
        this.window.set_icon_name('application-x-executable');
    }

    scroll = new Gtk.ScrolledWindow({ vexpand: true });
    this.buffer = new Gtk.TextBuffer();
    this.buffer.insert_at_cursor('Result:\n', -1);
    this.view = new Gtk.TextView();
    this.view.set_buffer(this.buffer);

    scroll.add(this.view);
    this.window.add(scroll);
};

App.prototype.spawn = function() {

    let reader;

    reader = new Spawn.SpawnReader();
    reader.spawn('./', ['ls', '-ltr', '.'], (line) => {
        this.buffer.insert_at_cursor(String(line) + '\n', -1);
    });

/*  // Example of 'continuous' read with 'tail':
    reader.spawn('./', ['tail', '-f', 'a.txt'], (line) => {
        this.buffer.insert_at_cursor(String(line) + '\n', -1);
    });
*/
}; 

//Run the application
let app = new App();
app.run(ARGV);