Apply gitignore to existing Git repository

Problem

We have existing git repository which contains e.g. .net projects written in C# and we want to apply gitignore rules.

Solution
At the beginning we need to crate our own ignore rules or download predefined from https://github.com/github/gitignore.
In this case I prefer download predefined file: VisualStudio.gitignore and put in my existing git repository.

Don't forget commit all pending changes. After that run below commands

git rm -r --cached .

Below command removes everything from the index

git add .
git commit -m ".gitignore is now working"

How to extend VirtualBox partition - Windows XP example

The Problem

Due to insufficient free space in my one of my Virtual Machines running under Windows XP I would like to extend existing disk image.
I originally created a 10GB virtual disk image, but soon realized that it isn't enough space.

The solution

1. Extend disk image using VBoxManage

Open command line (under windows 8 without Administrator privileges) and run command:

VBoxManage modifyhd Windows XP.vdi --resize 20480

where:

• Windows XP.vdi is the name of disk image file
• 20480 new size in MB (in this case 20 GB)

2. Extend the NTFS partition

Although we extended the physical disk image, Windows XP still shows it's partition as 10GB.
We need to extend the NTFS partition into the new size.
To achieve that I downloaded the free GParted Live CD ISO image and attached it to my virtual machine.
Restart VM and set up new size.

2. Reboot Windows

Close VM and remove the ISO image from the Storage menu.
Start VM again and now Windows XP is starting up with check disk.
I got no errors message and Windows correctly recognizes new bigger partition.

Generic Int to Enum Converter - WPF example

I'm proud to present how to convert integer value to any enum you ever would like to :-)
Below example ilustrates use it e.g in WPF application.
We need to create Converter class as showed below. And of course create some enums

    public class GenericIntToEnumConverter : IValueConverter
    {
        public object Convert(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            if (((Type)parameter).IsEnum && value is int)
            {
                return Enum.GetName((Type)parameter, value);
            }
            return null;
        }



        public object ConvertBack(object value, Type targetType, object parameter, System.Globalization.CultureInfo culture)
        {
            return (int)value;
        }
    }



    public enum ExampleEnum
    {
        First = 1,
        Second =2,
        Third =3
    }

Usage is very easy we just pass as the parametr the destination enum:

Deploy SQLite .net application

Below I describe how to configure C# .net application to work with SQLite database client.
First download and install sqlite ado.net provider. Then include to your project configuration below settings:

Add to project references files:

• SQLite.Designer
• System.Data.SQLite
• System.Data.SQLite.Linq

and set property 'Copy Local' value equal true for each of them.
Enjoy.

C# Command Line Arguments Parser

There is probably several good ways to parse command line arguments in C# console application. But when I encountered such problem in my work first what I thought was to stop inventing wheel once again :-)
After short research I realized that in most cases I need lightweight reusable code which I can easily adapt for current requirements. At first I found ConsoleFx library. After short code analysis I was sure that it looks really good for me but... In my opinion it's heavy: a lot of classes with really reach functionality. So that wasn't exactly what I need because I also required lightweight solution. And then I found sample of small handler which is great and you will find it below.

So how is the magic happens?

 args.Process(
                () => Console.WriteLine("Usage is switch1=value1,value2 switch2=value3"),
                new CommandLine.Switch("switch1",
                    val => Console.WriteLine("switch 1 with value {0}",
                        string.Join(" ", val))),
                new CommandLine.Switch("switch2",
                    val => Console.WriteLine("switch 2 with value {0}",
                        string.Join(" ", val)), "s1"));
        }

All of the magic happens inside the Process method, where the query tries to match the arguments against the ones we want to check for. The .Sum() aggregate method does two things. It enumerates the elements of the IQueryable, actually calling the handlers in the process. Nothing happens till then! Each of the InvokeHandler calls returns 1, so the result of the .Sum() is 0 if there were no matches (which is when we call the supplied printUsage handler).

using System;
using System.Collections.Generic;
using System.Linq;
using System.Text;
using System.Text.RegularExpressions;
using System.Threading.Tasks;

namespace SampleConsoleApplication
{
    /* Simple commandline argument parser written by Ananth B.
    http://www.ananthonline.net */
    static class CommandLine
    {
        public class Switch // Class that encapsulates switch data.
        {
            public Switch(string name, Action<IEnumerable<string>> handler, string shortForm)
            {
                Name = name;
                Handler = handler;
                ShortForm = shortForm;
            }

            public Switch(string name, Action<IEnumerable<string>> handler)
            {
                Name = name;
                Handler = handler;
                ShortForm = null;
            }

            public string Name
            {
                get;
                private set;
            }
            public string ShortForm
            {
                get;
                private set;
            }
            public Action<IEnumerable<string>> Handler
            {
                get;
                private set;
            }

            public int InvokeHandler(string[] values)
            {
                Handler(values);
                return 1;
            }
        }

        /* The regex that extracts names and comma-separated values for switches 
        in the form (<switch>[="value 1",value2,...])+ */
        private static readonly Regex ArgRegex =
            new Regex(@"(?<name>[^=]+)=?((?<quoted>\""?)(?<value>(?(quoted)[^\""]+|[^,]+))\""?,?)*",
                RegexOptions.Compiled | RegexOptions.CultureInvariant |
                RegexOptions.ExplicitCapture | RegexOptions.IgnoreCase);

        private const string NameGroup = "name"; // Names of capture groups
        private const string ValueGroup = "value";

        public static void Process(this string[] args, Action printUsage, params Switch[] switches)
        {
            /* Run through all matches in the argument list and if any of the switches 
            match, get the values and invoke the handler we were given. We do a Sum() 
            here for 2 reasons; a) To actually run the handlers
            and b) see if any were invoked at all (each returns 1 if invoked).
            If none were invoked, we simply invoke the printUsage handler. */
            if ((from arg in args
                 from Match match in ArgRegex.Matches(arg)
                 from s in switches
                 where match.Success &&
                     ((string.Compare(match.Groups[NameGroup].Value, s.Name, true) == 0) ||
                     (string.Compare(match.Groups[NameGroup].Value, s.ShortForm, true) == 0))
                 select s.InvokeHandler(match.Groups[ValueGroup].Value.Split(','))).Sum() == 0)
                printUsage(); // We didn't find any switches
        }
    }
}

Author Licence

The code above is for you to do whatever you want to. Even if it blows you up (like Dr. Manhattan blows Rorschach up), don’t come back from the dead to haunt me. I would, however appreciate it if you kept the comment attributing that code to me.

My comments So far I haven't found any bugs in such code. Click here to go to my repository with appropriate unit tests

How set up WOL (Wake On Lan) on Thin Client with ubuntu

I set up small home server using HP TERMINAL HP T5000 (Thin Client). I installed Ubuntu server on it. It works great - but recently I realized that I need to have this server up only for very limited number of scenarios i.e. when I'm working on one of my PCs (so I want to have access to server resources e.g. samba, cups, DNS server etc) or I'm downloading something from the internet using transmission-daemon. To optimize my server power consumption I decided to set up Wake On Lan on my ubuntu and wrote 2 simple scripts in ruby.

How to set up WOL on ubuntu?
Log in as administrator.
Install ethtool:

sudo apt-get install ethtool

Change to the startup script directory and start editing a new file:

cd /etc/init.d/
nano wakeonlanconfig

Paste, or type this into the file, replacing eth0 with your network device, repeat the ethtool line as many times for your devices before the exit line:

#!/bin/bash
ethtool -s eth0 wol g
exit

Set the permissions of the file:

chmod a+x wakeonlanconfig

Make the script run on startup:

update-rc.d -f wakeonlanconfig defaults

You should see something like:

 Adding system startup for /etc/init.d/wakeonlanconfig ...
   /etc/rc0.d/K20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc1.d/K20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc6.d/K20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc2.d/S20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc3.d/S20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc4.d/S20wakeonlanconfig -> ../init.d/wakeonlanconfig
   /etc/rc5.d/S20wakeonlanconfig -> ../init.d/wakeonlanconfig

Now finish by running it, and making sure there are no errors.

/etc/init.d/wakeonlanconfig

Now when the server can be started remotely I want to present you 2 scrips which I wrote in ruby to make my life easier.

First for client machines.
All I need to do in this script is checking state of my server and if it is down send magic packet to power it on.

begin
  require 'Win32/Console/ANSI'
rescue LoadError
  raise 'You must gem install win32console to use color on Windows'
end

require 'logger'
require 'net/ping'
require File.dirname(__FILE__) + "/wakeonlan.rb"

class String
    def red; colorize(self, "\e[1m\e[31m"); end
    def green; colorize(self, "\e[1m\e[32m"); end
    def dark_green; colorize(self, "\e[32m"); end
    def yellow; colorize(self, "\e[1m\e[33m"); end
    def blue; colorize(self, "\e[1m\e[34m"); end
    def dark_blue; colorize(self, "\e[34m"); end
    def pur; colorize(self, "\e[1m\e[35m"); end
    def colorize(text, color_code)  "#{color_code}#{text}\e[0m" end
end

log = Logger.new(File.dirname(__FILE__) + '/logs/log.txt', 'monthly')
log.debug "Script has been started"

puts "Ping ubuntu server"
log.debug "Ping ubuntu server"
p = Net::Ping::TCP.new('my_server_IP', 'http').ping?

if !p
 puts "Getting server up"
 log.debug "Getting server up"
 puts "Sending magic packet to ubuntu server"
 wol=WakeOnLan.new
 wol.wake("my_server_mac_address", "broadcast", "my_server_IP")
 # args: MAC_address Broadcast IP_address
 wol.close
else
 puts "Server is running".dark_green
 log.debug "Server is running"
end

Below I present code for WakeOnLan class which I used in above code:

# K.Kodama 2003-04-20 revised/bug fix
# K.Kodama 2000-05-10
# This program is distributed freely 
# in the sense of GNU General Public License or ruby's.

require "socket"

class WakeOnLan
 attr :socket
 def initialize
  @socket=UDPSocket.open()
  @socket.setsockopt(Socket::SOL_SOCKET,Socket::SO_BROADCAST,1)
 end;
 def close; @socket.close; @socket=""; end
 def wake(mac_addr, broadcast="", ip_addr="")
  wol_magic=(0xff.chr)*6+(mac_addr.split(/:/).pack("H*H*H*H*H*H*"))*16
  if broadcast==""; # Set broadcast. Assume that standard IP-class.
   ips=ip_addr.split(/\./);c=ips[0].to_i
   if c<=127; ips[1]="255";end # class A:1--127
   if c<=191; ips[2]="255";end # class B:128--191
   if c<=223; ips[3]="255";end # class C:192--223
   # class D:224--239 multicast
   broadcast=ips.join(".")
  end
  3.times{ @socket.send(wol_magic,0,broadcast,"discard") }
 end
end

if $0 == __FILE__
=begin
Sample for WakeOnLan class.
Use as: ruby wakeonlan.rb [broadcast_address] < data_text
line format of data_text: ip-address  hostname  MAC-address
Data sample: 10.20.30.40  wake-pc  100:110:120:130:140:150
Note.  To check WOL packet, use tcpdump -x.
=end

 if ARGV.size>=1; broadcast=ARGV[0]; ARGV.clear; else broadcast=""; end
 wol=WakeOnLan.new
 while gets
  ip,name,hw=$_.sub(/^\s+/,"").split(/\s+/)
  wol.wake(hw, broadcast, ip)
 end
 wol.close
end

Second for server.
I'm checking here state of network i.e. if any of my PCs is working. In case when all my PCs are offline server could be turn off but before I'll send halt command I have to check status of transmission-daemon - check if there are any elements being downloaded at the moment. If all conditions passed server is going to be shut down.

require 'net/ping'
require 'logger'
require 'transmission_api'

class TorrentStatus
 attr_accessor :all_torrents_finished
 
 def initialize()
  @transmission_api = TransmissionApi.new(
   :username => "my_user",
   :password => "password",
   :url      => "http://myserver:9091/transmission/rpc"
  )
  
  torrents = @transmission_api.all

  @all_torrents_finished = true
  torrents.each{|t|
   #puts "#{t["name"]} - [#{t["percentDone"]}]"
   @all_torrents_finished &= (t["percentDone"] == 1)
  }
  end
end

class LanStatus
 
 def initialize()
  @interfaces = ["192.168.zzz.xxx","192.168.zzz.yyy"]
 end
 
 def active_computers_in_network?
  active = false
  @interfaces.each{|ip|
   active |= Net::Ping::External.new(ip).ping?
  }
  active
 end
 
end

log = Logger.new(File.dirname(__FILE__) + '/logs/shutdown_log.txt')
log.debug "Script has been started"

puts "Checking system state"
log.debug "Checking system state"
print " * Torrent status "
torrent_status = TorrentStatus.new
all_torrents_finished = torrent_status.all_torrents_finished
puts "- [#{all_torrents_finished ? "idle" : "active"}]"

log.debug " * Torrent status - [#{all_torrents_finished ? "idle" : "active"}]"

print " * Lan status"
lan_status = LanStatus.new
active_computers_in_network = lan_status.active_computers_in_network?
puts "- [#{active_computers_in_network ? "active" : "inactive"}]"

log.debug " * Lan status - [#{active_computers_in_network ? "active" : "inactive"}]"

if (all_torrents_finished && !active_computers_in_network)
 puts "Sending HALT command to system"
 log.debug "Sending HALT command to system"
 system "sudo shutdown -h now"
end

There was still problem how to make it automated process. From the server side i use cron to schedule job which will execute in every 5 minutes and run ruby script. To read more about setting cron please read this post.
I added to crontab below entry:

0/5 * * * * ruby /home/luke/scripts/shut_down.rb

All my clients work under windows system and they are not attached to domain. So i just added ruby script to logon scripts. To add logon script for Windows 7 Home Premium: I've created a script at C:\Windows\System32\repl\import\scripts\start.bat Which executes command:

ruby /path_to_my_script/login.rb

Then I invoked from command line

net user USERNAME /scriptpath:start.bat

How to schedule Cron to run jobs every 5 Minutes, 12 hours, etc.

Linux Crontab Format

MIN HOUR DOM MON DOW CMD

Schedule a job for more than one instance (e.g. twice a day)

Below example executes the specified script (send_reports.rb) at 10:00 and 16:00 on every day. The comma separated value in a field specifies that the command needs to be executed in all the mentioned time.

00 10,16 * * * ruby /home/luke/scripts/send_reports.rb

00 – 0th Minute (Top of the hour)
10,16 – 10 AM and 4 PM
* – Every day
* – Every month
* – Every day of the week

Schedule a job for specific range of time (e.g. only on weekdays)

To schedule a job to be ran for every hour with in a specific range of time then use the following. This example checks the status of the server everyday (including weekends) during the working hours 10 a.m – 3 p.m

00 10-15 * * * ruby /home/luke/scripts/check-server-status.rb

00 – 0th Minute (Top of the hour)
10-15 – 10 am,11 am, 12 am, 1 pm, 2 pm, 3 pm
* – Every day
* – Every month
* – Every day of the week

Execute a job every 5 minutes

*/5 * * * * /home/luke/scripts/do_work.sh

In the same way, use */10 for every 10 minutes, */15 for every 15 minutes, */30 for every 30 minutes, etc.

Execute a job every 5 hours

0 */5 * * * /home/luke/scripts/backup.sh

In the same way, use */2 for every 2 hours, */3 for every 3 hours, */4 for every 4 hours, etc. Table: Cron special keywords and its meaning
Keyword Equivalent
@yearly 0 0 1 1 *
@daily 0 0 * * *
@hourly 0 * * * *
@reboot Run at startup.

Schedule a job for first minute of every year using @yearly

When you want a job to be executed on the first minute of every year, then you can use the @yearly cron keyword in way shown below.

@yearly /home/luke/scripts/sell-db-annual-maintenance

This configuration execute the financial database annual maintenance using sell-db-annual-maintenance shell script at 00:00 on Jan 1st for every year.

Schedule a background job every day using @daily

Use the @daily cron keyword to do a daily backup file using backup-invoices shell script at 00:00 on every day.

@daily /home/luke/scripts/backup-invoices "day started"