Notes

Automatic login with SSH private key in PuTTY

These steps will enable you to automatically login to a remote computer through SSH protocol with PuTTY.

• Run PuTTYgen and generate a new SSH-2 RSA key.
• Enter some comment and a passphrase.
• Save the private key to your.ppk file.
• Copy the public key from the text field which looks like ssh-rsa AAA… to the clipboard. Save it to your remote computer at $HOME/.ssh/authorized_keys file. Make sure the key can be read/written by your user: chmod -R 600 .ssh.
• Run Pageant, click Add key, select your.ppk file and enter the passphrase. Don’t forget it. You’ll have to reenter the passphrase every time you run Pageant.
• Time to open up PuTTY. Under Connection / SSH / Auth category select your.ppk in the field Private key for your authentication. You may also want PuTTY to choose the username for you. It can be set under Connection / Data category.
• Connect!

This trick might not work if your user’s home directory is shared with another user from the same group but unfortunately .ssh and authorized_keys are owned by him. Those need group read and write (660) permissions. However, sshd needs requires 600 permissions. This can be bypassed by setting StrictModes to no at /etc/ssh/sshd_config. Security may suffer, but hey - you have to do what you have to do, right?

Setup Subversion on CentOS and connect through svn+ssh in Eclipse

These steps describe how to establish SVN collaboration environment on Linux CentOS server and Eclipse IDE.

Server configuration

• Create a shared directory dedicated to SVN users: http://www.cyberciti.biz/faq/linux-setup-shared-directory/.
• Install Subversion on your server: yum install subversion (don’t forget do sudo if not logged in as root).
• Create a repo directory: mkdir $HOME/some-repo ($HOME stands for /home/some-user).
• Establish a repository: svnadmin create $HOME/some-repo

Eclipse configuration

• Download Eclipse Subversive from http://download.eclipse.org/releases/indigo.
• Right-click on your project in the Package Explorer and choose menu item Team / Share project.
• In the wizard, select SVN. Install SVN connectors if needed.
• Provide the following data:
  • URL: svn+ssh://some-user@example.com/home/some-user/some-repo
  • Username: some-user
  • And user’s password.
• Do the initial commit or checkout depending on where the existing code is located.

Single (monolithic) controllers in OOP

Sometimes I need to do some fancy coding in PHP but do not want to overcomplicate my projects with all those trending tools and frameworks. I simply scrape a single class which provides project’s functionality within its scope.

Now I know it’s not the best practice to write monolithic controllers, but seriously, I’m not doing anything nasty either. A lot of `monolithic` things are awesome, e.g. this “Nokia 3310” phone; it’s handy and durable.

This is a perfectly valid PHP script:

<?php

global $data;

function get_some() {
	global $data;
	$data = 'A well known fact';
}

function get_all() {
	global $data;
	$data .= ' and a secret';
}

function login() {
	// Check login...
	return TRUE;
}

get_some();

if(login()) {
	get_all();
}

echo $data;

There’s nothing wrong with this CodeIgniter MVC controller either:

<?php

class Home extends CI_Controller {

	public function __construct()
	{
		parent::__construct();

		$this->load->model('User_model');
		$this->load->model('Data_model');
		// Model implementation is arbitrary...
	}

	public function index()
	{
		$this->Data_model->get_some();

		if($this->User_model->login())
		{
			$this->Data_model->get_all();
		}

		$this->Data_model->print_data();
	}

}

Instead of going dirty with procedural PHP or overcomplicating it with a MVC framework, you may consider writing your app as a class (and instantiate it afterwards). As in (almost) every MVC controller, the point is to have all available resources at your disposal within a single class avoiding the use of global $variables. No separate files for a small project is also a plus.

Here we go:

<?php

class App {

	private $data;

	public function __construct() {
		$this->get_some();

		if($this->login()) {
			$this->get_all();
		}

		echo $this->data;
	}

	public function get_some() {
		$this->data = 'A well known fact';
	}

	public function get_all() {
		$this->data .= ' and a secret';
	}

	public function login() {
		// Check login...
		return TRUE;
	}

}

$app = new App();

Quite neat, isn’t it?

Maintaining JavaScript float precision

Sometimes in JavaScript (and other languages) float numbers lose precision, e.g. 1.991 * 100 would be 199.10000000000002. That happens due to CPU limitations. Quite brutal but effective solutions exists.

function maintainFloatPrecision(number) {
	if(number%1 == 0) { // Check if number has a remainder.
		return number;
	} else {
		var str = "" + number;
		if(str.match(/\d+\.\d*0{6,}\d/)) {
			pos = str.search(/0{6,}\d/g);
			return number.toFixed(pos - 2);
		} else if(str.match(/\d+\.\d*9{6,}\d/)) {
			pos = str.search(/9{6,}\d/g);
			return parseFloat(number.toFixed(pos - 1));
		} else {
			return number;
		}
	}
}

Note: This function proves that 100 ÷ 3 × 3 = 100. :)

yum tips

• Configuration is usually located at /etc/yum.conf or /etc/yum.repos.d
• Config parameter exclude filters out packages according to a wildcard, e.g. exclude=*.i386 *.i586 *.i686 excludes packages of 32 bit architectures.
• If you change config parameter keepcache from 0 to 1, all downloaded RPMs will be cached at /var/cache/yum.

Using Bitbucket with Eclipse and msysgit

1. Register at Bitbucket (https://bitbucket.org/).
2. Install msysgit (http://code.google.com/p/msysgit/).
3. Get a SSH key (in Git Gui tool click menu Help / Show SSH Key) and add it to your Bitbucket account (https://bitbucket.org/account/).
4. Create/clone your repo as shown in Doug’s videos: 1st video, 2nd video.