It is very easy to write additional commands for htsh. All commands are stored in directories inside the bin/ folder. For example, the following code is inside bin/cd/cd.php:

<?php
function htsh_cd($args) {
	if (isset($args['params'][0])) {
		if (is_dir($args['params'][0]) && @chdir($args['params'][0])) {
			$_SESSION['htsh']['cwd'] = getcwd(); //save cwd
			return array('result' => '');
		} else {
			return array('result' => "Error: I can't do that.");
		}
	} else {
		return array('result' => 'cd: usage: cd [dir]');
	}
}
?>

This is the function that handles the cd command. All functions should be named htsh_command where command is the name of the command. The function is passed an array based on the user's input. For example, if the user types cd a b -c -d e -f g h, htsh_cd will be passed the array:

Array(
  [options] => Array(
    [0] => c
    [1] => d
    [2] => f
  ),
  [params] => Array(
    [0] => a
    [1] => b
    [2] => e
    [3] => g
    [4] => h
  )
);

The function must return an array with the key 'result' containing the text that is to be outputted to the shell. If the key 'javascript' is specified, the value of 'result' will be evaluated by the client as javascript. See the edit and upload commands in the svn repository for two examples of returning javascript.