Bash Script to install PostgreSQL - Failing

I built this deployment script which runs when my debian 6.0 server is deployed. I have shown it here before (this is a linode stackscript incase anyone else is wondering):

#!/bin/bash
#
# Install PostgreSQL
#
# Copyright (c) 2010 Filip Wasilewski <[email protected]>.
#
# My ref: http://www.linode.com/?r=aadfce9845055011e00f0c6c9a5c01158c452deb

function postgresql_install {
    aptitude -y install postgresql postgresql-contrib postgresql-dev libpq-dev
}

function postgresql_create_user {
    # postgresql_create_user(username, password)
    if [ -z "$1" ]; then
        echo "postgresql_create_user() requires username as the first argument"
        return 1;
    fi
    if [ -z "$2" ]; then
        echo "postgresql_create_user() requires a password as the second argument"
        return 1;
    fi

    echo "CREATE ROLE $1 WITH LOGIN ENCRYPTED PASSWORD '$2';" | sudo -i -u postgres psql
}

function postgresql_create_database {
    # postgresql_create_database(dbname, owner)
    if [ -z "$1" ]; then
        echo "postgresql_create_database() requires database name as the first argument"
        return 1;
    fi
    if [ -z "$2" ]; then
        echo "postgresql_create_database() requires an owner username as the second argument"
        return 1;
    fi

    sudo -i -u postgres createdb --owner=$2 $1
}

postgresql_install
postgresql_create_user(username, password)
postgresql_create_database(dbname, username)

I deployed my server with this script, which was built on top of Filip's version, but then when I try to see if postgresql is running by typing pg_ctl it says command not found.

Where I have I gone wrong on this? Since it deploys when the server runs I am not able to see where it is going wrong.