OS Address Book Exercise (With functions)

#Author - MR
#Date modified - 2/12/14

echo "Rosales,Clifford,123456,crosales@guidon.com" > addressbook
echo "Hizon,Joseph,654321,jhizon@batak.com" >> addressbook
echo "Raymundo,Miguel,789012,mraymundo@gmail.com" >>addressbook

until [ "$choice" == "4" ] #watch out for rookie mistakes
    do
        echo "======================"
        echo "What do you want to do?"
        echo "======================"
        echo "1. Add new record"
        echo "2. Display all records"
        echo "3. Search"
        echo "4. Exit"
        echo "======================"
        echo -n "Choice: "
        read choice
        echo

        # string -> "$x" == "y" --- int -> $x -eq y

        add_contact()
        {
            echo -n "Enter last name: "
            read last
            echo -n "Enter first name: "
            read first
            echo -n "Enter contact number: "
            read number
            echo -n "Enter email address: "
            read email
            echo "$last,$first,$number,$email" >> addressbook
            echo
            echo "~~~CONTACT SUCCESSFULLY ADDED~~~"
            echo
        }


        display_contacts()
        {
            cat addressbook | sed 's/,/ /g' | awk '{printf "%-15s%-15s%-15s%-15s\n",$1,$2,$3,$4}'
            echo
        }



        search()
        {
            echo -n "Entery query: "
            read query
            echo
            echo "SEARCH RESULTS:"
            echo
            cat addressbook | grep -i $query
            echo
        }


        invalid()
        {
            echo “INVALID CHOICE”
            echo
        }

        if [ $choice == "1" ]
        then
            add_contact
        elif [ $choice == "2" ]
        then
            display_contacts
        elif [ $choice == "3" ]
        then
            search
        elif [ $choice == "4" ]
        then
            echo "Auf wiedersehen"
            echo
        else
            invalid
        fi

    done