Linux Shell Script Example

#!/bin/bash
#For beginners who want a better understanding of shell scripting on Linux systems
#Coded on Ubuntu 16.04+
#Execute script in terminal: bash /path/to/script.sh or ./path/to/script.sh
clear

# INITIALIZATION
echo -e '\033]2;Terminal\007'

KEY=$RANDOM

until [[ $sac == $KEY ]] ; do
clear
read -p "Session Access Key: " sac
if [[ $sac == "/grant" ]] ; then
    echo
    echo $KEY
    sleep 2
elif [[ $sac == $KEY ]] ; then
    echo
    echo Access granted!
    sleep 1
else
    echo
    echo Access Denied!
    exit 0
fi
done

# FUNCTIONS
doFunc1() {
    echo "This is the first function."
    sleep 1
}

doFunc2() {
    echo "This is the second function."
    sleep 1
}

doFunc3() {
    echo "This is the third function."
    sleep 1
}

# MAIN LOOP
while true ; do
clear
echo "1) doFunc1"
echo "2) doFunc2"
echo "3) doFunc3"
echo
read -p '$ ' opt
case "$opt" in
    "1")
        doFunc1 ;;
    "2")
        doFunc2 ;;
    "3")
        doFunc3 ;;
    *)
        echo "This is not a function."
        sleep 1 ;;
esac
done