Exit status: http://tldp.org/LDP/abs/html/exit-status.html∞
0 is good and you can retrieve the last exit status using echo $?


#!/bin/sh
# this is a comment
echo "The number of arguments is $#"
echo "The arguments are $*"
echo "The first is $1"
echo "My process number is $$"
echo "Enter a number from the keyboard: "
read number
echo "The number you entered was $number"


Debug mode:
on: set -x
off: set +x