bash code snippets

This is going to be a collection of bash code snippets:

1. Check if the user running the script is root:
   
   # make sure we're running as root
if [ `id -u` != 0 ]; then { echo "Sorry, must be root.  Exiting..."; exit; } fi
2. Check the successful execution of previous command:
   
   if (( $? )); then
        {
                echo "could not executed successfully";
                exit;
        }
fi;
3. Check number of arguments:
   
   # Check for proper number of command line args.

EXPECTED_ARGS=1
E_BADARGS=65

if [ $# -ne $EXPECTED_ARGS ]
then
  echo "Usage: `basename $0` {arg}"
  exit $E_BADARGS
fi
4. Array loops:
   
   VALUES=("value1" "value2" "value3" "..." "valueN")

for ((i=0; i<${#VALUES[@]}; i++))
do
  echo ${VALUES[$i]}
done