LDP/LDP/guide/docbook/abs-guide/am-i-root.sh

#!/bin/bash
# am-i-root.sh:   Am I root or not?

ROOT_UID=0   # Root has $UID 0.

if [ "$UID" -eq "$ROOT_UID" ]  # Will the real "root" please stand up?
then
  echo "You are root."
else
  echo "You are just an ordinary user (but mom loves you just the same)."
fi

exit 0


# ============================================================= #
# Code below will not execute, because the script already exited.

# An alternate method of getting to the root of matters:

ROOTUSER_NAME=root

username=`id -nu`              # Or...   username=`whoami`
if [ "$username" = "$ROOTUSER_NAME" ]
then
  echo "Rooty, toot, toot. You are root."
else
  echo "You are just a regular fella."
fi