Am I root?

Root privileges is important when doing system wide installation and configuration. How do we determine the script is being run by a root or normal user?

# Check that we are run as root.
# Return 0 if yes, or 1 if not or undeterminable.
function is_root() {
  uid=$(id -u 2> /dev/null)

  if [ -n "$uid" ]; then
    if [ "$uid" != "0" ]; then
      echo "FAILED: You need root privileges to run this script.";
      echo
      return 1
    fi
  else
    echo "Could not detect UID";
    return 1
  fi
}