shell - How to check if running as root in a bash script

Question

I'm writing a script that requires root level permissions, and I want to make it so that if the script is not run as root, it simply echoes "Please run as root." and exits.

Here's some pseudocode for what I'm looking for:

if (whoami != root)
  then echo "Please run as root"

  else (do stuff)
fi

exit

How could I best (cleanly and securely) accomplish this? Thanks!

Ah, just to clarify: the (do stuff) part would involve running commands that in-and-of themselves require root. So running it as a normal user would just come up with an error. This is just meant to cleanly run a script that requires root commands, without using sudo inside the script, I'm just looking for some syntactic sugar.

Answer 1

The $EUID environment variable holds the current user's UID. Root's UID is 0. Use something like this in your script:

if [ "$EUID" -ne 0 ]
  then echo "Please run as root"
  exit
fi

Note: If you get 2: [: Illegal number: check if you have #!/bin/sh at the top and change it to #!/bin/bash.