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 exit

Answer 1

A few answers have been given, but it appears that the best method is to use is:

• id -u
• If run as root, will return an id of 0.

This appears to be more reliable than the other methods, and it seems that it return an id of 0 even if the script is run through sudo.

Answer 2

There is a simple check for a user being root.

The [[ stuff ]] syntax is the standard way of running a check in bash.

error() {
  printf '\E[31m'; echo "$@"; printf '\E[0m'
}

if [[ $EUID -eq 0 ]]; then
    error "Do not run this as the root user"
    exit 1
fi

This also assumes that you want to exit with a 1 if you fail. The error function is some flair that sets output text to red (not needed, but pretty classy if you ask me).

Answer 3

If the script really requires root access then its file permissions should reflect that. Having a root script executable by non-root users would be a red flag. I encourage you not to control access with an if check.

chown root:root script.sh
chmod u=rwx,go=r script.sh

Answer 4

id -u is much better than whoami, since some systems like android may not provide the word root.

Example:

# whoami
whoami
whoami: unknown uid 0

Answer 5

#!/bin/bash

# GNU bash, version 4.3.46
# Determine if the user executing this script is the root user or not

# Display the UID
echo "Your UID is ${UID}"

if [ "${UID}" -eq 0 ]
then
    echo "You are root"
else
    echo "You are not root user"
fi

Editor's note: If you don't need double brackets, use single ones for code portability.