Question

My shell script is as shown below:

#!/bin/bash

# Make sure only root can run our script
[ $EUID -ne 0 ] && (echo "This script must be run as root" 1>&2) || (exit 1)

# other script continues here...

When I run above script with non-root user, it prints message “This script…” but it doe not exit there, it continues with the remaining script. What am I doing wrong?

Note: I don’t want to use if condition.

Answer 1

You’re running echo and exit in subshells. The exit call will only leave that subshell, which is a bit pointless.

Try with:

#! /bin/sh
if [ $EUID -ne 0 ] ; then
    echo "This script must be run as root" 1>&2
    exit 1
fi
echo hello

If for some reason you don’t want an if condition, just use:

#! /bin/sh
[ $EUID -ne 0 ] && echo "This script must be run as root" 1>&2 && exit 1
echo hello

Note: no () and fixed boolean condition. Warning: if echo fails, that test will also fail to exit. The if version is safer (and more readable, easier to maintain IMO).