How do I determine if a shell script is running with root permissions?

Question

I've got a script I want to require be run with su privileges, but the interesting scripted command that will fail comes very late in the script, so I'd like a clean test up front to determine if the scrip will fail without SU capabilities.

What is a good way to do this for bash, sh, and/or csh?

Have you tried http://www.cyberciti.biz/tips/shell-root-user-check-script.html? — Nick ODell, Jun 15 '11 at 18:23
That looks pretty good. Why didn't you give this as an answer? :-) — F. Randall Farmer, Jun 15 '11 at 18:33
Possible duplicate of [How to check if running as root in a bash script](https://stackoverflow.com/questions/18215973/how-to-check-if-running-as-root-in-a-bash-script) — Nick ODell, Aug 05 '19 at 15:39

Nick ODell · Accepted Answer · 2019-10-21T06:20:07.623

16

bash/sh:

#!/usr/bin/env bash
# (Use #!/bin/sh for sh)
if [ `id -u` = 0 ] ; then
        echo "I AM ROOT, HEAR ME ROAR"
fi

csh:

#!/bin/csh
if ( `id -u` == "0" ) then
        echo "I AM ROOT, HEAR ME ROAR"
endif

edited Oct 21 '19 at 06:20

answered Jun 15 '11 at 18:36

Nick ODell

15,465
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32
66

3

This code will not work in a POSIX shell (`/bin/sh`). The `[[` command and `EUID` variable are specific to bash -- they're not defined in the POSIX specification. – Richard Hansen Jun 18 '11 at 07:55
2

Also #!/bin/bash is almost always wrong. If you must use bash (which is really not preferred) use /usr/bin/env bash – Good Person May 25 '13 at 15:31
2

It seems like bash **is** preferred by people who specifically mention bash in their questions. – jwg Mar 12 '14 at 16:11

score 12 · Answer 2 · answered Jun 15 '11 at 18:38

12

You might add something like that at the beginning of your script:

#!/bin/sh

ROOTUID="0"

if [ "$(id -u)" -ne "$ROOTUID" ] ; then
    echo "This script must be executed with root privileges."
    exit 1
fi

answered Jun 15 '11 at 18:38

mhoareau

631
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How do I determine if a shell script is running with root permissions?

2 Answers2