bash: fail if script is not being run by root

Question

I have a bash script that installs some software. I want to fail as soon as possible if it is not being run by root. How can I do that?

Although I would generally consider this silly behavior: Let it run until permissions fail; the system may be setup such that the operation can be performed successfully as the current user and by forcing root this option is taken away [I've had to fix scripts that have made similar assumptions before]. On the other hand, I such much more of a case to prevent access or display a big fat warning if run as root. — user166390
– user166390, Commented Oct 29, 2009 at 6:55
You should try using sudo. Under linux, when you install anything you need to be root to prevent normal users installing anything that may damage the system — Eligio Becerra
– Eligio Becerra, Commented Oct 29, 2009 at 7:01
He wants his script to take into account that some people may forget, or be unaware of sudo (or other means of privilege escalation). Its good practice to check for run time sanity before attempting to do anything else. — user50049
– user50049, Commented Oct 29, 2009 at 7:04

David Brown · Accepted Answer · 2009-10-29 06:44:13Z

29

#!/bin/bash
if [ "$(id -u)" != "0" ]; then
   echo "This script must be run as root" 1>&2
   exit 1
fi

Source: http://www.cyberciti.biz/tips/shell-root-user-check-script.html

answered Oct 29, 2009 at 6:44

David Brown

36.4k12 gold badges91 silver badges139 bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

zlack Over a year ago

or, to keep it shorter check the UID env: if [[ $UID -ne 0 ]]; then

pr1001 Over a year ago

@zlack $UID will give the original user's UID if the script is run via sudo while David's will consider the script as being run as root. Depending on what you're doing, David's is probably better.

Tom Over a year ago

As pr1001 says, UID will not work if the user is running the script using sudo, but EUID will work just fine.

Community · Accepted Answer · 2017-04-13 12:22:38Z

10

After digging around on this, the consensus seems to be that there is no need to use id -u in bash, as the EUID (effective user id) variable will be set. As opposed to UID, the EUID will be 0 when the user is root or using sudo. Apparently, this is around 100 times faster than running id -u:

#!/bin/bash
if (( EUID != 0 )); then
    echo "You must be root to do this." 1>&2
    exit 1
fi

Source: https://askubuntu.com/questions/30148/how-can-i-determine-whether-a-shellscript-runs-as-root-or-not

edited Apr 13, 2017 at 12:22

CommunityBot

11 silver badge

answered Jun 24, 2012 at 10:27

Tom

4,79028 silver badges33 bronze badges

1 Comment

Janus Troelsen Over a year ago

this doesn't work in the Bourne shell though. do you have any strictly POSIX compliant solutions?

Collectives™ on Stack Overflow

bash: fail if script is not being run by root

2 Answers 2

3 Comments

1 Comment

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

2 Answers 2

3 Comments

1 Comment

Your Answer

Sign up or log in

Post as a guest

Related