The problem I am getting is, when I enter the command,

su - root

at the beginning of my shell script file, it prompts the user to enter the password and then does NOT continue with the rest of the shell script. I then have to manually locate and run the shell script via terminal. I want the script to make sure that the user logs in as root and then continue with the rest of the shell script.

In other words, I want to run the script as any user but as soon as the script begins to execute, the user must change to root and then continue on with the rest of the script as root until it is done. Can this be done?

4 Answers 4


This is very easy to accomplish:

[ "$(whoami)" != "root" ] && exec sudo -- "$0" "$@"

When the current user isn't root, re-exec the script through sudo.

Note that I am using sudo here instead of su. This is because it allows you to preserve arguments. If you use su, your command would have to be su -c "$0 $@" which would mangle your arguments if they have spaces or special shell characters.

If your shell is bash, you can avoid the external call to whoami:

(( EUID != 0 )) && exec sudo -- "$0" "$@"
  • Sorry, I made an error in the explanation so it might have been misinterpreted. Here is a more clear explanation. Thanks for the help!
    – Redson
    May 29, 2014 at 17:28
  • @user68857 Your question was clear. This answer does exactly what you want.
    – phemmer
    May 29, 2014 at 17:30
  • i keep getting this error: sudo: must be setuid root
    – Redson
    May 29, 2014 at 17:32
  • i want to run the script as a regular user via terminal but the script should then switch the user to root until the end of the script
    – Redson
    May 29, 2014 at 17:37
  • @Nosscire if you're getting sudo: must be setuid root, then something happened to your sudo. To fix it: chmod u+s $(which sudo). And yes, I'm well aware of what you're trying to do, I do the same thing all the time in my scripts.
    – phemmer
    May 29, 2014 at 17:42

You can check the UID as well:

 if [ $(id -u) != 0 ]; then
     echo "You're not root"
     # elevate script privileges

You can call the script itself and check:

#! /bin/bash

if [ "root" != "$USER" ]; then
  su -c "$0" root

  • I think it will be more intuitive if the order swapped into [ "$USER" != "root" ]. Just another perspective I think.
    – Unknown123
    Jul 1, 2020 at 3:16

At the point where you want to login, simply add following command

sudo su

This is working perfectly with my code

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