Bash: Check if sudo

[ebbe]

This should be a easy question. I'm new to bash-scripting, but I want to play with it a bit.

I've made a script that can download a big file, and shutdown the computer afterwards, but to make it bulletproof, I want to check if the user wrote sudo in front of it, or else I cant shutdown the computer.

#!/bin/bash

if [[ $1 != "" ]]
then
        wget -c "$1";
        sudo shutdown -k 0;
else
        echo "Usage: sudo ./downloadAndShutdown <fileToDownload>";
fi

I already check to see if a file has been specified, but still I need to see if the script has the right privileges, and if not only print usage-message.

Ebbe

[visik7]

visi@lappy:~$ whoami 
visi
visi@lappy:~$ sudo whoami 
root

is enought ?

[ebbe]

visi@lappy:~$ whoami 
visi
visi@lappy:~$ sudo whoami 
root

It's perfect
Thanks.

[HackingYodel]

As a sidenote:

You could also use

if [ "$(id -u)" != "0" ]; then
	echo "Sorry, you are not root."
	exit 1
fi

With whoami being the same as id -un

if [ "$(whoami)" != "root" ]; then
	echo "Sorry, you are not root."
	exit 1
fi

Have fun scripting!

[Jessehk]

Even something like this:

ROOT_UID=0

if [ $UID != $ROOT_UID ]; then
    echo "You don't have sufficient privileges to run this script."
    exit 1
fi

[ebbe]

Thanks for the nice replies. I think I'm going for

if [ "$(whoami)" != "root" ]; then

It's easier to read.

And yes! My script works as expected

[hasimir44]

just wanted to say that this is a great idea..

[ebbe]

Just want to show you the final script. The only problem now, is that the file will have root as owner..
Maybe a chown should be thrown in there.

#!/bin/bash

whoami | grep "root" > /dev/null
if [ $? -eq 1 ] || [ "$1" = "" ]
then
	echo "Usage: sudo $0 <fileToDownload>";
	exit;
fi

wget -c "$1";
shutdown -P +3 "The shutdown can be stopped with: sudo shutdown -c";

[Mr. C.]

To use grep and produce no output, use the -q option:

$ grep -q root /etc/passwd
$ echo $?
0

No need to run whoami. You can just test the value of the environment variable UID:

$ sudo sh -c 'echo $UID'
0

Root UID is always 0. This makes your test:

if [ $UID -eq 0 ] ; then
  ...
fi

You can also use "id -u" to get the UID.



MrC