Shell Programming and Scripting

I have 2 separate Bourne shell scripts with 2 questions in Sun O/S & UNIX environment.

Question 1: One of the scripts is supposed to be executed by "root" user only but cannot be executed after user executes "su - oracle". How can I check in the script whether the current user is "root" user? "who am i" does not prevent the user from executing this script after executing "su - oracle".

Question 2: This is opposite of question 1. The other script should be executable only if the "root" user executes "su - oracle". How can I prevent the script from continue execution if the user does not execute "su - oracle"?

Install your scripts in a non-NFS-mounted directory. Set ownership (chown) both scripts to root. Allow only root to execute the first script (chmod og-x). Allow anyone to run the second script (chmod og+rx). Now, in the SECOND script, you can check to see if it's root running, and exit if so:

Code:

test `id -u` = 0 && exit 2;

(Using this code only works to prove that you are NOT root. Proving that you are root is better left to the Operating System.) Feel free to engineer your own error message.

Thanks a lot. I think "id -u" works perfectly for me to use in both cases.

Just found out "id -u" does not work in some of the machines. Not really sure why. Could be due to individual machine's configuration issue. Not very safe for me to use.

Found the following command from a colleague with some modification by myself. It seems more reliable for me:

env | grep 'USER='| sed 's/USER=//'

This one can check for both "oracle", "root" or whatever user you want to check.

Thanks to otheus anyway as I have learnt something new.

In that case, hardcode the path:

/usr/bin/id -u

Or always use the GNU version:

/usr/local/bin/id -u # if id is the GNU version installed in /usr/local/bin.

You can get it from coreutils.

Alternatively, you can get it from ps:

Code:

$ ps u $$ |awk 'NR == 2 { print $1 }'
10362

It could be you get a name, in which case you then get it from getent:

Code:

getent `ps u $$ |awk 'NR == 2 { print $1 }'` passwd

Thanks, otheus.

I tried the following commands and the results are as follows. It's not really the command "id" cannot be found but it's the "-u" option giving problem (except when I used /usr/local/bin/). It's no longer a problem for me in the script using the method I mentioned in the previous post but I am just curious about "id -u" - my colleague also complains about facing similar problem with "id" command...so he avoids using it in our machines.

Command: id -u
Result:
id: illegal option -- u
Usage: id [-ap] [user]

Command: /usr/bin/id -u
Result:
/usr/bin/id: illegal option -- u
Usage: id [-ap] [user]

Command: /usr/local/bin/id -u
Result:
/usr/local/bin/id: Command not found.


Any idea what could have caused "-u" option not being recognised?

Right, so download and install GNU coreutils. This might mean getting other GNU utils as well, such as make.