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Crontab entry to shutdown if no users

Hello,

I have an Ubuntu 8.04 server that supplies gnump3d tunes, some http and serves as a test bed into my somewhat recent fascination with Linux. I love the flexibility of the platform and really enjoy rocking the CLI.

My question is: How can I write a script that will check to see if I am logged in and if it returns negative, shutdown the server.

I have tried (and forgive my ignorance, please. I have witnessed the awesome power of people helping with Linux and I must say it is amazing):

Code:

#!/bin/bash



if [ users=drew ]

  then 

      echo You are logged in

  else

      shutdown -P now

fi

Now, as I understand, when I add this to /etc/crontab, It needs to be run by a user so I tried:

Code:

30 23 * * * * root NightKill

Whereas 'NightKill' is the script name.

If I have an extra *, disregard it. I wasn't copying from my actual crontab. How does one get this to work? I have googled, I have searched, I am new. Any help is appreciated.

/drew

I don't really understand what the problem is. The syntax of your script is clearly wrong because it lacks the "command substitution". Anyway, you can test if a particular user is logged in, by means of the w command, e.g.

Code:

#!/bin/bash

user=drew

if [ -z "$(w -h $user)" ]

then

  echo user $user is not logged in

else

  echo user $user is logged in

fi

Then just add your script to the root's crontab. Note that you have to use the full path of the /sbin/shutdown command, because of the limited environment of cron (the PATH is limited to /bin:/usr/bin).

Thank you colucix and JZL240I-U.

I guess I was trying to use the output from the users command to test if I was logged in. I should have been more clear. JZL240I-U I have made it about half way through the first two sites you mentioned, I must just need to pay more attention.

Thanks again

/drew