Detect remote or local connection from shell.

unreal128 · 07-28-2006, 10:10 PM

I have a script that runs on a network of systems. There is a feature in the script that allows users to connect to other systems. I want to disallow some features of the script if the user is already calling the script from a remote system (eg. calling script from telnet/ssh/konsole/xterm session.)

Is there a way to check from the shell to see if my session is remote or local? I used to use 'who am i' as a way to discover this but infortunately it doesn't work in X windows. I tried playing around with searching for the parent of $PPID (bash reserved variable) but this can get muddled since they can call any range of apps to connect remotely and I would have to exclusively search for them. I even tried calling up the terminal type attached to the shell via 'tty' but "pts/*" will show as my tty from a local X session or when connected remotely via telnet/ssh/konsole/xterm.

I basically want to...

Code:

 
if [ $detected_type_of_session -eq $true_condition ]; then
   runcodehere
else
   runcodethere
fi

Please help!

anomie · 07-28-2006, 10:33 PM

Would testing for a value in $DISPLAY be sufficient?

This assumes remote users aren't allowed to forward X displays over ssh. And it assumes local users are logging in to a X session.

Code:

if [[ -z "$DISPLAY" ]] ; then echo 'Aha! Remote user!' ; fi

Just one idea. Probably many ways to do it.

unreal128 · 07-29-2006, 12:13 PM

Good idea! I looked at the DISPLAY variable before but failed to realize values of display *:10 and up were remote. If I can't grab by 'who am i', I will defer to this variable. Thanks!