shell quesition: How can I tell whether script is running in background?

[Jack C. Mahaffey]

I want to put a short script together that can be executed to determine if the calling script is currently running in background rather than interactive.

I've got a menu script that goes into a loop if the script inadvertantly runs in background mode. I suspect the connection is being lost in a citrix session.

I want to put in a code check that will terminate the script if it is not currently interactive.

Perhaps the following will be sufficient?
BASENAME=`/usr/bin/basename $0`
ps -ef | grep " $$ " | grep $BASENAME | grep -v "ps -ef" | grep -v grep | grep "?"


jack...

[Chris Wilshaw · Accepted solution]

Quick and dirty test which should work.

if [ `tty | grep not | wc -l` = 1 ];
then
export BACKGROUND=YES
else
export BACKGROUND=NO
fi

This checks to see if there's a controlling tty for the job - if not, assume that it's running in the background (eg. via cron).

the $BACKGROUND parameter can then be used to exit/continue.

[Rodney Hills]

You could see if stderr is assigned to a terminal.

if [[ -t 3 ]] ; then
echo "I am running in interactive"
else
echo "I am running in batch"
fi

-- Rod Hills

[MANOJ SRIVASTAVA]

Hi Jack

This will be good as you are trying to check on the current terminal session and then of course

export A=`ps -ef | grep " $$ " | grep $BASENAME | grep -v "ps -ef" | grep -v grep | grep "?" `
kill -9 $A


Manoj Srivastava

[Ceesjan van Hattum]

I'm not sure, but if you start a script within a shell as a background process, the shell will fork and run the script in a child-shell.

PID=A PPID=B -sh
PID=C PPID=A -sh
PID=D PPID=C $BASENAME

So i should be possible to look whether or not the shell running the program was forked or not. In case the shell was forked, you program is running in backupground.

Hope it will help you.
Regards,
Ceesjan

[Jack C. Mahaffey]

Really good solutions. Thanks... jack...