topic scripting a background process in Operating System - Linux

scripting a background process

Timothy P. Jackson — Thu, 28 Jun 2007 19:17:54 GMT

Hello everyone,

I am writing a script that works perfectly in the fore ground. The script starts a background process that monitors the parent process so that it knows when it is done. The background process writes time updates to the screen so that the user knows that the parent process is still running. The problem I am having is that if I try to run the parent script in the background I get a SIGTTOU message and the script stops until I bring it back into the fore ground.

I know the problem is with the script trying to write to the crontroling tty and it can't but I am not sure if there is a way around it. Does any one have any ideas?

I hope this all made sense!!

Thanks,
Tim

Re: scripting a background process

A. Clay Stephenson — Thu, 28 Jun 2007 20:12:18 GMT

Add a trap to the writing process telling it to ignore SIGTTOU.

bear in mind that there is another better way to determine if a background process is still running.

child_proc.sh &
CHILD_PID=${!}

Now periodically do
kill -0 ${CHILD_PID}
CHILD_STAT=${?}
if [[ ${CHILD_STAT} -eq 0 ]]
then
echo "The kid is still running"
fi

Re: scripting a background process

Timothy P. Jackson — Thu, 28 Jun 2007 20:15:40 GMT

Thanks Clay!

This makes total sense and probably more efficient.

Tim