topic Re: How to know when a background task is complete? in Operating System - HP-UX

How to know when a background task is complete?

John Chaff — Fri, 26 Mar 2004 17:08:34 GMT

Hello,

Inside a script, I start a another script in the background so I can continue processing. Is there a way besides ps to find out when this command has finished?

Thanks,
John

Re: How to know when a background task is complete?

A. Clay Stephenson — Fri, 26 Mar 2004 17:12:21 GMT

This is pretty much Duck Soup.

mybackground.sh &
CHILDPID=${!}

Now all you have to do is periodically:
kill -0 ${CHILDPID}
STAT=${?}
if [[ ${STAT} -eq 0 ]]
then
echo "Kid is still going"
else
echo "Kid is dead"
fi

Man 1 kill for details.

Re: How to know when a background task is complete?

A. Clay Stephenson — Fri, 26 Mar 2004 17:15:09 GMT

Plan B.

Have the child send a signal via kill to the parent process (using ${PPID}) just before the child terminates. The parent script, in turn, has a trap for the chosen signal. This is probably a better method because you no longer have to loop inside the parent checking on the status of the child.

Re: How to know when a background task is complete?

Sundar_7 — Fri, 26 Mar 2004 17:16:55 GMT

Hi John,

Alternatively, at some point of time, if you have to just wait on the background process you started to end, then you can use the wait command.

man wait for details

Sundar.

Re: How to know when a background task is complete?

John Chaff — Fri, 26 Mar 2004 17:33:13 GMT

Thanks. The kill -0 was just what I needed.

John