How to know when a background task is complete?

[John Chaff]

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

[A. Clay Stephenson · Accepted solution]

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.

[A. Clay Stephenson]

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.

[Sundar_7]

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.

[John Chaff]

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

John