make shell script wait and send signal to recover it

esolve · 10-30-2012, 01:31 PM

when running a shell script
I want to make it wait for a signal somewhere inside the script,
like

Code:

function pause(){
   read -p "$*"
}
echo "start"
pause
echo "stop"

and then send a signal(when some conditions are satisfied) to make the script continue

is it possible or not?
thanks!

Habitual · 10-30-2012, 03:07 PM

I can't explain it b/c I haven't used it.
But here's some notes that may help.

Code:

...
#launching your program:
myprog&
#getting its id
id=$!
#killing it whenever you want
kill $id
...
#sleep for xx and restart script
do_stuff &
pid=$?
sleep xx
kill $pid
wait $pid

NOTE: These are 2 separate snippets.

David the H: should be along any minute...

Reuti · 11-01-2012, 12:36 PM

You mean POSIX signals? You can start one script in the background:

Code:

#!/bin/sh
echo "running PID=$$"
echo "start"
do_some_stuff_before
kill -stop $$
do_some_stuff_after
echo "stop"

Then it will stop and you can wake it up again by sending this process a signal to continue:

Code:

$ kill -cont 1234

by replacing the 1234 with the PID the first script output.

linosaurusroot · 11-02-2012, 10:13 PM

select() on file input is another way to get a program to stop executing until a condition is met. For anything at all complicated I recommend Perl over shell.

AnanthaP · 11-04-2012, 12:58 AM

Put the operative portion in a

Quote:

while <condition_is_not-satisfied>
do
...
...
done

loop