Originally posted by: SystemAdmin

Is there an easy idiom for imposing a timeout on
a section of shell script?

I have a list of commands in a /bin/sh script
do-something
do-something-else
do-some-more

The do-something-else (e.g. db2) may wait indefinitely
for input.

What I want to happen is:
1. start a countdown timer for T seconds
2. begin executing do-something, do-something-else, ...
3. if the timer reaches 0
send SIGHUP to the execution in step 2
4. if execution in step 2 completes
cleanly dispose of the timer.

How can a timeout limit like the above
be done cleanly within a shell script?

I vaguely remember using some combination of fork(1),
exec(1), ??? to do this in the past.

TIA,

#AIX-Forum

Originally posted by: SystemAdmin

This is additional data that may narrow the question.
It can be safely ignored, if there is a simpler idiom.

Letting my swiss-cheese memory direct my fingers,
I started piecing together a test case.

It works, except that:
even when the task is "COMPLETED" (e.g. 5 sec)
in less than the timeout period (e.g. 30 sec),
the script is not "finished" until after the sleep completes
(30 sec rather than desired 5 sec).

I vaguely remember wait(1) being involved.

To use the example, execute it twice,
once with TIMEOUT and TASKTIME set in favor of TIMEOUT
and once in favor of TASKTIME.

• example code --

TIMEOUT=30
TASKTIME=5

1. Start the task that may take too long

START=$(date)
(
while test 0 -lt $TASKTIME; do
echo "task in progress"; sleep 1
let "TASKTIME=TASKTIME-1"
done
echo "COMPLETED"
) &
CHILD=$!

1. Start a watchdog

sleep $TIMEOUT
if kill -HUP $CHILD 2>/dev/null; then echo "TIMEOUT"; fi

echo "finished"

• example code --

TIA,
#AIX-Forum

Originally posted by: SystemAdmin

The following will start a timer and try to execute a list.
If the timer expires, the list will receive an HUP signal.
If the list completes, the timer will receive an HUP signal.
The lines after 'wait' will be executed,
after the list completes or the timer expires,
whichever comes first.

---

idiom

---

...
(tasks;that;might;take;too;long) &
TIMED=$!; (sleep $TIMEOUT; kill -HUP $TIMED) &
TIMER=$!; wait $TIMED; kill -HUP $TIMER
...

---

idiom

---

---

example

---

1. Author: drb
2. Forum: IBM developerWorks>AIX and UNIX>AIX - technical

1. Execute with and without timeout

for TASKTIME in 5 15
do
TIMEOUT=10

# Start the task that may take too much time
(
while test 0 -lt $TASKTIME
do
echo "$TASKTIME"; sleep 1
let "TASKTIME=TASKTIME-1"
done
echo "COMPLETED"
) &
TIMED=$!

# Start a timer
(
sleep $TIMEOUT
if kill -HUP $TIMED 2> /dev/null; then echo "TIMEOUT"; fi
) &
TIMER=$!

# Wait for completion (or timeout)
wait $TIMED 2> /dev/null
kill -HUP $TIMER 2> /dev/null

# Do other things
if test $TASKTIME -lt $TIMEOUT
then
echo "The tasks should have completed."
else
echo "The timer should have expired."
fi
done

---

example

---

Archiving,
#AIX-Forum