how to set time-outs for commands in a script

[Jdamian]

Hi

Sometimes I need to set a time-out for a command line in a critical script.

is there any trick to achieve that ?

[Oviwan]

Hey

check "man sleep" and "man wait"

Regards

[Ralph Grothe]

I don't think sleep and wait is what you want.
sleep would simply block the execution of the next command for the number of seconds passed to sleep, while wait would block until all backgrounded, or that whose PID was passed to wait, have finished.
In Perl scripts one usually sets up a signal handler for SIGALRM (at least one could do this with a shell trap) in an eval block and triggers the alarm() syscall.
I wonder if the shell offers a similar scriptable solution, or if one would have to resort to a C or Perl "plugin"?

[James R. Ferguson]

Hi Oscar:

In a shell script you can use 'line -t' like:

# REPLY=`line -t 10`
# [ -z "${REPLY}" ] && echo "You didn't enter anything!"

The argument to '-t' is an integer number of seconds to wait on a read of data before timing out.

Regards!

...JRF...

[Steven Schweda]

What's your "command line"?

There are always many details to be worked
out, but did you mean something like this?

urtx> cat ./trap_test.sh
#!/bin/sh

# Establish a no-op SIGCHLD handler.
trap ":" 20

# Display date-time, and set the timer.
date
sleep 10 &

# Begin the time-uncertain command sequence.
echo 'question? \c'
read ans
echo "ans: >${ans}<"

# Display date-time after the time-uncertain command sequence.
date

urtx> ./trap_test.sh
Thu Apr 19 08:36:39 CDT 2007
question? a
ans: >a<
Thu Apr 19 08:36:40 CDT 2007

urtx> ./trap_test.sh
Thu Apr 19 08:36:50 CDT 2007
question?
ans: ><
Thu Apr 19 08:37:00 CDT 2007

[James R. Ferguson]

Hi Oscar:

Ping. Perhaps you will evaluate the latest responses.

Regards!

...JRF...

[Bill Hassell · Accepted solution]

You did not specify whether the timeout is related to waitning for an interactive response from a user, or to watch certain processes called by the script and kill them if it runs too long. There is no script-wide timeout. For a process that might take too long, you put the process into the background, then watch the process to see if it completes within a reasonable length of time, and if not, kill the process. This is not simple scripting but can be done.

[Jdamian]

.