Re: New util suggestion: timeout

[Philip Rowlands]

On Mon, 28 Jun 2004, Paul Jarc wrote:

>>> How would you limit wall-clock time?  Schedule SIGALRM with
>>> setitimer and then exec the given command?
>>
>> I've long used a command of my own called 'alarm' that just does that.
>> However, this strategy doesn't always work well if the command has
>> subprocesses, since the signal is sent only to the exec'ed process.
>
>It also fails if the command uses setitimer itself.  That could be
>handled by forking and having the parent send SIGTERM to the child
>when it gets its own SIGALRM.  To handle the child processes, a new
>process group could be created, but that might interfere with other
>things.

Yes, keep the parent hanging around to handle the killing, particularly
because you might want a two-stage kill (SIGTERM, sleep(5), SIGKILL).

Process group helps when there might be sub-sub-processes, but as you
say that has the potential to interfere with things which don't expect
it, so perhaps make it a command-line parameter.

So far then, I've got as potential command line args:
- Seconds to sleep until first signal
- Which signal to deliver at timeout #1
- Seconds to sleep until second signal (KILL)
- Optionally create process group and kill all children
- Exit status for the timeout condition

The most common use I've got right now (and this is what prompted me to
suggest it in the first place) is:
$ timeout 10 ssh otherhost 'some random command'


Cheers,
Phil