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Re: SIGSTOP and bash's time built-in

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On Fri, 30 Oct 2015 14:00:10 -0400
Chet Ramey <chet.ramey@case.edu> wrote:
 
> On 10/30/15 12:50 PM, Mike Frysinger wrote:
> > On 26 Oct 2015 16:59, Stefan Tauner wrote:
> >> I was creating some exercises for my students when I noticed very
> >> strange behavior of the time built-in when sending SIGSTOP to a timed
> >> command interactively (via ^Z):
> > 
> > you could always install the dedicated time program and then do:
> > $ /usr/bin/time sleep 5
> > 
> > that'll handle ^Z and such
> 
> It's probably already installed, and \time will work to invoke it.

Yes of course and this is the workaround I suggested to my students,
but this is still a major bug IMHO. The output of time(1) is defined in
POSIX as "[…]time between invocation of utility and its termination."
(http://pubs.opengroup.org/onlinepubs/9699919799/utilities/time.html).
I am not aware of any exceptions...(?) so the bash built-in clearly
breaks this major aspect of the defined behavior.

I'd rather see the built-in removed than continuing to provide a known
bad implementation... but I guess that opinion/expectation is rather
far-fetched :)

> If you look at time_command(), you'll see that it prints timing statistics
> when execute_command_internal() returns.  However, that will return when
> the foreground job changes state (since that indicates that the shell
> should read and execute another command).  The shell isn't structured well
> to discover at this point that the most recent job has been suspended, nor
> are there enough hooks to print timing statistics when the command is
> restarted and finally completes.

Thanks four that explanation. It does not sound too encouraging thus
I really hope someone will beat me to fixing it :)

KR
-- 
Dipl.-Ing. Stefan Tauner
Research and Development
Embedded Systems Department

University of Applied Sciences Technikum Wien
Hoechstaedtplatz 6, 1200 Vienna, Austria
T: +43 1 3334077-316
E: stefan.tauner@technikum-wien.at
I: embsys.technikum-wien.at
I: www.technikum-wien.at

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Re: SIGSTOP and bash's time built-in Stefan Tauner <tauner@technikum-wien.at> - 2015-10-30 20:34 +0100

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