[Rd] Bug when calling system/system2 (and request for Bugzilla account)

luke-tier@ey m@ili@g off uiow@@edu luke-tier@ey m@ili@g off uiow@@edu
Fri Sep 14 17:39:26 CEST 2018

I can't reproduce this. Can you be more precise: exactly where are you
putting the system2 call and exactly where are you sending the
interrupt signal with ^C?



On Fri, 14 Sep 2018, Emil Bode wrote:

> Hi all,
> I found some strange behaviour, which I think is a bug. Could someone make an account for me on Bugzilla or pass on my report?
> The problem:
> When pressing Ctrl-C when a file is sourced in R, run from Terminal (macOS), sometimes the entire session is ended right away, while I just want to stop the script. This is the case when I press Ctrl-C while some functions are running that don’t catch the interrupt. However, the behaviour is different whether I’m in a clean session (in which case some time is allowed to pass, so that when the function returns the script can be interrupted), or whether I have called base::system() or system2() with timeout other than 0.
> Reproducible example:
> cat('Start non-interruptable functions\n')
> sample_a <- sample(1:1e7)
> sample_b <- sample(1:2e7)
> matching <- match(sample_a, sample_b)
> cat('Finished\n')
> Sys.sleep(10)
> Observed behaviour:
> In a clean session, when I hit Ctrl-C during the execution of match, there is a delay, and as soon as Sys.sleep() is invoked, the script is interrupted, I get back my R “>”-prompt (unless options(error=…) is set)
> But If I add the line system2("ls", timeout = 5), or something similar, when I try to break during the first part of the script, my Rsession ends, I get thrown back to my terminal-prompt.
> Desired behaviour:
> The best setup would probably be if Ctrl-C would always try to break from the sourced file, and only if that doesn’t success in n seconds, break the rsession altogether, ideally with a customizable option. But maybe that’s too hard, so maybe the most pragmatic would be to have 2 hotkeys: one to break from a hanging/broken rsession, and one to gently try to break from a script. But at least I think it should be:
> Expected behaviour:
> Consistent behaviour for Ctrl-C: either trying to break the script, or end the session altogether.
> Some observations:
>  *   I can still break cleanly during the Sys.sleep(). But for larger scripts, it is largely a matter of luck if I hit Ctrl-C during the right moment.
>  *   I don’t notice any difference between using system or system2, or any of the arguments other than timeout provided
>  *   I don’t notice any difference whether the timeout is actually exhausted or not.
>  *   Later calls to system/system2 don’t change anything (i.e. later calling system(…, timeout=0) does not revert back to the old situation)
> My setup:
> R 3.5.1 (Feather Spray), run with –vanilla option
> GNU bash, version 3.2.57(1)-release (x86_64-apple-darwin17)
> macOS High Sierra 10.13.6
> Best regards,
> Emil Bode
> Data-analyst
> +31 6 43 83 89 33
> emil.bode using dans.knaw.nl<mailto:emil.bode using dans.knaw.nl>
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Luke Tierney
Ralph E. Wareham Professor of Mathematical Sciences
University of Iowa                  Phone:             319-335-3386
Department of Statistics and        Fax:               319-335-3017
    Actuarial Science
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Iowa City, IA 52242                 WWW:  http://www.stat.uiowa.edu

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