[Rd] system command
Prof Brian Ripley
ripley@stats.ox.ac.uk
Fri, 9 Feb 2001 14:28:58 +0000 (GMT)
On Fri, 9 Feb 2001, Erich Neuwirth wrote:
> i am using
> system
> to call the external program csound.
> csound does some output to stdout and some to stderr
> system handles this differently on the different platforms.
>
> on unix (i have solaris, but as far as i know it is the same on linux)
> system("csound",intern=TRUE) redirects stdin into an R object,
> by still outputs stdout to the R window.
I *think* you mean redirect stdout, and sends stderr to the terminal
running R.
> system("csound",intern=FALSE) (equivalent to system("csound"))
> stdout and stderr go into the R window
>
> Rterm
> on win95
> system("csound",intern=TRUE) redirects stdin and stderr into an R object
Redirects stdout and stderr to the terminal running R?
> system("csound",intern=FALSE) (equivalent to system("csound"))
> outputs everything
>
> Rterm
> on win2k
> system("csound",intern=TRUE) redirects stdin and stderr into an R object
> system("csound",intern=FALSE) (equivalent to system("csound"))
> outputs everything
> EXCEPT
> once
> system("csound",intern=TRUE) has been done
> and later one tries
> system("csound",intern=FALSE)
> stderr is lost completely.
> going back to
> system("csound",intern=TRUE)
> redirects stderr again into the R object,
> but stderr does not go to the screen any more
> after intern=TRUE has been used once.
>
>
> so we seem to have to problems:
> 1) different behavior of system on unix and win32k
They are documented to be different! Whether stdout and stderr are
different is OS-specific. In particular, Windows consoles have no concept
of stdout.
> 2) problems with system and redirection on win32k.
A bug, almost certainly in Windows 2000 since this works as documented
under NT. Guido?
But, the essence is that you cannot reasonably expect to use stderr from
a program run by a system() commands, and that applies to, say, Perl
as much as to R.
--
Brian D. Ripley, ripley@stats.ox.ac.uk
Professor of Applied Statistics, http://www.stats.ox.ac.uk/~ripley/
University of Oxford, Tel: +44 1865 272861 (self)
1 South Parks Road, +44 1865 272860 (secr)
Oxford OX1 3TG, UK Fax: +44 1865 272595
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