[R & Unix ..] system("test",...) gives funny results...
Peter Dalgaard BSA
p.dalgaard@biostat.ku.dk
10 Dec 1998 15:37:41 +0100
Martin Maechler <maechler@stat.math.ethz.ch> writes:
> [in an attempt to provide
>
> system.test <-
> function(...) { system(paste("test", ...)) == 0 }
> and then
> file.exists <-
> function(file){sapply(file, function(f)system.test("-e", f))}
>
> (which would provide S-plus [>= 4.x] compatibility)
> ]
>
> Look at this -- ``the horror'' to me :
>
> > (system("test -e /tmp"))
> sh: test: argument expected
> [1] 256
Happens to me on Solaris too, but *not* on Linux!
> Similar funny behavior (in tcsh; $version gives the tcsh version)
>
> In the shell
>
> sophie{maechler}639> echo $version
> tcsh 6.04.00 (Cornell) 93/07/03 (sun4) options 8b,nls,dl,al
>
> In R :
>
> > (system("echo $version"))
>
> [1] 0
>
> > {system("echo $version > /tmp/qq"); scan("/tmp/qq",what="")}
> Read 0 items
> character(0)
> >
Isn't this just because system() uses /bin/sh?
> {system("echo $USER > /tmp/qq"); scan("/tmp/qq",what="")}
Read 1 items
[1] "pd"
--
O__ ---- Peter Dalgaard Blegdamsvej 3
c/ /'_ --- Dept. of Biostatistics 2200 Cph. N
(*) \(*) -- University of Copenhagen Denmark Ph: (+45) 35327918
~~~~~~~~~~ - (p.dalgaard@biostat.ku.dk) FAX: (+45) 35327907
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