R devel - Aug 2009 - exec subdirectory of a package

Hello,

WRE contains the following information about the "exec" subdirectory
of
a package :

"Subdirectory exec could contain additional executables the package 
needs, typically scripts for interpreters such as the shell, Perl, or 
Tcl. This mechanism is currently used only by a very few packages, and 
still experimental."

I think it would be useful to expand "very few". For example
"tcltk"
uses it.

But the real questions are;
- can this be used in conjunction with "R CMD", something like

$ R CMD execute package script parameters

The alternative used in a few packages (Rserve, Roxygen, ...) is to add 
a file in ${R_HOME}/bin, but I am not sure this works with binary builds 
of packages

- can the script be an R script, in that case would a shebang like this 
be enough :

#!/bin/env Rscript

definitely works on (at least my) linux

A very naive "execute" written in R follows.

Romain




#!/bin/env Rscript

args <- commandArgs(TRUE)
if( length(args) < 2 ){
         stop( "usage : R CMD execute package script [parameters]\n" )
}

package <- args[1]
script <- args[2]
scriptfile <- file.path( system.file( "exec", script, package =
package ) )
if( !file.exists( scriptfile ) ){
         stop( sprintf( "file not found: '%s' ", scriptfile  )
)
}

trail <- if( length(args) > 2 ) paste( tail( args, -2 ), sep = "
" ) else ""
cmd <- sprintf( '"%s" %s', scriptfile, trail )
system( cmd )



-- 
Romain Francois
Professional R Enthusiast
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Anyone ?

I guess I'll have to make a package that ships the execute script

Romain

On 08/05/2009 11:32 AM, Romain Francois wrote:
> Hello,
>
> WRE contains the following information about the "exec"
subdirectory of
> a package :
>
> "Subdirectory exec could contain additional executables the package
> needs, typically scripts for interpreters such as the shell, Perl, or
> Tcl. This mechanism is currently used only by a very few packages, and
> still experimental."
>
> I think it would be useful to expand "very few". For example
"tcltk"
> uses it.
>
> But the real questions are;
> - can this be used in conjunction with "R CMD", something like
>
> $ R CMD execute package script parameters
>
> The alternative used in a few packages (Rserve, Roxygen, ...) is to add
> a file in ${R_HOME}/bin, but I am not sure this works with binary builds
> of packages
>
> - can the script be an R script, in that case would a shebang like this
> be enough :
>
> #!/bin/env Rscript
>
> definitely works on (at least my) linux
>
> A very naive "execute" written in R follows.
>
> Romain
>
>
>
>
> #!/bin/env Rscript
>
> args<- commandArgs(TRUE)
> if( length(args)<  2 ){
>           stop( "usage : R CMD execute package script
[parameters]\n" )
> }
>
> package<- args[1]
> script<- args[2]
> scriptfile<- file.path( system.file( "exec", script, package =
package ) )
> if( !file.exists( scriptfile ) ){
>           stop( sprintf( "file not found: '%s' ",
scriptfile  ) )
> }
>
> trail<- if( length(args)>  2 ) paste( tail( args, -2 ), sep = "
" ) else ""
> cmd<- sprintf( '"%s" %s', scriptfile, trail )
> system( cmd )

-- 
Romain Francois
Professional R Enthusiast
+33(0) 6 28 91 30 30
http://romainfrancois.blog.free.fr
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