[R] writing R shell scripts?
dchandra at ics.uci.edu
Thu Jan 25 20:22:30 CET 2007
> > Hi All,
> > Another newbie question. I want to write an R script that takes
> > argument from command line and runs and produces output to stdin.
> You will find that difficult: did you mean stdout?
My mistake -- I meant stdout :).
> > For example if there is file foo.R with following in it.
> > args = commandArgs()
> > print(args)
> > then, when I run it like
> > $ R foo.R hello
> > it should print 'hello' on the terminal.
> > I searched the mainling list and found a very old post that said said
> Please give an exact reference so we know what you are referring to.
> This is not what is usually meant by 'R shell scripts' (it is an R script,
> not a shell script).
> > that this feature will be implemented soon. I am expecting this has
> > already been implemented by now.
> That is not what commandArgs() is documented to do so you will need to do
> something slightly different. But in the development version of R you can
> come very close:
> gannet% cat foo.R
> args <- commandArgs(TRUE)
> gannet% ~/R/R-devel/bin/Rscript foo.R hello
>  "hello"
> and in any recent version of R
> gannet% cat foo2.R
> args <- commandArgs()
> m <- match("--args", args)
> gannet% R --slave --args hello < foo2.R
>  "hello"
> If you have a platform and build of R for which it works, there is also
> littler (http://biostat.mc.vanderbilt.edu/twiki/bin/view/Main/LittleR),
> but beware that are restrictions not stated on that page (such as the need
> for R built as a shared library, which is not the default).
My apologies for being sketchy in my example: I was hoping to
elucidate my problem without too many details.
I was looking #! capabilites for running my scripts with different
arguments from my shell.
Your response was helpful, and one of the three alternatives that you
pointed to should solve my problem.
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