Carlos Cinelli Carlos Cinelli - 2 months ago 11
R Question

Why (or when) is Rscript (or littler) better than R CMD BATCH?

I am automating some webscraping with

R
in
cron
and sometimes I use
R CMD BATCH
and sometimes I use
Rscript
.

To decide which one to use I mainly focus if I want the
.Rout
file or not.

But reading the answers to some questions here in SO (like this or this) it seems that
Rscript
is preferred to
R CMD BATCH
.

So my questions are:


  • Besides the fact that the syntax is a little different and
    R CMD BATCH
    saves an
    .Rout
    file while
    Rscript
    does not, what are the main differences between the two of them?

  • When should I prefer one over another? More specifically, in the
    cron
    job above mentioned, is one of them preferred?

  • I have not used yet
    littler
    , how is it different from both
    Rscript
    and
    R CMD BATCH
    ?


Answer

R CMD BATCH is all we had years ago. It makes i/o very hard and leaves files behind.

Things got better, first with littler and then too with Rscript. Both can be used for 'shebang' lines such as

 #!/usr/bin/r

 #!/usr/bin/Rscript

and both can be used with packages like getopt and optparse --- allowing you to write proper R scripts that can act as commands. If have dozens of them, starting with simple ones like this which I can call as install.r pkga pkgb pkgc and which will install all three and their dependencies) for me from the command-line without hogging the R prompt:

#!/usr/bin/env r       
#
# a simple example to install one or more packages 

if (is.null(argv) | length(argv)<1) {
  cat("Usage: installr.r pkg1 [pkg2 pkg3 ...]\n")
  q()
}

## adjust as necessary, see help('download.packages') 
repos <- "http://cran.rstudio.com"

## this makes sense on Debian where no packages touch /usr/local 
lib.loc <- "/usr/local/lib/R/site-library"

install.packages(argv, lib.loc, repos)

And just like Karl, I have cronjobs calling similar R scripts.

Edit on 2015-11-04: As of last week, littler is now also on CRAN.