Why (or when) is Rscript (or littler) better than R CMD BATCH?
batch-file, cmd, cron, r, rscript
Solution
`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.
Problem
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`?