The r binary provides a convenient and powerful front-end.
By embedding R, it permits four distinct ways to leverage the power of R at
the shell prompt: scripting, filename execution, piping and direct expression
evaluation.
Common with other shell tools and programs, r returns its exit code where
a value of zero indicates success.
Jeff Horner and Dirk Eddelbuettel wrote littler from 2006 to today, with
contributions from several others.
Dirk Eddelbuettel edd@debian.org is the maintainer.
The r front-end was written with four distinct usage modes in mind.
First, it allow to write so-called ‘shebang’ scripts starting with
#!/usr/bin/env r. These ‘shebang’ scripts are
perfectly suited for automation and execution via e.g. via cron.
Second, we can use r somefile.R to quickly execute the name R source file.
This is useful as r is both easy to type---and quicker to start that either
R itself, or its scripting tool Rscript, while still loading the
methods package.
Third, r can be used in ‘pipes’ which are very common in Unix. A
simple and trivial example is echo 'cat(2+2)' | r illustrating that the
standard output of one program can be used as the standard input of another
program.
Fourth, r can be used as a calculator by supplying expressions after the
-e or --eval options.