littler (version 0.3.2)

littler: Command-line and scripting front-end for R

Description

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.

Value

Common with other shell tools and programs, r returns its exit code where a value of zero indicates success.

Details

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.

Examples

# NOT RUN {
  
# }
# NOT RUN {
  #!/usr/bin/env r              ## for use in scripts

  other input | r               ## for use in pipes

  r somefile.R                  ## for running files

  r -e 'expr'                   ## for evaluating expressions

  r --help                      ## to show a quick synopsis
        
  
# }