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# optparse: Command line optional argument parser
[](https://cran.r-project.org/package=optparse)
[](https://github.com/trevorld/r-optparse/actions)
[](https://app.codecov.io/github/trevorld/r-optparse?branch=master)
[](https://cran.r-project.org/package=optparse)
<img src="man/figures/logo.png" align="right" width="200px" alt="optparse hex sticker">
A pure R language command line parser inspired by Python's 'optparse'
library to be used with Rscript to write "\#!" shebang scripts that
accept short and long flag/options.
To install the last version released on CRAN use the following command:
install.packages("optparse")
To install the development version use the following command:
install.packages("remotes")
remotes::install_github("trevorld/r-optparse")
## dependencies
This package depends on the R package `getopt`.
To run the unit tests you will need the suggested R package `testthat`
and in order to build the vignette you will need the suggested R package
`knitr` which in turn probably requires the system tool `pandoc`:
sudo apt install pandoc
## examples
A simple example:
library("optparse")
parser <- OptionParser()
parser <- add_option(parser, c("-v", "--verbose"), action="store_true",
default=TRUE, help="Print extra output [default]")
parser <- add_option(parser, c("-q", "--quietly"), action="store_false",
dest="verbose", help="Print little output")
parser <- add_option(parser, c("-c", "--count"), type="integer", default=5,
help="Number of random normals to generate [default %default]",
metavar="number")
parse_args(parser, args = c("--quietly", "--count=15"))
## $help
## [1] FALSE
##
## $verbose
## [1] FALSE
##
## $count
## [1] 15
Note that the `args` argument of `parse_args` default is
`commandArgs(trailing=TRUE)` so it typically doesn't need to be
explicitly set if writing an Rscript.
One can also equivalently make options in a list:
library("optparse")
option_list <- list(
make_option(c("-v", "--verbose"), action="store_true", default=TRUE,
help="Print extra output [default]"),
make_option(c("-q", "--quietly"), action="store_false",
dest="verbose", help="Print little output"),
make_option(c("-c", "--count"), type="integer", default=5,
help="Number of random normals to generate [default %default]",
metavar="number")
)
parse_args(OptionParser(option_list=option_list), args = c("--verbose", "--count=11"))
## $verbose
## [1] TRUE
##
## $count
## [1] 11
##
## $help
## [1] FALSE
`optparse` automatically creates a help option:
parse_args(parser, args = c("--help"))
Usage: %prog [options]
Options:
-h, --help
Show this help message and exit
-v, --verbose
Print extra output [default]
-q, --quietly
Print little output
-c NUMBER, --count=NUMBER
Number of random normals to generate [default 5]
Error in parse_args(parser, args = c("--help")) : help requested
Note by default when `optparse::parse_args` sees a `--help` flag it will
first print out a usage message and then either throw an error in
interactive use or call `quit` in non-interactive use (i.e. when used
within an Rscript called by a shell). To disable the error/quit set the
argument `print_help_and_exit` to `FALSE` in `parse_args` and to simply
print out the usage string one can also use the function `print_usage`.
`optparse` has limited positional argument support, other command-line
parsers for R such as `argparse` have richer positional argument
support:
parse_args(parser, args = c("-vc", "25", "75", "22"), positional_arguments = TRUE)
## $options
## $options$help
## [1] FALSE
##
## $options$verbose
## [1] TRUE
##
## $options$count
## [1] 25
##
##
## $args
## [1] "75" "22"
The function `parse_args2` wraps `parse_args` while setting
`positional_arguments=TRUE` and `convert_hyphens_to_underscores=TRUE`:
parse_args2(parser, args = c("-vc", "25", "75", "22"))
## $options
## $options$help
## [1] FALSE
##
## $options$verbose
## [1] TRUE
##
## $options$count
## [1] 25
##
##
## $args
## [1] "75" "22"
|
