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\encoding{latin1}
\name{parse_args}
\alias{parse_args}
\title{Parse command line options.}
\usage{
parse_args(object,
args = commandArgs(trailingOnly = TRUE),
print_help_and_exit = TRUE,
positional_arguments = FALSE)
}
\arguments{
\item{object}{An \code{OptionParser} instance.}
\item{args}{A character vector containing command line
options to be parsed. Default is everything after the
Rscript program in the command line. If
\code{positional_arguments} is not \code{FALSE} then
\code{parse_args} will look for positional arguments at
the end of this vector.}
\item{print_help_and_exit}{Whether \code{parse_args}
should call \code{print_help} to print out a usage
message and exit the program. Default is \code{TRUE}.}
\item{positional_arguments}{Number of \emph{positional}
arguments. A numeric denoting the exact number of
supported arguments, or a numeric vector of length two
denoting the minimum and maximum number of arguments
(\code{Inf} for no limit). The value \code{TRUE} is
equivalent to \code{c(0, Inf)}. The default \code{FALSE}
is supported for backward compatibility only, as it
alters the format of the return value.}
}
\value{
Returns a list with field \code{options} containing our
option values as well as another field \code{args} which
contains a vector of positional arguments. For backward
compatibility, if and only if \code{positional_arguments}
is \code{FALSE}, returns a list containing option values.
}
\description{
\code{parse_args} parses command line options using an
\code{OptionParser} instance for guidance.
}
\section{Acknowledgement}{
A big thanks to Steve Lianoglou for a bug report and
patch; Juan Carlos \enc{Borrás}{Borras} for a bug report;
Jim Nikelski for a bug report and patch; Ino de Brujin
and Benjamin Tyner for a bug report; Jonas Zimmermann for
bug report; Miroslav Posta for bug reports; Stefan
Seemayer for bug report and patch; Kirill
\enc{Müller}{Muller} for patches.
}
\examples{
# example from vignette
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"),
make_option("--generator", default="rnorm",
help = "Function to generate random deviates [default \\"\%default\\"]"),
make_option("--mean", default=0,
help="Mean if generator == \\"rnorm\\" [default \%default]"),
make_option("--sd", default=1, metavar="standard deviation",
help="Standard deviation if generator == \\"rnorm\\" [default \%default]")
)
parse_args(OptionParser(option_list = option_list), args = c("--sd=3", "--quietly"))
# example from vignette using positional arguments
option_list2 <- list(
make_option(c("-n", "--add_numbers"), action="store_true", default=FALSE,
help="Print line number at the beginning of each line [default]")
)
parser <- OptionParser(usage = "\%prog [options] file", option_list=option_list2)
parse_args(parser, args = c("--add_numbers", "example.txt"), positional_arguments = TRUE)
parse_args(parser, args = c("-add_numbers", "example.txt"), positional_arguments = TRUE)
}
\author{
Trevor Davis.
}
\references{
Python's \code{optparse} library, which inspired this
package, is described here:
\url{http://docs.python.org/library/optparse.html}
}
\seealso{
\code{\link{OptionParser}} \code{\link{print_help}}
}
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