exec/display_file.R

In optparse: Command Line Option Parser

#!/usr/bin/env Rscript
# Copyright 2010-2013 Trevor L Davis <trevor.l.davis@gmail.com>
# Copyright 2013 Kirill Müller
#
#  This file is free software: you may copy, redistribute and/or modify it
#  under the terms of the GNU General Public License as published by the
#  Free Software Foundation, either version 2 of the License, or (at your
#  option) any later version.
#
#  This file is distributed in the hope that it will be useful, but
#  WITHOUT ANY WARRANTY; without even the implied warranty of
#  MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
#  General Public License for more details.
#
#  You should have received a copy of the GNU General Public License
#  along with this program.  If not, see <http://www.gnu.org/licenses/>.
suppressPackageStartupMessages(library("optparse"))

parser <- OptionParser(usage = "%prog [options] file")
parser <- add_option(
	parser,
	c("-n", "--add_numbers"),
	action = "store_true",
	default = FALSE,
	help = "Print line number at the beginning of each line [default]"
)

arguments <- parse_args(parser, positional_arguments = 1)
opt <- arguments$options
file <- arguments$args

if (!file.exists(file)) {
	stop(sprintf("Specified file ( %s ) does not exist", file))
} else {
	file_text <- readLines(file)
}

if (opt$add_numbers) {
	cat(paste(seq_along(file_text), file_text), sep = "\n")
} else {
	cat(file_text, sep = "\n")
}