#!/bin/bash
# copyright 2007 Gilbert Ashley <amigo@ibiblio.org>
# BashTrix tail is an implementation of the 'rev' command
# written in pure shell. rev takes no options.
VERSION=0.1

# show program usage
show_usage() {
echo
echo "Usage: ${0##/*} [FILE]..."
echo "  or: (cat|echo) | ${0##/*} [FILE]... "
echo "Reverse lines of a file."
echo "The rev utility copies the specified files to the standard output,"
echo "reversing the order of characters in every line."
echo "With no FILE specified, standard input is read."
echo "      --help     display this help and exit"
echo "      --version  output version information and exit"
exit
}
show_version() {
echo ${0##/*}" (BashTrix) $VERSION"
echo "Copyright 2007 Gilbert Ashley <amigo@ibiblio.org>"
echo "This is free software written in pure shell."
exit
}

# show usage if '-h' or  '--help' is the first argument or no argument is given
case $1 in
	"-h"|"--help") show_usage ;;
	"--version") show_version ;;
esac

for WORD in "$@" ; do
	case $WORD in
		-*)  true ;
			case $WORD in
				--help) show_usage ;;
				--version) show_version ;;
				--) READ_STDIN=1 ; shift ;;
			esac
		;;
	esac
done

if [[ $# -gt 0 ]] ; then
	while [[ $# -gt 0 ]] ; do
		FILE_NAME="$1"
		if [ ! -r "$1" ] ; then
			echo "Cannot find file $1" 1>&2
			exit 1
		else
			FILE_LINE_COUNT=0
			LINE=
			IFS=
			while read LINE ; do
				# add the curent line to the line counter
				(( FILE_LINE_COUNT++ ))
				OUTPUT_STRING=
				STRING=$LINE
				while [[ "$STRING" != "" ]] ; do
					OUTPUT_STRING=${STRING:0:1}$OUTPUT_STRING
					STRING=${STRING:1}
				done
				echo $OUTPUT_STRING
			done <"$1"
			
		fi
	# go to next FILE in $@
	shift
	done
else
	# piped input is presumed to be separated into lines already
	FILE_NAME="STDIN"
	# output the requested lines in the file
	FILE_LINE_COUNT=0
	LINE=
	IFS=
	while read LINE ; do
		# add the curent line to the line counter
		(( FILE_LINE_COUNT++ ))
		OUTPUT_STRING=
		STRING=$LINE
		while [[ "$STRING" != "" ]] ; do
			OUTPUT_STRING=${STRING:0:1}$OUTPUT_STRING
			STRING=${STRING:1}
		done
		echo $OUTPUT_STRING
		# go to next line in stdin
		shift
	done
fi