numberCount.sh

#/bin/bash

# This script prints a range of numbers
# Usage: count [-r] [-b n] [-s n] stop
# -b gives the number to begin with (default: 0)
# -r reverses the count
# -s sets step size (default: 1)
# counting will stop at stop.

declare reverse=""
declare -i begin=0
declare -i step=1

while getopts "b:s:r" opt; do
	case $opt in
		r)
			reverse="yes"			
			;;
		b) 
			[[ ${OPTARG} =~ ^[0-9]+$ ]] || { echo "${OPTARG} is not a number" >&2; exit 1; }
			start="${OPTARG}"
			;;
		s)
			[[ ${OPTARG} =~ ^[0-9]+$ ]] || { echo "${OPTARG} is not a number" >&2; exit 1; }
			step="${OPTARG}"
			;;
		\?)
			exit 1
			;;
	esac
done

shift $(( OPTIND -1 ))

[[ $1 ]] || { echo "missing an argument" >&2; exit 1; }
declare end="$1"

if [[ ! $reverse ]]; then
	for (( i=start; i <= end; i+=step )); do
		echo $i
	done
else
	for (( i=end; i >= start; i-=step )); do
		echo $i
	done
fi

exit 0