#/bin/bash
# roman.sh
#
#	Function
#
	num2roman() { # NUM
	# Returns NUM in roman letters
	#
		input=$1	# input num
		output=""	# Clear output string
		len=${#input}	# Initial length to count down
		
		roman_val() { # NUM one five ten
		# This sub does the basic 'roman' algorythm
		#
			N=$1
			one=$2
			five=$3
			ten=$4
			out=""
			
			case $N in
			0)	out+=""	;;
			[123])	while [[ $N -gt 0 ]]
				do	out+="$one"
					N=$(($N-1))
				done
				;;
			4)	out+="$one$five"	;;
			5)	out+="$five"	;;
			[678])	out+="$five"
				N=$(($N-5))
				while [[ $N -gt 0 ]]
				do	out+="$one"
					N=$(($N-1))
				done
				;;
			9)	while [[ $N -lt 10 ]]
				do	out+="$one"
					N=$(($N+1))
				done
				out+="$ten"
				;;
			esac
			echo $out
		}
		
		while [[ $len -gt 0  ]]
		do	# There are letters to add
			num=${input:0:1}
			# Do action according position
			case $len in
			1)	# 1
				output+="$(roman_val $num I V X)"
				;;
			2)	# 10
				output+="$(roman_val $num X L C)"
				;;
			3)	# 100
				output+="$(roman_val $num C D M)"
				;;
			*)	# 1000+
				# 10'000 gets a line above, 100'000 gets a line on the left.. how to?
				num=${input:0:(-3)}
				while [[ $num -gt 0 ]]
				do	output+="M"
					num=$(($num-1))
				done
				
				;;
			esac
			input=${input:1} ; len=${#input}
		done
		echo $output
	}
#
#	Call it
#
	num2roman $1

+ ~ $ for N in 1 4 5 6 8 9 10 13 42 99 123 256 1024 2048 3999;do ./roman.sh $N;done

I
IV
V
VI
VIII
IX
X
XIII
XLII
XCIX
CXXIII
CCLVI
MXXIV
MMXLVIII
MMMCMXCIX