Prints the color codes for 256 colors

rainbow

#!/bin/bash

rainbow_base_colors() {
	for y in {0..1} ; do
		for x in {0..7} ; do
			c=$(( $x + (8 * $y) ))
			tput $t $c
			printf " %3s " $c
		done
		printf '\e[0m\n'
	done
	printf '\e[0m'
}

rainbow_ansii_colors() {
	a=16
	b=16
	c=16
	for z in {0..5} ; do
		for y in {0..5} ; do

			for x in {0..5} ; do
				tput $t $a
				printf " %3s " $a
				a=$(( $a + 1 ))
			done

			for x in {0..5} ; do
				tput $t $b
				printf " %3s " $b
				b=$(( $b + 36 ))
			done

			for x in {0..5} ; do
				tput $t $c
				printf " %3s " $c
				c=$(( $c + 1 ))
			done

			printf '\e[0m\n'
			b=$(( $b - 210 ))
			c=$(( $c + 30 ))
		done
		b=$(( $b - 35 ))
		c=$(( $c - 210 ))
		printf '\e[0m'
	done
}

rainbow_b_and_w_colors() {
	for y in {0..2} ; do
		for x in {0..7} ; do
			c=$(( 232 + $x + (8 * $y) ))
			tput $t $c
			printf " %3s " $c
		done
		printf '\e[0m\n'
	done
}

rainbow_help() {
	cat <<-HELP
		Usage: rainbow [ --background | --foreground | -b | -f ] [CODE...]
	HELP
}

main() {
	local args=() t=setab
	while (( $# )) ; do
		case "$1" in
			-h | --help) rainbow_help ; return ;;
			-b | --background) t=setab ; shift ;;
			-f | --foreground) t=setaf ; shift ;;
			*) args+=($1) ; shift ;;
		esac
	done

	if [ "${#args}" -eq 0 ] ; then
		rainbow_base_colors
		rainbow_ansii_colors
		rainbow_b_and_w_colors
		printf '\e[0m'
	else
		for c in ${args[@]} ; do
			tput $t $c
			printf " %3s " $c
		done
		printf '\e[0m\n'
	fi
}

main "$@"