colorcount

#!/usr/bin/env bash

# colorcount - Count color capacity of terminal
trap 'tput sgr0' exit  # Clean up even if user hits ^C

setfg(){ printf '\e[38;5;%dm' $1;}
setbg(){ printf '\e[48;5;%dm' $1;}
showcolors(){
	# Given an integer, display that many colors
	for ((i=0; i<$1; i++))
	do
		printf '%4d ' $i
		setbg $i
		tput el
		tput sgr0
		echo
	done
	tput sgr0 el
}

# First, test if terminal supports OSC 4 at all.
printf '\e]4;%d;?\a' 0
read -d $'\a' -s -t 0.1 </dev/tty
if [[ -z $REPLY ]]
then # OSC 4 not supported, so we'll fall back to terminfo
	max=$(tput colors)
else # OSC 4 is supported, so use it for a binary search
	min=0 max=256
	while ((min+1 < max))
	do
		((i=(min+max)/2))
		printf '\e]4;%d;?\a' $i
		read -d $'\a' -s -t 0.1 </dev/tty
		[[ $REPLY ]] && min=$i || max=$i
	done
fi

# If -v is given, show all the colors
case ${1-none} in
none) echo $max ;;
-v) showcolors $max ;;
*) (($1>0)) && showcolors $1 || echo $max
esac #|less --raw-control-chars --QUIT-AT-EOF --no-init