matrix-style-cascading-screensaver-in-bash

matrix-screensaver.sh

#!/bin/bash
# free time plus a need to build a screensaver in bash, enjoy the cascade.
# ps. the key to this is the "eval" function.
# - gary

# clear the screen and hide the cursor
echo -e "\033[2J\033[?25l"

# get the number of lines and columns of the terminal
R=$(tput lines)
C=$(tput cols)
R=$((R - 1))  # decrease R by 1 for zero-based indexing

# dame to display
name="Gary"
name_length=${#name}

while true; do
    (
        # shorthand for echo and sleep
        e='echo -e'
        s='sleep'

        j=$((RANDOM % C))
        d=$((RANDOM % R))

        # display characters
        for i in $(eval echo {1..$R}); do
            if ((RANDOM % 10 == 0)); then
                #c=${name:$((RANDOM % name_length)):1}
		c=$name
            else
                c=$(printf '\\\\0%o' $((RANDOM % 57 + 33)))
            fi

	    # print the character in green then in white at each position(matrix style)
            eval $e "\"\033[$((i-1));${j}H\033[32m$c\033[$i;${j}H\033[37m$c\""

            eval $s 0.1

            if [ $i -ge $d ]; then
                eval $e "\"\033[$((i-d));${j}H \""
            fi
        done

        for i in $(eval echo {$((i-d))..$R}); do
            eval $e "\"\033[$i;${j}f \""
            eval $s 0.1
        done
    ) &
    sleep 0.05
done

# does this even work?
trap 'echo -e "\033[?25h"; clear; exit' SIGINT