cbg - a bash function (using AppleScript) to change the theme or background color of MacOS Terminal

cbg.sh

# Helpful resources:
# https://superuser.com/questions/1188772/mac-command-to-change-the-background-color-in-a-terminal
# https://apple.stackexchange.com/questions/348762/how-to-have-a-random-background-color-in-terminal-app
# https://stackoverflow.com/questions/8063228/how-do-i-check-if-a-variable-exists-in-a-list-in-bash
cbg(){
    local OCMD=""
    local RED=0; local GRN=0; local BLU=0;
    local THEMES="pro basic grass homebrew ocean" ## preset themes
    local HELPMSG; read -r -d '' HELPMSG <<EOF

cbg - a bash function (using AppleScript) to change the theme or background color of MacOS Terminal

Sample usage:

    cbg help                # print this help message

    cbg 42 255 120          # change background to rgb(42, 255, 120)

    cbg rand                # random background color

    cbg x                   # change background to preset of "x"
                            # Available presets: x l p r

    cbg grass               # use the "grass" Terminal theme
                            # Available themes:
                            #   $THEMES
---
EOF


    # if first argument matches a $THEMES name, then ignore other args, and change terminal theme
    if [[ "$THEMES" =~ (^|[[:space:]])${1}($|[[:space:]]) ]]; then
        OCMD="tell application \"Terminal\" to set current settings of window 1 to settings set \"$1\""

    # or do a random rgb value; note that we don't normalize to 255
    elif [[ "$1" == "rand" ]]; then
        RED=$((2000 + RANDOM % 21000))
        GRN=$((2000 + RANDOM % 21000))
        BLU=$((2000 + RANDOM % 21000))
    # otherwise, check if first arg is a rgb preset
    elif [[ "$1" == "x" ]]; then
        RED=11000; GRN=14000; BLU=20000  # 'x' is my fav
    elif [[ "$1" == "l" ]]; then
        RED=23000; GRN=16000; BLU=27000  # 'l' is some light lavender fun
    elif [[ "$1" == "p" ]]; then
        RED=9000;  GRN=20000; BLU=11000  # 'p' is python time
    elif [[ "$1" == "r" ]]; then
        RED=18000;  GRN=7000; BLU=8000   # 'r' is ruby time

    # if there are 0 arguments, or the 1st argument is unrecognized AND is non-numeric
    #     then don't change anything, but do print a help message
    elif [[ -z $1 || -n ${1//[0-9]/} || $1 -lt 0 ]]; then
        echo "$HELPMSG"
        return 0

    # else, interpret it as a list of RGB values, expressed as integers from 0 to 255
    else
        [[ "$1" -gt 0 && "$1" -le 255 ]] && RED=$(($1*65535/255)) || RED=0 ;
        [[ "$2" -gt 0 && "$2" -le 255 ]] && GRN=$(($2*65535/255)) || GRN=0 ;
        [[ "$3" -gt 0 && "$3" -le 255 ]] && BLU=$(($3*65535/255)) || BLU=0 ;
    fi


    if [[ -z "$OCMD" ]]; then
        OCMD="tell application \"Terminal\" to set background color of window 1 to {$RED, $GRN, $BLU}"
    fi
    # tell user what's going on via stderr
    >&2 echo "#  $OCMD"
    osascript -e "${OCMD}"
}