Fireworks from the Command Line

To kick off the upcoming 4th of July celebrations we present the following bash script for your enjoyment.

If you'd rather not try to figure out what it does, watch the video.

Have a safe and Happy 4th of July!

#!/bin/bash

rows=$(tput lines)
cols=$(tput cols)
colors=(red green blue purple cyan yellow brown)
lock_file=
lock_file_base=/tmp/$(basename $0 .sh)

multiple=0
if [[ "$1" ]]; then
    nsingle=$1
    shift
else
    nsingle=10
fi
if [[ "$1" ]]; then
    nmultiple=$1
    shift
    if [[ $nmultiple -gt 8 ]]; then nmultiple=8; fi
else
    nmultiple=6
fi


function colorstr()
{
    local  row=$1
    local  col=$2
    local  color=$3
    local  v
    case "$color" in
    red)     v=31;;
    green)   v=34;;
    blue)    v=32;;
    purple)  v=35;;
    cyan)    v=36;;
    yellow)  v=33;;
    brown)   v=33;;
    white)   v=37;;
    *)       v=;;
    esac
    shift 3

    if [[ $multiple -ne 0 ]]; then
        touch $lock_file
        while [[ $(ls $lock_file_base.* 2>/dev/null | head -n 1) != $lock_file ]]
        do
            sleep 0.05
        done
    fi
        
    tput cup $row $col
    echo -n -e "\e["$v"m"
    set -f
    echo -n $*
    set +f
    if [[ $multiple -ne 0 ]]; then
        rm -f $lock_file
    fi
}

function center_colorstr()
{
    local  row=$1
    local  color=$2
    shift 2
    local  s="$*"
    local  slen=${#s}
    colorstr $row $(((cols / 2) - (slen / 2))) $color "$s"
}

function fireworks()
{
    local row=$((rows - 1))
    local col=$(((RANDOM % (cols / 2)) + (cols / 4)))
    local height=$((RANDOM % rows - 2))
    local slant
    local h
    local color1=${colors[$((RANDOM % ${#colors[*]}))]}
    local color2=${colors[$((RANDOM % ${#colors[*]}))]}
    local color3=${colors[$((RANDOM % ${#colors[*]}))]}
    while [[ $color1 == $color2  ||  $color1 == $color3  ||  $color2 == $color3 ]]
    do
        color2=${colors[$((RANDOM % ${#colors[*]}))]}
        color3=${colors[$((RANDOM % ${#colors[*]}))]}
    done

    case $((RANDOM % 4)) in
    0) slant=-2;;
    1) slant=-1;;
    2) slant=1;;
    3) slant=2;;
    esac

    if [[ $height -gt 5 ]]; then
        h=$height

        while [[ $h -gt 0 ]]
        do
            colorstr $row $col $color1 '.'
            let row--
            if [[ $((col + slant)) -ge $((cols - 3))  ||  $((col + slant)) -le 2 ]]; then break; fi
            let col+=slant
            let h--
            sleep 0.1
        done

        if [[ $((col + slant)) -lt $((cols - 3))  &&  $((col + slant)) -gt 2 ]]; then

            h=$((height / 5))

            while [[ $h -gt 0 ]]
            do
                colorstr $row $col $color2 '.'
                let row++
                if [[ $((col + slant)) -ge $((cols - 3))  ||  $((col + slant)) -le 2 ]]; then break; fi
                let col+=slant
                let h--
                sleep 0.1
            done
        fi

        colorstr $((row)) $((col - 1)) $color3 '***'
        colorstr $((row - 1)) $((col)) $color3 '*'
        colorstr $((row + 1)) $((col)) $color3 '*'
    fi
}

for i in $(seq 1 $nsingle)
do
    clear
    fireworks
    sleep 1
done

clear

pids=
for i in $(seq 1 $nmultiple)
do
    let multiple++
    lock_file=$lock_file_base.$i
    fireworks &
    pids="$pids $!"
done

trap "kill -9 $pids 2>/dev/null" EXIT

wait $pids
sleep 3

clear
center_colorstr $((rows / 2 - 1)) red "Hope you enjoyed the show!"
center_colorstr $((rows / 2 + 1)) red "Happy 4th of July"
center_colorstr $((rows / 2 + 3)) red "Your Friends at Linux Journal"
echo

sleep 5
clear


# vim: tabstop=4: shiftwidth=4: noexpandtab:
# kate: tab-width 4; indent-width 4; replace-tabs false;
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