Breaks notification

#!/bin/bash

# The script reminds to take breaks. It checks the uptime and the
# current time and depending on their values opens a notification
# window saying either to turn off the computer or to exercise;
# alternatively it just beeps. The script is started as a cron job
# every half an hour, so an appropriate entry should be created. The
# script uses espeak, yad, uptime, date, sox and a GTK icon set; so
# they should be installed on the machine.

function announcement()
{
    espeak -v english "$1" &
    yad --notification --image="$2"
    yad --title="Break!" --text="$3" --image="$4" --borders=8 --width=256 --button='Dismiss!gtk-cancel'
    exit 0
}

hours_of_uptime=$(uptime -p | cut -d ' ' -f 2)
minutes_of_uptime=$(uptime -p | cut -d ' ' -f 4)

if (("$hours_of_uptime" % 3 == 0)) && (("$minutes_of_uptime" < 30)); then
    announcement "Relax!" "emblem-colors-red" "Turn off the computer!" "exit"
fi

current_hour=$(date +%H)
hours_no_leading_zeros=${current_hour#0}
current_minute=$(date +%M)
minutes_no_leading_zeros=${current_minute#0}
total_minutes=$((minutes_no_leading_zeros + hours_no_leading_zeros * 60))

if ((total_minutes % 90 == 0)); then
    announcement "Exercise!" "emblem-colors-yellow" "Exercise!" "applications-sports"
fi

play -n synth 0.05 sine 220 vol -20dB