Develop simple pomodoro posix shell script

pomodoro.sh

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+#!/bin/sh
+
+sl=25 # study session time in minutes
+bl=5 # break time in minutes
+bll=20 # long break time in minutes
+bls=4 # number of study sessions before long break
+ringtone="$HOME/Media/warcraft-soundtrack/2004 World of Warcraft/ringtone.flac"
+
+sessions=0 # number of sessions passed
+# if you kill and restart pomodoro.sh, you can specify the number of sessions passed
+[ $# -gt 0 ] && sessions=$1
+
+printf "\rStudy time! Sessions done: %d\n" "$sessions"
+notify-send -i "media-playback-playing" "Study time!"
+start="$(date +%s)" # start time stamp
+state=0 # 0 - study, 1 - relax, 2 - long break
+tl=$sl # current time limit
+
+while :
+do
+    now="$(date +%s)"
+
+    left=$((tl * 60 - (now - start)))
+
+    printf "\033[K\r%02d:%02d" "$((left / 60))" "$((left % 60))"
+
+    if [ $left -le 0 ]; then
+        printf "\033[1A\033[K"
+        if [ $state -eq 0 ]; then
+            sessions=$((sessions + 1))
+            if [ $((sessions % bls)) -eq 0 ]; then
+                state=2
+                printf "\rLong break time! Sessions done: %d\n" "$sessions"
+                notify-send -i "media-playback-paused" "Long break time!"
+                mpv --no-vid --no-terminal "$ringtone" &
+                tl=$bll
+            else
+                state=1
+                printf "\rBreak time! Sessions done: %d\n" "$sessions"
+                notify-send -i "media-playback-paused" "Break time!"
+                mpv --no-vid --no-terminal "$ringtone" &
+                tl=$bl
+            fi
+        else
+            state=0
+            printf "\rStudy time! Sessions done: %d\n" "$sessions"
+            notify-send -i "media-playback-playing" "Study time!"
+            mpv --no-vid --no-terminal "$ringtone" &
+            tl=$sl
+        fi
+
+        mpvpid=$!
+
+        printf "%s " "Press Enter to start the timer"
+        read ans
+        printf "\033[1A\033[K"
+
+        start="$(date +%s)"
+        kill $mpvpid 2> /dev/null
+    fi
+
+    sleep 1
+done