Make the recurring notifications optional. Sleep exactly as many seconds as needed until the next work needs to be done.

sunset-alarm

@@ -1,21 +1,20 @@
 #!/bin/sh
 
 # sunset-alarm -- Alert before or after sunset.
-# Displays a persistent alert when current time is within
-# (sunset minus specified minutes) of midnight.
+# Displays an alert when current time is within (sunset - specified minutes).
 
 ###############################################################################
 # Defaults
 ###############################################################################
-declare LATLONG="" SUNSET_TIME="" MINUTES="" LAST_DATE=""
-typeset -i SUNSET_EPOCH=0
+declare LATLONG="" SUNSET_TIME="" MINUTES="" LAST_DATE="" PERSIST="" NOTIFIED=""
+typeset -i SUNSET_EPOCH=0 CURRENT_TIME=0
 
 ###############################################################################
 # Usage
 ###############################################################################
 usage() {
     cat <<EOF
-Usage: sunset-alarm (-l LAT:LONG | -t HH24:MI) (-m MINUTES) [-h]
+Usage: sunset-alarm (-l LAT:LONG | -t HH24:MI) (-m MINUTES) [-p] [-h]
 
 Display a notification when a certain time related to sunset has been reached.
 
@@ -25,6 +24,8 @@ Parameters:
     -t) Takes a hard-coded 24-hour formatted time for guessing when sunset is.
     -m) Takes the number of minutes that the alert should appear before sunset.
           Using a negative time is allowed if you prefer having the alert after.
+    -p) Persist the notification, showing back up every 5 minutes to midnight.
+    -h) Display this usage.
 
 Example: Show the alert 90 minutes before sunset in Colorado City AZ.
     sunset-alarm -l 37:-113 -m 90
@@ -46,6 +47,7 @@ while [ $# -gt 0 ]; do
         -l) LATLONG="$2"; shift 2 ;;
         -t) SUNSET_TIME="$2"; shift 2 ;;
         -m) MINUTES="$2"; shift 2 ;;
+        -p) PERSIST="true"; shift 1 ;;
         -h) usage ;;
         --) shift; break ;;
         *) echo "ERROR: unknown argument '$1'" >&2; usage ;;
@@ -141,13 +143,13 @@ show_alert() {
     TITLE="Sunset Alarm ($ALERT)"
     MESSAGE="It's ${MINUTES} minute${PLURAL} to $SUNSET."
 
-    persistent="-t 0 --wait"
+    keep_alive="-t 0 --wait"
     icon="-i weather-clear -u critical"
 
     if command -v fyi >/dev/null 2>&1; then
-        fyi $icon $persistent "$TITLE" "$MESSAGE"
+        fyi $icon $keep_alive "$TITLE" "$MESSAGE"
     elif command -v notify-send >/dev/null 2>&1; then
-        notify-send $icon $persistent "$TITLE" "$MESSAGE"
+        notify-send $icon $keep_alive "$TITLE" "$MESSAGE"
     elif command -v wall >/dev/null 2>&1; then
         echo "${TITLE}: ${MESSAGE}" | wall
     else
@@ -157,6 +159,18 @@ show_alert() {
     fi
 }
 
+###############################################################################
+# Sleep until a certain amount of time
+###############################################################################
+rest() {
+    if [[ "$CURRENT_TIME" -ge 0 ]]; then
+        TARGET="$1"
+        sleep_seconds=$(( TARGET - CURRENT_TIME ))
+        echo "Sleeping ${sleep_seconds}s until $(date -d @$TARGET +%H:%M:%S)."
+        sleep "$sleep_seconds"
+    fi
+}
+
 ###############################################################################
 # Main loop
 ###############################################################################
@@ -208,19 +222,31 @@ while true; do
 
     # Alert while current time is within the window (from window start until midnight).
     if [[ "$SUNSET_EPOCH" -ge 0 \
+        && ( -z "$NOTIFIED" || -n "$PERSIST" ) \
         && "$CURRENT_TIME" -ge "$ALERT_WINDOW_START" \
         && "$CURRENT_TIME" -lt "$MIDNIGHT" ]]
     then
         echo "Alert time has been reached, show message."
         show_alert
+        NOTIFIED="true"
+
         echo "Alert has been dismissed, sleeping for 5 minutes."
         sleep 290
         echo "Waking back up from notification dismissal."
+    elif [[ "$SUNSET_EPOCH" == 0 ]]; then
+        echo "ERROR: Sunset time has not been calculated yet, cannot alert." >&2
+    elif [[ -n "$NOTIFIED" && -z "$PERSIST" ]]; then
+        echo "Already notified for today ($TODAY)."
+        rest $MIDNIGHT
+    else
+        echo "Not time to notify yet."
+        rest $ALERT_WINDOW_START
     fi
 
-    # Reset when we've passed midnight so we fetch new time tomorrow.
+    # Reset when we've passed midnight so we fetch the new time for the day.
     if [[ "$CURRENT_TIME" -ge "$MIDNIGHT" ]]; then
         LAST_DATE=""
+        NOTIFIED=""
     fi
 
     sleep 10