dong (feature-request)

[rborder]

Killer app. I'd like to request a "dong mode" where you can ask for a chime based on system time. E.g.

dong 15m

Would trigger the chime every at HH:{00,15,30,45} until the program is killed.

[rlue]

This is an interesting request, but as stated, leads to irregular behavior for inputs that are not factors of 60. E.g., dong 17m would presumably chime at HH:{00,17,34,51}, which results in a shorter (9m) interval at the end of every hour. And what happens for dong 67m?

A good solution to this problem might be to accept cron syntax, but I suspect that would entail a significant rewrite of the timer logic. If you only ever need it for 15-minute intervals, IMO the easiest thing to do would be to define a bash function that calculates how many seconds remain until the next quarter-hour, then invoke timer with a delay for that long, on infinite repeat.

Lucky for you, I already have one that I wrote way back in 2017:

if [ "$(type -t dlt)" = "alias" ]; then
	unalias dlt
fi

function dlt() {
  mins_to_next_qt_hour=$(("15 - $(date +%M) % 15"))

  if [ $mins_to_next_qt_hour -eq 1 ]; then
    mins_to_next_qt_hour=16
  fi

  timer -qd $(("60 * $mins_to_next_qt_hour - $(date +%S)")) -r -1 15 &
  disown
}

Add to your .bashrc. Kill with pkill -nf timer.

[rborder]

This is an interesting request, but as stated, leads to irregular behavior for inputs that are not factors of 60. E.g., dong 17m would presumably chime at HH:{00,17,34,51}, which results in a shorter (9m) interval at the end of every hour. And what happens for dong 67m?

The natural solution would be chime at the union of x*n mod 60 for all natural numbers n. So for any prime other than 2,3, or 5 you will simply chime every minute.