sleep until a quantized time, implemented in both Bourne shell and Go

quantized-sleep.go

package main

import (
	"flag"
	"fmt"
	"time"
)

func main() {
	multiple := flag.Duration("multiple", 5*time.Minute, "sleep until the next integer multiple of this time")
	sleepchunk := flag.Duration("sleep-chunk", 5*time.Second, "sleep in blocks of up to this much")
	flag.Parse()
	now := time.Now()
	nextmultiple := now.Truncate(*multiple).Add(*multiple)
	fmt.Printf("target time is %v\n", nextmultiple)
	for {
		remaining := time.Until(nextmultiple)
		if remaining < 0 {
			break
		}
		fmt.Printf("time now is %v, time left to sleep is %v\n", time.Now(), remaining)
		if remaining < *sleepchunk {
			time.Sleep(remaining)
		} else {
			time.Sleep(*sleepchunk)
		}
	}
	fmt.Printf("time now is %v\n", time.Now())
}

quantized-sleep.sh

#!/bin/sh

# quantizing amount, in seconds
chunk=300

# maximum sleep time
incr=15

while getopts "c:i:" opt ; do
  case "$opt" in
    c) chunk="$OPTARG" ;;
    i) incr="$OPTARG" ;;
    *) echo "usage: quantized-sleep.sh [-c CHUNKSECONDS] [-i INCREMENTSECONDS]" >&2; exit 1 ;;
  esac
done

# date math
now=$(date +%s)
last=$((now - now % chunk))
next=$((last + chunk))

while true ; do
  now=$(date +%s)
  sleep=$((next-now))
  echo "last=$last, now=$(date +%s), next=$next, remaining=$sleep"
  if [ "$sleep" -ge "$incr" ] ; then
    sleep "$incr"
  else
    sleep "$sleep"
    break
  fi
done
date

sample-output.txt

$ ./quantized-sleep.sh -c 30 -i 15
last=1579786080, now=1579786095, next=1579786110, remaining=15
last=1579786080, now=1579786110, next=1579786110, remaining=0
Fri 24 Jan 2020 00:28:30 AEDT

$ ./quantized-sleep.sh -c 30 -i 5
last=1579786260, now=1579786262, next=1579786290, remaining=28
last=1579786260, now=1579786267, next=1579786290, remaining=23
last=1579786260, now=1579786272, next=1579786290, remaining=18
last=1579786260, now=1579786277, next=1579786290, remaining=13
last=1579786260, now=1579786282, next=1579786290, remaining=8
last=1579786260, now=1579786287, next=1579786290, remaining=3
Fri 24 Jan 2020 00:31:30 AEDT