Set or refresh a timed shutdown of a machine

vm-shutdown.sh

#!/usr/bin/env bash
#
# Usage: vm-shutdown.sh [--check|--cancel|--help]
#
# Schedule a shutdown of the system at a time in the future.
# With --check, do not schedule a shutdown, just print the scheduled time.
# With --cancel, cancel a pending shutdown.
#
# Installation:
#
# - Copy this script somewhere in your $PATH.
# - Ensure the script is run on each login, e.g., from .bash_profile.
#
# The default shutdown period is 4 hours; edit "howlong" below to use a
# different period. Run the script explicitly at any time to refresh the
# timeout.
set -euo pipefail

# Location of the scheduled shutdown record (if there is one).
timefile=/run/systemd/shutdown/scheduled

# How long until shutdown (minutes).
howlong=240

whendown() {
  if [[ ! -f "$timefile" ]] ; then
    echo "no shutdown scheduled"
  else
    date --date=@"$(head -1 "$timefile" | cut -d= -f2 | rev | cut -c7- | rev)"
  fi
}

case "${1:-}" in
  (-check|--check|-when|--when)
      whendown
      exit 0
      ;;
  (-c|-cancel|--cancel)
      sudo shutdown --no-wall -c
      echo "shutdown cancelled" 1>&2
      exit 0
      ;;
  (-h|-help|--help)
      echo "Run without arguments to reset shutdown." 1>&2
      echo "  Use --check to check how long is left until shutdown" 1>&2
      echo "  Use --cancel to disable a pending shutdown" 1>&2
      exit 1
      ;;
  (?*)
      echo "Unknown option ${1}" 1>&2
      exit 2
      ;;
esac

sudo shutdown --no-wall +"$howlong" 2>/dev/null
printf "Shutdown at: %s\n" "$(whendown)" 1>&2