kiwi-cron/cron-exec

#!/bin/sh

crontab_append () {
  crontab="$(
    printf '%s\n%s' \
      "${crontab}" "${1}"
  )"
}

print_cron_schedule() {
    cas_min="${1}"
    cas_hour="${2}"
    cas_day="${3}"
    cas_month="${4}"
    cas_weekday="${5}"
    cas_command="${6}"
    
    printf '%-8s%-8s%-8s%-8s%-8s%s\n' \
      "${cas_min}" "${cas_hour}" "${cas_day}" "${cas_month}" "${cas_weekday}" "${cas_command}"
}

crontab='# crontab generated for kiwi-cron'
crontab_append '# generation time: '"$(date)"
crontab_append '#'
crontab_append "$( 
  print_cron_schedule \
    "# min" "hour" "day" "month" "weekday" "command" 
)"

# check *ly dirs in root directory
schedule_dirs="$( 
  find "/kiwi-cron" -type d -name "*ly" -mindepth 1 -maxdepth 1
)"

for schedule_dir in ${schedule_dirs}; do
  # count files in scheduler directory
  schedule_filecount="$( 
    find "${schedule_dir}" -type f -mindepth 1 -maxdepth 1 \
    | wc -l
  )"

  # ignore if empty
  if [ "${schedule_filecount}" -eq "0" ]; then
    continue
  fi

  # infer cron schedule by directory name
  units="${schedule_dir##*/}"

  case "${units}" in
    hourly)
      crontab_append "$( 
        print_cron_schedule \
          "0" "*" "*" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    daily)
      crontab_append "$( 
        print_cron_schedule \
          "0" "2" "*" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    weekly)
      crontab_append "$( 
        print_cron_schedule \
          "0" "3" "*" "*" "6" "run-parts '${schedule_dir}'" 
      )"
      ;;

    monthly)
      crontab_append "$( 
        print_cron_schedule \
          "0" "5" "1" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    yearly|annually)
      crontab_append "$( 
        print_cron_schedule \
          "0" "0" "1" "1" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;
  esac
done

# check dirs in "every" subdirectory
every_schedule_dirs="$( 
  find "/kiwi-cron/every" -type d -mindepth 1 -maxdepth 1
)"

for schedule_dir in ${every_schedule_dirs}; do
  # count files in scheduler directory
  schedule_filecount="$( 
    find "${schedule_dir}" -type f -mindepth 1 -maxdepth 1 \
    | wc -l
  )"

  # ignore if empty
  if [ "${schedule_filecount}" -eq "0" ]; then
    continue
  fi

  # infer cron schedule by directory name
  schedule="${schedule_dir##*/}"
  every="$( echo "${schedule}" | awk -F_ '{print $1}' )"
  units="$( echo "${schedule}" | awk -F_ '{print $2}' )"
  units="${units%s}"

  # generate valid random values
  rand_min=$(( RANDOM % 60 ))
  # rand_hour=$(( RANDOM % 24 ))
  # generating nighttime values seems like a good idea!
  rand_hour=$(( (RANDOM % 7 + 21) % 24 ))
  rand_day=$(( RANDOM % 31 + 1 ))

  case "${units}" in
    minute)
      crontab_append "$( 
        print_cron_schedule \
          "*/${every}" "*" "*" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    hour)
      crontab_append "$( 
        print_cron_schedule \
          "${rand_min}" "*/${every}" "*" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    day)
      crontab_append "$( 
        print_cron_schedule \
          "${rand_min}" "${rand_hour}" "*/${every}" "*" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;

    month)
      crontab_append "$( 
        print_cron_schedule \
          "${rand_min}" "${rand_hour}" "${rand_day}" "*/${every}" "*" "run-parts '${schedule_dir}'" 
      )"
      ;;
  esac
done

# replace crontab
echo "${crontab}" | crontab -
exec crond -fd 8