version with cron-exec script

Dockerfile

@@ -2,10 +2,22 @@ FROM alpine:latest
 
 RUN set -ex; \
     \
-    mkdir /etc/periodic/5min; \
+    mkdir -pm 755 /kiwi-cron; \
-    chmod 755 /etc/periodic/5min;
+    cd /kiwi-cron; \
+    mkdir -pm 755 \
+        every/5_minutes \
+        every/15_minutes \
+        hourly \
+        daily \
+        weekly \
+        monthly \
+        yearly \
+    ; \
+    \
+    apk --no-cache add \
+        docker-cli \
+    ;
 
-ENTRYPOINT [ "/usr/sbin/crond" ]
+COPY cron-exec /usr/local/bin/
-CMD [ "-fd", "8" ]
 
-COPY crontab /var/spool/cron/crontabs/root
+CMD [ "cron-exec" ]

README.md

@@ -8,11 +8,18 @@ Simple cron-jobs  for [`kiwi-scp`](https://github.com/ldericher/kiwi-scp)
 
 ## Quick start
 
-kiwi-cron comes with a pre-loaded cron daemon for periodic jobs. Just drop your executables into the relevant directory under `/etc/periodic/` and that's it.
+kiwi-cron comes with a pre-configured cron daemon for periodic jobs. 
+Just drop your scripts into the relevant directory under `/kiwi-cron/` and that's it.
 
-- `/etc/periodic/5min` -- is run every 5 minutes
+- `/kiwi-cron/hourly` – is run every full hour
-- `/etc/periodic/15min` -- is run every 15 minutes
+- `/kiwi-cron/daily` – is run every day at 2 am
-- `/etc/periodic/hourly` -- is run every full hour
+- `/kiwi-cron/weekly` – is run every saturday at 3 am
-- `/etc/periodic/daily` -- is run every day at 2am
+- `/kiwi-cron/monthly` – is run on the first day of every month at 5 am
-- `/etc/periodic/weekly` -- is run every saturday at 3am
+- `/kiwi-cron/yearly` and `/kiwi-cron/annually` – is run on every January 1st at 12 am
-- `/etc/periodic/month` -- is run on the first day of every month at 5am
+
+## `/kiwi-cron/every` directory
+
+You can use directories like `/kiwi-cron/every/5_minutes` to run scripts every 5 minutes. 
+`kiwi-cron` automatically picks up on that format and generates cron schedules for you.
+
+You can define schedules to be run every N minutes, hours, days, or months that way.

cron-exec

@@ -0,0 +1,151 @@
+#!/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

crontab

@@ -1,9 +0,0 @@
-# cron jobs by kiwi-scp
-#
-# min   hour    day     month   weekday command
-*/5     *       *       *       *       run-parts /etc/periodic/5min
-*/15    *       *       *       *       run-parts /etc/periodic/15min
-0       *       *       *       *       run-parts /etc/periodic/hourly
-0       2       *       *       *       run-parts /etc/periodic/daily
-0       3       *       *       6       run-parts /etc/periodic/weekly
-0       5       1       *       *       run-parts /etc/periodic/monthly