Merge branch 'devel'

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diff --git a/src/mcron/scripts/cron.scm b/src/mcron/scripts/cron.scm
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+;;;; cron -- daemon for running jobs at scheduled times
+;;; Copyright © 2003, 2012 Dale Mellor <dale_mellor@users.sourceforge.net>
+;;; Copyright © 2015, 2016 Mathieu Lirzin <mthl@gnu.org>
+;;;
+;;; This file is part of GNU Mcron.
+;;;
+;;; GNU Mcron is free software: you can redistribute it and/or modify
+;;; it under the terms of the GNU General Public License as published by
+;;; the Free Software Foundation, either version 3 of the License, or
+;;; (at your option) any later version.
+;;;
+;;; GNU Mcron is distributed in the hope that it will be useful,
+;;; but WITHOUT ANY WARRANTY; without even the implied warranty of
+;;; MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+;;; GNU General Public License for more details.
+;;;
+;;; You should have received a copy of the GNU General Public License
+;;; along with GNU Mcron.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (mcron scripts cron)
+  #:use-module (mcron base)
+  #:use-module (mcron config)
+  #:use-module (mcron job-specifier)
+  #:use-module (mcron utils)
+  #:use-module (mcron vixie-specification)
+  #:use-module (srfi srfi-2)
+  #:export (main))
+
+(define (show-help)
+  (display "Usage: cron [OPTIONS]
+Unless an option is specified, run a cron daemon as a detached process,
+reading all the information in the users' crontabs and in /etc/crontab.
+
+  -v, --version             Display version
+  -h, --help                Display this help message
+  -sN, --schedule[=]N       Display the next N jobs that will be run by cron
+  -n, --noetc               Do not check /etc/crontab for updates (HIGHLY
+                              RECOMMENDED).")
+  (newline)
+  (show-package-information))
+
+(define %options
+  `((schedule (single-char #\s) (value #t)
+              (predicate ,(λ (str) (string->number str))))
+    (noetc    (single-char #\n) (value #f))
+    (version  (single-char #\v) (value #f))
+    (help     (single-char #\h) (value #f))))
+
+(define (delete-run-file)
+  "Remove the /var/run/cron.pid file so that crontab and other invocations of
+cron don't get the wrong idea that a daemon is currently running.  This
+procedure is called from the C front-end whenever a terminal signal is
+received."
+  (catch #t
+    (λ ()
+      (delete-file config-pid-file)
+      (delete-file config-socket-file))
+    noop)
+  (quit))
+
+(define (cron-file-descriptors)
+  "Establish a socket to listen for updates from a crontab program, and return
+a list containing the file descriptors correponding to the files read by
+crontab.  This requires that command-type is 'cron."
+  (catch #t
+    (λ ()
+      (let ((sock (socket AF_UNIX SOCK_STREAM 0)))
+        (bind sock AF_UNIX config-socket-file)
+        (listen sock 5)
+        (list sock)))
+    (λ (key . args)
+      (delete-file config-pid-file)
+      (mcron-error 1 "Cannot bind to UNIX socket " config-socket-file))))
+
+(define (process-files-in-system-directory)
+  "Process all the files in the crontab directory.  When the job procedure is
+run on behalf of the configuration files, the jobs are registered on the
+system with the appropriate user.  Only root should be able to perform this
+operation.  The permissions on the /var/cron/tabs directory enforce this."
+
+  (define (user-entry name)
+    ;; Return the user database entry if NAME is valid, otherwise #f.
+    (false-if-exception (getpwnam name)))
+
+  (catch #t
+    (λ ()
+      (for-each-file
+       (λ (user)
+         (and-let* ((entry (user-entry user))) ;crontab without user?
+           (set-configuration-user entry)
+           (catch-mcron-error
+            (read-vixie-file (string-append config-spool-dir "/" user)))))
+       config-spool-dir))
+    (λ (key . args)
+      (mcron-error 4
+        "You do not have permission to access the system crontabs."))))
+
+(define (%process-files schedule? noetc?)
+  ;; XXX: What is this supposed to do?
+  (when schedule?
+    (with-output-to-file config-pid-file noop))
+  ;; Clear MAILTO so that outputs are sent to the various users.
+  (setenv "MAILTO" #f)
+  ;; XXX: At compile time, this yields a "possibly unbound variable" warning,
+  ;; but this is OK since it is bound in the C wrapper.
+  (c-set-cron-signals)
+  ;; Having defined all the necessary procedures for scanning various sets of
+  ;; files, we perform the actual configuration of the program depending on
+  ;; the personality we are running as. If it is mcron, we either scan the
+  ;; files passed on the command line, or else all the ones in the user's
+  ;; .config/cron (or .cron) directory. If we are running under the cron
+  ;; personality, we read the /var/cron/tabs directory and also the
+  ;; /etc/crontab file.
+  (process-files-in-system-directory)
+  (use-system-job-list)
+  (catch-mcron-error
+   (read-vixie-file "/etc/crontab" parse-system-vixie-line))
+  (use-user-job-list)
+  (unless noetc?
+    (display "\
+WARNING: cron will check for updates to /etc/crontab EVERY MINUTE. If you do
+not use this file, or you are prepared to manually restart cron whenever you
+make a change, then it is HIGHLY RECOMMENDED that you use the --noetc
+option.\n")
+    (set-configuration-user "root")
+    (job '(- (next-minute-from (next-minute)) 6)
+         check-system-crontab
+         "/etc/crontab update checker.")))
+
+
+;;;
+;;; Entry point.
+;;;
+
+(define* (main #:optional (args (command-line)))
+  (let ((opts (parse-args args %options)))
+    (when config-debug
+      (debug-enable 'backtrace))
+    (cond
+     ((option-ref opts 'help #f)
+      (show-help)
+      (exit 0))
+     ((option-ref opts 'version #f)
+      (show-version "cron")
+      (exit 0))
+     ((not (zero? (getuid)))
+      (mcron-error 16
+        "This program must be run by the root user (and should"
+        " have been installed as such)."))
+     ((access? config-pid-file F_OK)
+      (mcron-error 1
+        "A cron daemon is already running.\n  (If you are sure"
+        " this is not true, remove the file\n   "
+        config-pid-file ".)"))
+     (else
+      (%process-files (option-ref opts 'schedule #f)
+                      (option-ref opts 'noetc #f))
+      (cond ((option-ref opts 'schedule #f) ;display jobs schedule
+             => (λ (count)
+                  (display (get-schedule (max 1 (string->number count))))
+                  (exit 0)))
+            (else (case (primitive-fork) ;run the daemon
+                    ((0)
+                     (setsid)
+                     ;; we can now write the PID file.
+                     (with-output-to-file config-pid-file
+                       (λ () (display (getpid)) (newline))))
+                    (else (exit 0)))))
+      ;; Forever execute the 'run-job-loop', and when it drops out (can
+      ;; only be because a message has come in on the socket) we
+      ;; process the socket request before restarting the loop again.
+      (catch-mcron-error
+       (let ((fdes-list (cron-file-descriptors)))
+         (while #t
+           (run-job-loop fdes-list)
+           (unless (null? fdes-list)
+             (process-update-request fdes-list)))))))))