Revert "Taken on board suggestions of Mathieu Lirzin as per e-mails to the bug-mcron@gnu.org mailing list around September 2015."

This reverts commit c0a6eb14c257a47e9573631e5ac09e6528fba377.

1 files changed, 362 insertions, 311 deletions

diff --git a/scm/mcron/main.scm b/scm/mcron/main.scm
index dc839cc..36adef9 100644
--- a/scm/mcron/main.scm
+++ b/scm/mcron/main.scm
@@ -1,4 +1,4 @@
-;;   Copyright (C) 2003, 2012, 2015 Dale Mellor
+;;   Copyright (C) 2003, 2012 Dale Mellor
 ;; 
 ;;   This file is part of GNU mcron.
 ;;
@@ -16,24 +16,34 @@
 ;;   with GNU mcron.  If not, see <http://www.gnu.org/licenses/>.
 
 
-(define-module (mcron main)
-  #:use-module (ice-9 getopt-long)
-  #:use-module (ice-9 rdelim)
-  #:use-module (ice-9 regex)
-  #:use-module (mcron config)
-  #:use-module (mcron mcron-core)
-  #:use-module (mcron job-specifier)
-  #:use-module (mcron vixie-specification)
-  #:use-module (srfi srfi-2)
-  #:use-module (srfi srfi-26)
-  #:export (delete-run-file
-            main))
+
+;; This is the 'main' routine for the whole system; the top of this file is the
+;; global entry point (after the minimal C wrapper, mcron.c.template); to all
+;; intents and purposes the program is pure Guile and starts here.
+;;
+;; This file is built into mcron.c.template by the makefile, which stringifies
+;; the whole lot, and escapes quotation marks and escape characters
+;; accordingly. Bear this in mind when considering literal multi-line strings.
+;;
+;; (l0ad "crontab.scm") (sic) is inlined by the makefile. All other
+;; functionality comes through modules in .../share/guile/site/mcron/*.scm.
+
+
+
+;; Pull in some constants set by the builder (via autoconf) at configuration
+;; time. Turn debugging on if indicated.
+
+(use-modules (mcron config))
+(if config-debug (begin (debug-enable 'debug)
+                        (debug-enable 'backtrace)))
 
 
 
-;; Extract the actual command name from \a command.  This returns the last
-;; part of \a command without any non-alphabetic characters.  For example
-;; "in.cron" and "./mcron" will return respectively "cron" and "mcron".
+;; To determine the name of the program, scan the first item of the command line
+;; backwards for the first non-alphabetic character. This allows names like
+;; in.cron to be accepted as an invocation of the cron command.
+
+(use-modules (ice-9 regex) (ice-9 rdelim))
 
 (define command-name (match:substring (regexp-exec (make-regexp "[[:alpha:]]*$")
                                                    (car (command-line)))))
@@ -41,49 +51,49 @@
 
 
 ;; Code contributed by Sergey Poznyakoff.  Print an error message (made up from
-;; the parts of \a rest), and if the \a exit-code error is fatal (present and
-;; non-zero) then exit to the system with \a exit-code.
+;; the parts of rest), and if the error is fatal (present and non-zero) then
+;; exit to the system with this code.
 
 (define (mcron-error exit-code . rest)
   (with-output-to-port (current-error-port)
     (lambda ()
-      (for-each display
-                (cons* command-name ": " rest))
+      (for-each display (append (list command-name ": ") rest))
       (newline)))
-  (when (and exit-code
-             (not (eq? exit-code 0)))
-    (primitive-exit exit-code)))
+  (if (and exit-code (not (eq? exit-code 0)))
+      (primitive-exit exit-code)))
 
 
 
-;; Code contributed by Sergey Poznyakoff and improved upon by Mathieu Lirzin
-;; with newer guile features.  Execute the expressions.  If an 'mcron-error
+;; Code contributed by Sergey Poznyakoff.  Execute body. If an 'mcron-error
 ;; exception occurs, print its diagnostics and exit with its error code.
 
-(define-syntax-rule (catch-mcron-error exp ...)
-  (catch 'mcron-error
-    (lambda () exp ...)
-    (lambda (key exit-code . msg)
-      (apply mcron-error exit-code msg))))
+(defmacro catch-mcron-error (. body)
+  `(catch 'mcron-error
+          (lambda ()
+            ,@body)
+          (lambda (key exit-code . msg)
+            (apply mcron-error exit-code msg))))
 
 
 
-;; One of the symbols \c mcron, \c crond or \c crontab according to the means
-;; of our invocation.
+;; We will be doing a lot of testing of the command name, so it makes sense to
+;; perform the string comparisons once and for all here.
 
-(define command-type
-  (let ((command=? (cute string=? command-name <>)))
-    (cond ((command=? "mcron") 'mcron)
-          ((or (command=? "cron") (command=? "crond")) 'cron)
-          ((command=? "crontab") 'crontab)
-          (else (mcron-error 12 "The command name is invalid.")))))
+(define command-type (cond ((string=? command-name "mcron") 'mcron)
+                           ((or (string=? command-name "cron")
+                                (string=? command-name "crond")) 'cron)
+                           ((string=? command-name "crontab") 'crontab)
+                           (else
+                            (mcron-error 12 "The command name is invalid."))))
 
 
 
-;; There are a different set of options for the crontab personality compared
-;; to all the others, with the --help and --version options common to all the
+;; There are a different set of options for the crontab personality compared to
+;; all the others, with the --help and --version options common to all the
 ;; personalities.
 
+(use-modules (ice-9 getopt-long))
+
 (define options
   (catch
    'misc-error
@@ -110,96 +120,129 @@
                    '((version  (single-char #\v) (value #f))
                      (help     (single-char #\h) (value #f))))))
    (lambda (key func fmt args . rest)
-     (mcron-error 1 (apply format (cons* #f fmt args))))))
-
-
+     (mcron-error 1 (apply format (append (list #f fmt) args))))))
+
+;; If the user asked for the version of this program, give it to him and get
+;; out.
+
+(if (option-ref options 'version #f)
+    (begin
+      (display (string-append "\n
+" command-name "  (" config-package-string ")\n
+Written by Dale Mellor\n
+\n
+Copyright (C) 2003, 2006, 2014  Dale Mellor\n
+This is free software; see the source for copying conditions.  There is NO\n
+warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.\n
+"))
+      (quit)))
+
+
+
+;; Likewise if the user requested the help text.
+
+(if (option-ref options 'help #f)
+    (begin
+      (display (string-append "
+Usage: " (car (command-line))
+(case command-type
+
+  ((mcron)
+" [OPTIONS] [FILES]\n
+Run an mcron process according to the specifications in the FILES (`-' for\n
+standard input), or use all the files in ~/.config/cron (or the \n
+deprecated ~/.cron) with .guile or .vixie extensions.\n
+\n
+  -v, --version             Display version\n
+  -h, --help                Display this help message\n
+  -sN, --schedule[=]N       Display the next N jobs that will be run by mcron\n
+  -d, --daemon              Immediately detach the program from the terminal\n
+                              and run as a daemon process\n
+  -i, --stdin=(guile|vixie) Format of data passed as standard input or\n
+                              file arguments (default guile)")
 
-;; Display version information for \a command and quit.
+  ((cron)
+" [OPTIONS]\n
+Unless an option is specified, run a cron daemon as a detached process, \n
+reading all the information in the users' crontabs and in /etc/crontab.\n
+\n
+  -v, --version             Display version\n
+  -h, --help                Display this help message\n
+  -sN, --schedule[=]N       Display the next N jobs that will be run by cron\n
+  -n, --noetc               Do not check /etc/crontab for updates (HIGHLY\n
+                              RECOMMENDED).")
+  
+  ((crontab)
+           (string-append " [-u user] file\n"
+           "       " (car (command-line)) " [-u user] { -e | -l | -r }\n"
+           "               (default operation is replace, per 1003.2)\n"
+           "       -e      (edit user's crontab)\n"
+           "       -l      (list user's crontab)\n"
+           "       -r      (delete user's crontab)\n"))
 
-(define* (show-version #:optional (command command-name))
-  (let* ((name       config-package-name)
-         (short-name (cadr (string-split name #\space)))
-         (version    config-package-version))
-    (simple-format #t "~a (~a) ~a
-Copyright (C) 2015 Free Software Foundation, Inc.
+  (else "rubbish"))
 
-License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
-This is free software: you are free to change and redistribute it.
-There is NO WARRANTY, to the extent permitted by law.\n"
-		   command name version)
-    (quit)))
+"\n\n
+Report bugs to " config-package-bugreport ".\n
+"))
+      (quit)))
 
 
 
-;; Display where to get help and send bug reports.
+;; This is called from the C front-end whenever a terminal signal is
+;; received. We 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.
 
-(define (show-package-information)
-  (simple-format #t "\nReport bugs to: ~a.
-~a home page: <~a>
-General help using GNU software: <http://www.gnu.org/gethelp/>\n"
-		 config-package-bugreport
-		 config-package-name
-		 config-package-url))
+(define (delete-run-file)
+  (catch #t (lambda () (delete-file config-pid-file)
+                       (delete-file config-socket-file))
+            noop)
+  (quit))
 
 
 
-;; Display usage information and quit.
+;; Setup the cron process, if appropriate. If there is already a
+;; /var/run/cron.pid file, then we must assume a cron daemon is already running
+;; and refuse to start another one.
+;;
+;; Otherwise, clear the MAILTO environment variable so that output from cron
+;; jobs is sent to the various users (this may still be overridden in the
+;; configuration files), and call the function in the C wrapper to set up
+;; terminal signal responses to vector to the procedure above. The PID file will
+;; be filled in properly later when we have forked our daemon process (but not
+;; done if we are only viewing the schedules).
 
-(define (show-help)
-  (simple-format #t "Usage: ~a" command-name)
-  (display
-   (case command-type
-     ((mcron)
-      " [OPTIONS] [FILES]
-Run an mcron process according to the specifications in the FILES (`-' for
-standard input), or use all the files in ~/.config/cron (or the
-deprecated ~/.cron) with .guile or .vixie extensions.
+(if (eq? command-type 'cron)
+    (begin
+      (if (not (eqv? (getuid) 0))
+          (mcron-error 16
+                       "This program must be run by the root user (and should "
+                       "have been installed as such)."))
+      (if (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
+		       ".)"))
+      (if (not (option-ref options 'schedule #f))
+          (with-output-to-file config-pid-file noop))
+      (setenv "MAILTO" #f)
+      (c-set-cron-signals)))
 
-  -v, --version             Display version
-  -h, --help                Display this help message
-  -sN, --schedule[=]N       Display the next N jobs that will be run by mcron
-  -d, --daemon              Immediately detach the program from the terminal
-                              and run as a daemon process
-  -i, --stdin=(guile|vixie) Format of data passed as standard input or
-                              file arguments (default guile)")
-     ((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).")
-     ((crontab)
-      " [-u user] file
-       crontab [-u user] { -e | -l | -r }
-               (default operation is replace, per 1003.2)
-       -e      (edit user's crontab)
-       -l      (list user's crontab)
-       -r      (delete user's crontab)")
-     (else "\nrubbish")))
-  (newline)
-  (show-package-information)
-  (quit))
 
 
+;; Define the functions available to the configuration files. While we're here,
+;; we'll get the core loaded as well.
 
-;; 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.
+(use-modules (mcron core)
+             (mcron job-specifier)
+             (mcron vixie-specification))
 
-(define (delete-run-file)
-  (catch #t (lambda () (delete-file config-pid-file)
-                       (delete-file config-socket-file))
-            noop)
-  (quit))
 
 
-
-;; Return standard input as a string.
+;; Procedure to slurp the standard input into a string.
 
 (define (stdin->string)
   (with-output-to-string (lambda () (do ((in (read-char) (read-char)))
@@ -208,83 +251,183 @@ reading all the information in the users' crontabs and in /etc/crontab.
 
 
 
-;; Return a thunk which process each file in \a directory with \a proc.  The
-;; \a directory must be a directory name.  The \a proc argument must be a
-;; procedure that takes one file name argument.
+;; Now we have the procedures in place for dealing with the contents of
+;; configuration files, the crontab personality is able to validate such
+;; files. If the user requested the crontab personality, we load and run the
+;; code here and then get out.
+
+(if (eq? command-type 'crontab)
+    (begin
+      (load "crontab.scm")
+      (quit)))
+
+
 
-(define (proc-in-directory directory proc)
-  (let ((dir (opendir directory)))
-    (do ((file-name (readdir dir) (readdir dir)))
-        ((eof-object? file-name) (closedir dir))
-      (proc file-name))))
+;; Code contributed by Sergey Poznyakoff.  Determine if the given file is a
+;; regular file or not.
 
+(define (regular-file? file)
+  (catch 'system-error
+	 (lambda ()
+	   (eq? (stat:type (stat file)) 'regular))
+	 (lambda (key call fmt args . rest)
+	   (mcron-error 0 (apply format (append (list #f fmt) args)))
+	   #f)))
 
 
-;; Process \a file-name according its extension.  When \a guile-syntax? is \c
-;; TRUE, force guile syntax usage.  If \a file-name format is not recognized,
-;; it is silently ignored (this deals properly with most editors' backup
-;; files, for instance).
 
-(define process-user-file
-  (let ((guile-regexp (make-regexp "\\.gui(le)?$"))
-        (vixie-regexp (make-regexp "\\.vix(ie)?$")))
-    (lambda* (file-path #:optional assume-guile)
-      (cond ((string=? "-" file-path)
-             (if (string=? (option-ref options 'stdin "guile") "vixie")
-                 (read-vixie-port (current-input-port))
-                 (eval-string (stdin->string))))
-            ((regexp-exec vixie-regexp file-path)
-             (read-vixie-file file-path))
-            ((or assume-guile
-                 (regexp-exec guile-regexp file-path))
-             (load file-path))))))
+;; Procedure which processes any configuration file according to the
+;; extension. If a file is not recognized, it is silently ignored (this deals
+;; properly with most editors' backup files, for instance).
 
+(define guile-file-regexp (make-regexp "\\.gui(le)?$"))
+(define vixie-file-regexp (make-regexp "\\.vix(ie)?$"))
 
+(define (process-user-file file-path . assume-guile)
+  (cond ((string=? file-path "-")
+               (if (string=? (option-ref options 'stdin "guile") "vixie")
+                   (read-vixie-port (current-input-port))
+                   (eval-string (stdin->string))))
+        ((or (not (null? assume-guile))
+             (regexp-exec guile-file-regexp file-path))
+         (load file-path))
+        ((regexp-exec vixie-file-regexp file-path)
+         (read-vixie-file file-path))))
 
-;; Process files in $XDG_CONFIG_HOME/cron and/or ~/.cron directories (if
-;; $XDG_CONFIG_HOME is not defined uses ~/.config/cron instead).
+
+
+;; Procedure to run through all the files in a user's ~/.cron and/or
+;; $XDG_CONFIG_HOME/cron or ~/.config/cron directories (only happens under the
+;; mcron personality).
 
 (define (process-files-in-user-directory)
   (let ((errors 0)
         (home-directory (passwd:dir (getpw (getuid)))))
-    (map (lambda (dir)
-           (catch #t
-                  (lambda ()
-                    (proc-in-directory
-                     dir
-                     (lambda (file-name)
-                       (process-user-file (string-append dir "/" file-name)))))
-                  (lambda (key . args)
-                    (set! errors (1+ errors)))))
-         (list (string-append home-directory "/.cron")
-               (string-append (or (getenv "XDG_CONFIG_HOME")
-                                  (string-append home-directory "/.config"))
-                              "/cron")))
-    (when (eq? 2 errors)
-      (mcron-error 13
-        "Cannot read files in your ~/.config/cron (or ~/.cron) 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.
+    (map (lambda (config-directory)
+          (catch #t
+                 (lambda ()
+                   (let ((directory (opendir config-directory)))
+                     (do ((file-name (readdir directory) (readdir directory)))
+                         ((eof-object? file-name) (closedir directory))
+                       (process-user-file (string-append config-directory
+                                                         "/"
+                                                         file-name)))))
+                 (lambda (key . args)
+                   (set! errors (1+ errors)))))
+          (list (string-append home-directory "/.cron")
+                (string-append (or (getenv "XDG_CONFIG_HOME")
+                                   (string-append home-directory "/.config"))
+                               "/cron")))
+    (if (eq? 2 errors)
+        (mcron-error 13
+                     "Cannot read files in your ~/.config/cron (or ~/.cron) "
+                     "directory."))))
+
+
+
+;; Procedure to check that a user name is in the passwd database (it may happen
+;; that a user is removed after creating a crontab). If the user name is valid,
+;; the full passwd entry for that user is returned to the caller.
+
+(define (valid-user user-name)
+  (setpwent)
+  (do ((entry (getpw) (getpw)))
+      ((or (not entry)
+           (string=? (passwd:name entry) user-name))
+       (endpwent)
+       entry)))
+
+
+
+;; Procedure to process all the files in the crontab directory, making sure that
+;; each file is for a legitimate user and setting the configuration-user to that
+;; user. In this way, when the job procedure is run on behalf of the
+;; configuration files, the jobs are registered with the system with the
+;; appropriate user. Note that only the root user should be able to perform this
+;; operation, but we leave it to the permissions on the /var/cron/tabs directory
+;; to enforce this.
+
+(use-modules (srfi srfi-2))  ;; For and-let*.
 
 (define (process-files-in-system-directory)
   (catch #t
-    (lambda ()
-      (proc-in-directory
-         config-spool-dir
-         (lambda (user-name)
-           (and-let* ((user (false-if-exception (getpwnam user-name))))
-                     (set-configuration-user user)
-                     (catch-mcron-error
-                       (read-vixie-file
-                          (string-append config-spool-dir "/" user-name)))))))
-    (lambda (key . args)
-      (mcron-error 4
-         "You do not have permission to access the system crontabs."))))
+         (lambda ()
+           (let ((directory (opendir config-spool-dir)))
+             (do ((file-name (readdir directory) (readdir directory)))
+                 ((eof-object? file-name))
+               (and-let* ((user (valid-user file-name)))
+                         (set-configuration-user user)         ;; / ?? !!!!
+                         (catch-mcron-error
+                          (read-vixie-file (string-append config-spool-dir
+                                                          "/"
+                                                          file-name)))))))
+         (lambda (key . args)
+           (mcron-error
+            4
+            "You do not have permission to access the system crontabs."))))
+
+
+
+;; 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.
+
+(case command-type
+  ((mcron) (if (null? (option-ref options '() '()))
+                (process-files-in-user-directory)
+                (for-each (lambda (file-path)
+                            (process-user-file file-path #t))
+                          (option-ref options '() '()))))
+  
+  ((cron) (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)
+   (if (not (option-ref options 'noetc #f))
+       (begin
+         (display
+"WARNING: cron will check for updates to /etc/crontab EVERY MINUTE. If you do\n
+not use this file, or you are prepared to manually restart cron whenever you\n
+make a change, then it is HIGHLY RECOMMENDED that you use the --noetc\n
+option.\n")
+         (set-configuration-user "root")
+         (job '(- (next-minute-from (next-minute)) 6)
+              check-system-crontab
+              "/etc/crontab update checker.")))))
+
+
+
+;; If the user has requested a schedule of jobs that will run, we provide the
+;; information here and then get out.
+;;
+;; Start by determining the number of time points in the future that output is
+;; required for. This may be provided on the command line as a parameter to the
+;; --schedule option, or else we assume a default of 8. Finally, ensure that the
+;; count is some positive integer.
+
+(and-let* ((count (option-ref options 'schedule #f)))
+          (set! count (string->number count))
+          (display (get-schedule (if (<= count 0) 1 count)))
+          (quit))
+    
+
+
+;; If we are supposed to run as a daemon process (either a --daemon option has
+;; been explicitly used, or we are running as cron or crond), detach from the
+;; terminal now. If we are running as cron, we can now write the PID file.
+
+(if (option-ref options 'daemon (eq? command-type 'cron))
+    (begin
+      (if (not (eqv? (primitive-fork) 0))
+          (quit))
+      (setsid)
+      (if (eq? command-type 'cron)
+          (with-output-to-file config-pid-file
+            (lambda () (display (getpid)) (newline))))))
 
 
 
@@ -293,30 +436,32 @@ reading all the information in the users' crontabs and in /etc/crontab.
 ;; inform the main wait-run-wait execution loop to listen for incoming messages
 ;; on this socket.
 
-(define (cron-file-descriptors)
-  (if (eq? command-type 'cron)
-      (catch #t
-             (lambda ()
-               (let ((socket (socket AF_UNIX SOCK_STREAM 0)))
-                 (bind socket AF_UNIX config-socket-file)
-                 (listen socket 5)
-                 (list socket)))
-             (lambda (key . args)
-               (delete-file config-pid-file)
-               (mcron-error 1 
-                 "Cannot bind to UNIX socket " config-socket-file)))
-      '()))
+(define fd-list '())
 
+(if (eq? command-type 'cron)
+    (catch #t
+           (lambda ()
+             (let ((socket (socket AF_UNIX SOCK_STREAM 0)))
+               (bind socket AF_UNIX config-socket-file)
+               (listen socket 5)
+               (set! fd-list (list socket))))
+           (lambda (key . args)
+             (delete-file config-pid-file)
+             (mcron-error 1
+                          "Cannot bind to UNIX socket "
+                          config-socket-file))))
+		     
 
 
-;; Read a user name from the socket, dealing with the /etc/crontab special
+
+;; This function is called whenever a message comes in on the above socket. We
+;; read a user name from the socket, dealing with the "/etc/crontab" special
 ;; case, remove all the user's jobs from the job list, and then re-read the
-;; user's updated file.  In the special case drop all the system jobs and
-;; re-read the /etc/crontab file.  This function should be called whenever a
-;; message comes in on the above socket.
+;; user's updated file. In the special case we drop all the system jobs and
+;; re-read the /etc/crontab file.
 
-(define (process-update-request fd-list)
-  (let* ((socket    (car (accept (car fd-list))))
+(define (process-update-request)
+  (let* ((socket (car (accept (car fd-list))))
          (user-name (read-line socket)))
     (close socket)
     (set-configuration-time (current-time))
@@ -330,123 +475,29 @@ reading all the information in the users' crontabs and in /etc/crontab.
          (let ((user (getpw user-name)))
            (remove-user-jobs user)
            (set-configuration-user user)
-           (read-vixie-file 
-                         (string-append config-spool-dir "/" user-name)))))))
+           (read-vixie-file (string-append config-spool-dir "/" user-name)))))))
 
 
-;; Entry point.
-;;
-;; This is the 'main' routine for the whole system; this module is the global
-;; entry point (after the minimal C wrapper); to all intents and purposes the
-;; program is pure Guile and starts here.
-
-(define (main . args)
-  ;; Added by Sergey Poznyakoff.  This no-op will collect zombie child processes
-  ;; as soon as they die.  This is a big improvement as previously they stayed
-  ;; around the system until the next time mcron wakes to fire a new job off.
-  (when config-debug
-        (debug-enable 'backtrace))
-  (when (option-ref options 'version #f)
-        (show-version))
-  (when (option-ref options 'help #f)
-        (show-help))
-  
-  ;; Setup the cron process, if appropriate. If there is already a
-  ;; /var/run/cron.pid file, then we must assume a cron daemon is already
-  ;; running and refuse to start another one.
-  ;;
-  ;; Otherwise, clear the MAILTO environment variable so that output from cron
-  ;; jobs is sent to the various users (this may still be overridden in the
-  ;; configuration files), and call the function in the C wrapper to set up
-  ;; terminal signal responses to vector to the procedure above. The PID file
-  ;; will be filled in properly later when we have forked our daemon process
-  ;; (but not done if we are only viewing the schedules).
-  (when (eq? command-type 'cron)
-    (unless (eqv? (getuid) 0)
-      (mcron-error 16
-        "This program must be run by the root user (and should have been "
-        "installed as such)."))
-    (when (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 ".)"))
-    (unless (option-ref options 'schedule #f)
-      (with-output-to-file config-pid-file noop))
-    (setenv "MAILTO" #f)
-    ;; Mathieu Lirzin: 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))
-
-  ;; Now we have the procedures in place for dealing with the contents of
-  ;; configuration files, the crontab personality is able to validate such
-  ;; files. If the user requested the crontab personality, we load and run the
-  ;; code here and then get out.
-  (when (eq? command-type 'crontab)
-    (load "crontab.scm")
-    (quit))
-
-  ;; 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.
-  (case command-type
-    ((mcron)
-     (if (null? (option-ref options '() '()))
-         (process-files-in-user-directory)
-         (for-each (lambda (file-path) (process-user-file file-path 
-                                                          'guile-syntax))
-                   (option-ref options '() '()))))
-    ((cron)
-     (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 (option-ref options 'noetc #f)
-       (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."))))
-
-  ;; If the user has requested a schedule of jobs that will run, we provide
-  ;; the information here and then get out.  Start by determining the number
-  ;; of time points in the future that output is required for. This may be
-  ;; provided on the command line as a parameter to the --schedule option, or
-  ;; else we assume a default of 8. Finally, ensure that the count is some
-  ;; positive integer.
-  (and-let* ((count (option-ref options 'schedule #f)))
-            (set! count (string->number count))
-            (display (get-schedule (max 1 count)))
-            (quit))
-
-  ;; If we are supposed to run as a daemon process (either a --daemon option
-  ;; has been explicitly used, or we are running as cron or crond), detach
-  ;; from the terminal now. If we are running as cron, we can now write the
-  ;; PID file.
-  (when (option-ref options 'daemon (eq? command-type 'cron))
-    (unless (eqv? (primitive-fork) 0)
-            (quit))
-    (setsid)
-    (when (eq? command-type 'cron)
-          (with-output-to-file config-pid-file
-            (lambda () (display (getpid)) (newline)))))
-  
-  ;; Now the main loop.  Forever execute the run-job-loop procedure in the
-  ;; mcron core, 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.  Sergey Poznyakoff: we can also drop out of run-job-loop
-  ;; because of a SIGCHLD, so must test fd-list.
-  (catch-mcron-error
-   (let ((fd-list (cron-file-descriptors)))
-     (while #t
-       (run-job-loop fd-list)
-       (unless (null? fd-list)
-         (process-update-request fd-list))))))
+
+;; Added by Sergey Poznyakoff.  This no-op will collect zombie child processes
+;; as soon as they die.  This is a big improvement as previously they stayed
+;; around the system until the next time mcron wakes to fire a new job off.
+
+;; Unfortunately it seems to interact badly with the select system call,
+;; wreaking havoc...
+
+;; (sigaction SIGCHLD (lambda (sig) noop) SA_RESTART)
+
+
+
+;; Now the main loop. Forever execute the run-job-loop procedure in the mcron
+;; core, 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.
+;; Sergey Poznyakoff: we can also drop out of run-job-loop because of a SIGCHLD,
+;; so must test fd-list.
+
+(catch-mcron-error
+ (while #t
+        (run-job-loop fd-list)
+        (if (not (null? fd-list))
+            (process-update-request))))