Juggled build infrastructure to make mcron.1 man page properly.

1 files changed, 228 insertions, 0 deletions

diff --git a/scm/mcron/crontab.scm b/scm/mcron/crontab.scm
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+;;   Copyright (C) 2003, 2014 Dale Mellor
+;; 
+;;   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/>.
+
+
+;; Apart from the collecting of options and the handling of --help and --version
+;; (which are done in the main.scm file), this file provides all the
+;; functionality of the crontab personality. It is designed to be loaded and run
+;; once, and then the calling program can exit and the crontab program will have
+;; completed its function.
+
+
+
+;; Procedure to communicate with running cron daemon that a user has modified
+;; his crontab. The user name is written to the /var/cron/socket UNIX socket.
+
+(let ((hit-server
+       (lambda (user-name)
+         (catch #t (lambda ()
+                     (let ((socket (socket AF_UNIX SOCK_STREAM 0)))
+                       (connect socket AF_UNIX config-socket-file)
+                       (display user-name socket)
+                       (close socket)))
+                (lambda (key . args)
+                  (display "Warning: a cron daemon is not running.\n")))))
+
+
+
+;; Procedure to scan a file containing one user name per line (such as
+;; /var/cron/allow and /var/cron/deny), and determine if the given name is in
+;; there. The procedure returns #t, #f, or '() if the file does not exist.
+
+      (in-access-file?
+       (lambda (file name)
+         (catch #t (lambda ()
+                     (with-input-from-file
+                         file
+                       (lambda ()
+                         (let loop ((input (read-line)))
+                           (if (eof-object? input)
+                               #f
+                               (if (string=? input name)
+                                   #t
+                                   (loop (read-line))))))))
+                (lambda (key . args) '()))))
+      
+      
+
+      ;; This program should have been installed SUID root. Here we get the
+      ;; passwd entry for the real user who is running this program.
+
+      (crontab-real-user (passwd:name (getpw (getuid)))))
+
+
+
+  ;; If the real user is not allowed to use crontab due to the /var/cron/allow
+  ;; and/or /var/cron/deny files, bomb out now.
+
+  (if (or (eq? (in-access-file? config-allow-file crontab-real-user) #f)
+          (eq? (in-access-file? config-deny-file crontab-real-user) #t))
+      (mcron-error 6 "Access denied by system operator."))
+  
+
+
+  ;; Check that no more than one of the mutually exclusive options are being
+  ;; used.
+
+  (if (> (+ (if (option-ref options 'edit #f) 1 0)
+            (if (option-ref options 'list #f) 1 0)
+            (if (option-ref options 'remove #f) 1 0))
+         1)
+      (mcron-error 7 "Only one of options -e, -l or -r can be used."))
+
+
+
+  ;; Check that a non-root user is trying to read someone else's files.
+
+  (if (and (not (eqv? (getuid) 0))
+           (option-ref options 'user #f))
+      (mcron-error 8 "Only root can use the -u option."))
+
+
+
+  (let (
+
+  
+        ;; Iff the --user option is given, the crontab-user may be different
+        ;; from the real user.
+
+        (crontab-user (option-ref options 'user crontab-real-user))
+
+
+        ;; So now we know which crontab file we will be manipulating.
+        
+        (crontab-file (string-append config-spool-dir "/" crontab-user))
+
+
+
+        ;; Display the prompt and wait for user to type his choice. Return #t if
+        ;; the answer begins with 'y' or 'Y', return #f if it begins with 'n' or
+        ;; 'N', otherwise ask again.
+
+        (get-yes-no (lambda (prompt . re-prompt)
+                      (if (not (null? re-prompt))
+                          (display "Please answer y or n.\n"))
+                      (display (string-append prompt " "))
+                      (let ((r (read-line)))
+                        (if (not (string-null? r))
+                            (case (string-ref r 0)
+                              ((#\y #\Y) #t)
+                              ((#\n #\N) #f)
+                              (else (get-yes-no prompt #t)))
+                            (get-yes-no prompt #t))))))
+
+
+
+    ;; There are four possible sub-personalities to the crontab personality:
+    ;; list, remove, edit and replace (when the user uses no options but
+    ;; supplies file names on the command line).
+
+    (cond
+
+
+ ;; In the list personality, we simply open the crontab and copy it
+ ;; character-by-character to the standard output. If anything goes wrong, it
+ ;; can only mean that this user does not have a crontab file.
+ 
+ ((option-ref options 'list #f)
+  (catch #t (lambda ()
+              (with-input-from-file crontab-file (lambda ()
+                 (do ((input (read-char) (read-char)))
+                     ((eof-object? input))
+                   (display input)))))
+         (lambda (key . args)
+           (display (string-append "No crontab for "
+                                   crontab-user
+                                   " exists.\n")))))
+
+
+ ;; In the edit personality, we determine the name of a temporary file and an
+ ;; editor command, copy an existing crontab file (if it is there) to the
+ ;; temporary file, making sure the ownership is set so the real user can edit
+ ;; it; once the editor returns we try to read the file to check that it is
+ ;; parseable (but do nothing more with the configuration), and if it is okay
+ ;; (this program is still running!) we move the temporary file to the real
+ ;; crontab, wake the cron daemon up, and remove the temporary file. If the
+ ;; parse fails, we give user a choice of editing the file again or quitting
+ ;; the program and losing all changes made.
+
+ ((option-ref options 'edit #f)
+  (let ((temp-file (string-append config-tmp-dir
+                                  "/crontab."
+                                  (number->string (getpid)))))
+    (catch #t (lambda () (copy-file crontab-file temp-file))
+              (lambda (key . args) (with-output-to-file temp-file noop)))
+    (chown temp-file (getuid) (getgid))
+    (let retry ()
+      (system (string-append
+               (or (getenv "VISUAL") (getenv "EDITOR") "vi")
+               " "
+               temp-file))
+      (catch 'mcron-error
+             (lambda () (read-vixie-file temp-file))
+             (lambda (key exit-code . msg)
+               (apply mcron-error 0 msg)
+               (if (get-yes-no "Edit again?")
+                   (retry)
+                   (begin
+                     (mcron-error 0 "Crontab not changed")
+                     (primitive-exit 0))))))
+    (copy-file temp-file crontab-file)
+    (delete-file temp-file)
+    (hit-server crontab-user)))
+
+
+ ;; In the remove personality we simply make an effort to delete the crontab and
+ ;; wake the daemon. No worries if this fails.
+
+ ((option-ref options 'remove #f)
+  (catch #t (lambda () (delete-file crontab-file)
+                       (hit-server crontab-user))
+            noop))
+
+
+ ;; !!!!  This comment is wrong.
+ 
+ ;; In the case of the replace personality we loop over all the arguments on the
+ ;; command line, and for each one parse the file to make sure it is parseable
+ ;; (but subsequently ignore the configuration), and all being well we copy it
+ ;; to the crontab location; we deal with the standard input in the same way but
+ ;; different. :-)  In either case the server is woken so that it will read the
+ ;; newly installed crontab.
+
+ ((not (null? (option-ref options '() '())))
+  (let ((input-file (car (option-ref options '() '()))))
+    (catch-mcron-error
+     (if (string=? input-file "-")
+         (let ((input-string (stdin->string)))
+           (read-vixie-port (open-input-string input-string))
+           (with-output-to-file crontab-file (lambda ()
+                                               (display input-string))))
+         (begin
+           (read-vixie-file input-file)
+           (copy-file input-file crontab-file))))
+    (hit-server crontab-user)))
+ 
+ 
+ ;; The user is being silly. The message here is identical to the one Vixie cron
+ ;; used to put out, for total compatibility.
+
+ (else
+  (mcron-error 15 "usage error: file name must be specified for replace.")))
+
+
+)) ;; End of file-level let-scopes.