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

1 files changed, 189 insertions, 0 deletions

diff --git a/scm/mcron/redirect.scm b/scm/mcron/redirect.scm
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@@ -0,0 +1,189 @@
+;;   Copyright (C) 2003 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/>.
+
+
+
+;; This module provides the (with-mail-out action . user) procedure. This
+;; procedure runs the action in a child process, allowing the user control over
+;; the input and output (including standard error). The input is governed (only
+;; in the case of a string action) by the placing of percentage signs in the
+;; string; the first delimits the true action from the standard input, and
+;; subsequent ones denote newlines to be placed into the input. The output (if
+;; there actually is any) is controlled by the MAILTO environment variable. If
+;; this is not defined, output is e-mailed to the user passed as argument, if
+;; any, or else the owner of the action; if defined but empty then any output is
+;; sunk to /dev/null; otherwise output is e-mailed to the address held in the
+;; MAILTO variable.
+
+(define-module (mcron redirect)
+  #:export (with-mail-out)
+  #:use-module ((mcron config) :select (config-sendmail))
+  #:use-module (mcron vixie-time))
+
+
+
+;; An action string consists of a sequence of characters forming a command
+;; executable by the shell, possibly followed by an non-escaped percentage
+;; sign. The text after the percentage sign is to be fed to the command's
+;; standard input, with further unescaped percents being substituted with
+;; newlines. The escape character can itself be escaped.
+;;
+;; This regexp separates the two halves of the string, and indeed determines if
+;; the second part is present.
+
+(define action-string-regexp (make-regexp "((\\\\%|[^%])*)%(.*)$"))
+
+
+
+;; This regexp identifies an escaped percentage sign.
+
+(define e-percent (make-regexp "\\\\%"))
+
+
+;; Function to execute some action (this may be a shell command, lamdba function
+;; or list of scheme procedures) in a forked process, with the input coming from
+;; the string, and output (including the error output) being sent to a pipe
+;; opened on a mail transport.
+
+(use-modules (ice-9 popen))
+
+(define (with-mail-out action . user)
+
+  ;; Determine the name of the user who is to recieve the mail, looking for a
+  ;; name in the optional user argument, then in the MAILTO environment
+  ;; variable, and finally in the LOGNAME environment variable. (The case
+  ;; MAILTO="" is dealt with specially below.)
+
+  (let* ((mailto (getenv "MAILTO"))
+         (user (cond (mailto mailto)
+                     ((not (null? user)) (car user))
+                     (else (getenv "LOGNAME"))))
+         (parent->child (pipe))
+         (child->parent (pipe))
+         (child-pid (primitive-fork)))
+
+    
+    ;; The child process. Close redundant ends of pipes, remap the standard
+    ;; streams, and run the action, taking care to chop off the input part of an
+    ;; action string.
+    
+    (if (eqv? child-pid 0)
+        (begin
+          (close (cdr parent->child))
+          (close (car child->parent))
+
+          (dup2 (port->fdes (car parent->child)) 0)
+          (close (car parent->child))
+          (dup2 (port->fdes (cdr child->parent)) 1)
+          (close (cdr child->parent))
+          (dup2 1 2)
+
+          (cond ((string? action)
+                 (let ((match (regexp-exec action-string-regexp action)))
+                   (system (if match
+                               (let ((action (match:substring match 1)))
+                                 (do ((match (regexp-exec e-percent action)
+                                             (regexp-exec e-percent action)))
+                                     ((not match))
+                                   (set! action (string-append
+                                                         (match:prefix match)
+                                                         "%"
+                                                         (match:suffix match))))
+                                 action)
+                               action))))
+              
+                ((procedure? action) (action))
+                ((list? action) (primitive-eval action)))
+
+          (primitive-exit 0)))
+
+
+    ;; The parent process. Get rid of redundant pipe ends.
+
+    (close (car parent->child))
+    (close (cdr child->parent))
+
+
+    ;; Put stuff to child from after '%' in command line, replacing
+    ;; other %'s with newlines. Ugly or what?
+
+    (if (string? action)
+        (let ((port (cdr parent->child))
+              (match (regexp-exec action-string-regexp action)))
+          (if (and match
+                   (match:substring match 3))
+              (with-input-from-string (match:substring match 3)
+                (lambda ()
+                  (let loop ()
+                    (let ((next-char (read-char)))
+                      (if (not (eof-object? next-char))
+                          (cond
+                            ((char=? next-char #\%)
+                             (newline port)
+                             (loop))
+                            ((char=? next-char #\\)
+                             (let ((escape (read-char)))
+                               (if (eof-object? escape)
+                                   (display #\\ port)
+                                   (if (char=? escape #\%)
+                                       (begin
+                                         (display #\% port)
+                                         (loop))
+                                       (begin
+                                         (display #\\ port)
+                                         (display escape port)
+                                         (loop))))))
+                            (else
+                             (display next-char port)
+                             (loop)))))))))))
+
+    
+    ;; So the child process doesn't hang on to its input expecting more stuff.
+    
+    (close (cdr parent->child))
+
+
+    ;; That's got streaming into the child's input out of the way, now we stream
+    ;; the child's output to a mail sink, but only if there is something there
+    ;; in the first place.
+    
+    (if (eof-object? (peek-char (car child->parent)))
+
+        (read-char (car child->parent))
+        
+        (begin
+          (set-current-output-port (if (and (string? mailto)
+                                            (string=? mailto ""))
+                                       (open-output-file "/dev/null")
+                                       (open-output-pipe
+                                          (string-append config-sendmail
+                                                         " "
+                                                         user))))
+          (set-current-input-port (car child->parent))
+          (display "To: ") (display user) (newline)
+          (display "From: mcron") (newline)
+          (display (string-append "Subject: " user "@" (gethostname)))
+          (newline)
+          (newline)
+
+          (do ((next-char (read-char) (read-char)))
+              ((eof-object? next-char))
+            (display next-char))))
+
+    (close (car child->parent))
+
+    (waitpid child-pid)))