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Diffstat (limited to 'src/mcron/vixie-specification.scm')
| -rw-r--r-- | src/mcron/vixie-specification.scm | 205 |
1 files changed, 205 insertions, 0 deletions
diff --git a/src/mcron/vixie-specification.scm b/src/mcron/vixie-specification.scm new file mode 100644 index 0000000..cf2679a --- /dev/null +++ b/src/mcron/vixie-specification.scm @@ -0,0 +1,205 @@ +;;;; vixie-specification.scm -- read Vixie-sytle configuration file +;;; Copyright © 2003 Dale Mellor <dale_mellor@users.sourceforge.net> +;;; +;;; 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/>. + +;;;; Commentary: +;;; +;;; Methods for reading a complete Vixie-style configuration file, either from +;;; a real file or an already opened port. It also exposes the method for +;;; parsing the time-specification part of a Vixie string, so that these can +;;; be used to form the next-time-function of a job in a Guile configuration +;;; file. +;;; +;;;; Code: + +(define-module (mcron vixie-specification) + #:use-module (ice-9 regex) + #:use-module (ice-9 rdelim) + #:use-module (mcron base) + #:use-module (mcron config) + #:use-module (mcron job-specifier) + #:use-module (mcron redirect) + #:use-module (mcron vixie-time) + #:use-module (srfi srfi-1) + #:export (parse-user-vixie-line + parse-system-vixie-line + read-vixie-port + read-vixie-file + check-system-crontab)) + +;; A line in a Vixie-style crontab file which gives a command specification +;; carries two pieces of information: a time specification consisting of five +;; space-separated items, and a command which is also separated from the time +;; specification by a space. The line is broken into the two components, and the +;; job procedure run to add the two pieces of information to the job list (this +;; will in turn use the above function to turn the time specification into a +;; function for computing future run times of the command). + +(define parse-user-vixie-line-regexp + (make-regexp "^[[:space:]]*(([^[:space:]]+[[:space:]]+){5})(.*)$")) + +(define (parse-user-vixie-line line) + (let ((match (regexp-exec parse-user-vixie-line-regexp line))) + (if (not match) + (throw 'mcron-error 10 "Bad job line in Vixie file.")) + (job (match:substring match 1) + (lambda () (with-mail-out (match:substring match 3))) + (match:substring match 3)))) + + + +;; The case of reading a line from /etc/crontab is similar to above but the user +;; ID appears in the sixth field, before the action. + +(define parse-system-vixie-line-regexp + (make-regexp (string-append "^[[:space:]]*(([^[:space:]]+[[:space:]]+){5})" + "([[:alpha:]][[:alnum:]_]*)[[:space:]]+(.*)$"))) + +(define (parse-system-vixie-line line) + (let ((match (regexp-exec parse-system-vixie-line-regexp line))) + (if (not match) + (throw 'mcron-error 11 "Bad job line in /etc/crontab.")) + (let ((user (match:substring match 3))) + (set-configuration-user user) + (job (match:substring match 1) + (lambda () (with-mail-out (match:substring match 4) + user)) + (match:substring match 4))))) + + + +;; Procedure to act on an environment variable specification in a Vixie-style +;; configuration file, by adding an entry to the alist above. Returns #t if the +;; operation was successful, #f if the line could not be interpreted as an +;; environment specification. + +(define parse-vixie-environment-regexp1 + (make-regexp + "^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*\"(.*)\"[ \t]*$")) +(define parse-vixie-environment-regexp2 + (make-regexp + "^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*'(.*)'[ \t]*$")) +(define parse-vixie-environment-regexp3 + (make-regexp + "^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*(.*[^ \t])[ \t]*$")) +(define parse-vixie-environment-regexp4 + (make-regexp + "^[ \t]*([[:alpha:]_][[:alnum:]_]*)[ \t]*=[ \t]*$")) + + +(define (parse-vixie-environment string) + (let ((match (or (regexp-exec parse-vixie-environment-regexp1 string) + (regexp-exec parse-vixie-environment-regexp2 string) + (regexp-exec parse-vixie-environment-regexp3 string)))) + (if match + (append-environment-mods (match:substring match 1) + (match:substring match 2)) + (and=> (regexp-exec parse-vixie-environment-regexp4 string) + (λ (match) + (append-environment-mods (match:substring match 1) #f)))))) + +;; The next procedure reads an entire Vixie-style file. For each line in the +;; file there are three possibilities (after continuation lines have been +;; appended): the line is blank or contains only a comment, the line contains an +;; environment modifier which will be handled in the mcron environment module, +;; or the line contains a command specification in which case we use the +;; procedure above to add an entry to the internal job list. +;; +;; Note that the environment modifications are cleared, so that there is no +;; interference between crontab files (this might lead to unpredictable +;; behaviour because the order in which crontab files are processed, if there is +;; more than one, is generally undefined). + +(define read-vixie-file-comment-regexp + (make-regexp "^[[:space:]]*(#.*)?$")) + + +(define (read-vixie-port port . parse-vixie-line) + (clear-environment-mods) + (if port + (let ((parse-vixie-line + (if (null? parse-vixie-line) parse-user-vixie-line + (car parse-vixie-line)))) + (do ((line (read-line port) (read-line port)) + (line-number 1 (1+ line-number))) + ((eof-object? line)) + + (let ((report-line line-number)) + ;; If the line ends with \, append the next line. + (while (and (>= (string-length line) 1) + (char=? (string-ref line + (- (string-length line) 1)) + #\\)) + (let ((next-line (read-line port))) + (if (eof-object? next-line) + (set! next-line "")) + (set! line-number (1+ line-number)) + (set! line + (string-append + (substring line 0 (- (string-length line) 1)) + next-line)))) + + (catch 'mcron-error + (lambda () + ;; Consider the three cases mentioned in the description. + (or (regexp-exec read-vixie-file-comment-regexp line) + (parse-vixie-environment line) + (parse-vixie-line line))) + (lambda (key exit-code . msg) + (throw 'mcron-error exit-code + (apply string-append + (number->string report-line) + ": " + msg))))))))) + + + +;; If a file cannot be opened, we must silently ignore it because it may have +;; been removed by crontab. However, if the file is there it must be parseable, +;; otherwise the error must be propagated to the caller. + +(define (read-vixie-file file-path . parse-vixie-line) + (let ((port #f)) + (catch #t (lambda () (set! port (open-input-file file-path))) + (lambda (key . args) (set! port #f))) + (if port + (catch 'mcron-error + (lambda () + (if (null? parse-vixie-line) + (read-vixie-port port) + (read-vixie-port port (car parse-vixie-line))) + (close port)) + (lambda (key exit-code . msg) + (close port) + (throw 'mcron-error exit-code + (apply string-append file-path ":" msg))))))) + + +;; A procedure which determines if the /etc/crontab file has been recently +;; modified, and, if so, signals the main routine to re-read the file. We run +;; under the with-mail-to command so that the process runs as a child, +;; preventing lockup. If cron is supposed to check for updates to /etc/crontab, +;; then this procedure will be called about 5 seconds before every minute. + +(define (check-system-crontab) + (with-mail-out (lambda () + (let ((mtime (stat:mtime (stat "/etc/crontab")))) + (if (> mtime (- (current-time) 60)) + (let ((socket (socket AF_UNIX SOCK_STREAM 0))) + (connect socket AF_UNIX config-socket-file) + (display "/etc/crontab" socket) + (close socket))))))) |