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Diffstat (limited to 'vixie.scm')
| -rw-r--r-- | vixie.scm | 481 |
1 files changed, 0 insertions, 481 deletions
diff --git a/vixie.scm b/vixie.scm deleted file mode 100644 index 662a194..0000000 --- a/vixie.scm +++ /dev/null @@ -1,481 +0,0 @@ -;; Copyright (C) 2003 Dale Mellor -;; -;; This program 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 2, or (at your option) -;; any later version. -;; -;; This program 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 this program; if not, write to the Free Software -;; Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA 02111-1307, -;; USA. - - - -;; This file provides 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. - - - -(use-modules (ice-9 regex) (ice-9 rdelim) - (srfi srfi-1) (srfi srfi-13) (srfi srfi-14)) - - - -;; In Vixie-style time specifications three-letter symbols are allowed to stand -;; for the numbers corresponding to months and days of the week. We deal with -;; this by making a textual substitution early on in the processing of the -;; strings. -;; -;; We start by defining, once and for all, a list of cons cells consisting of -;; regexps which will match the symbols - which allow an arbitrary number of -;; other letters to appear after them (so that the user can optionally complete -;; the month and day names; this is an extension of Vixie) - and the value which -;; is to replace the symbol. -;; -;; The procedure then takes a string, and then for each symbol in the -;; parse-symbols list attempts to locate an instance and replace it with an -;; ASCII representation of the value it stands for. The procedure returns the -;; modified string. (Note that each symbol can appear only once, which meets the -;; Vixie specifications technically but still allows silly users to mess things -;; up). - -(define parse-symbols - (map (lambda (symbol-cell) - (cons (make-regexp (string-append (car symbol-cell) "[[:alpha:]]*") - regexp/icase) - (cdr symbol-cell))) - '(("jan" . "0") ("feb" . "1") ("mar" . "2") ("apr" . "3") - ("may" . "4") ("jun" . "5") ("jul" . "6") ("aug" . "7") - ("sep" . "8") ("oct" . "9") ("nov" . "10") ("dec" . "11") - - ("sun" . "0") ("mon" . "1") ("tue" . "2") ("wed" . "3") - ("thu" . "4") ("fri" . "5") ("sat" . "6") ))) - -(define (vixie-substitute-parse-symbols string) - (for-each (lambda (symbol-cell) - (let ((match (regexp-exec (car symbol-cell) string))) - (if match - (set! string (string-append (match:prefix match) - (cdr symbol-cell) - (match:suffix match)))))) - parse-symbols) - string) - - - -;; A Vixie time specification is made up of a space-separated list of elements, -;; and the elements consist of a comma-separated list of subelements. The -;; procedure below takes a string holding a subelement, which should have no -;; spaces or symbols (see above) in it, and returns a list of all values which -;; that subelement indicates. There are five distinct cases which must be dealt -;; with: [1] a single '*' which returns a list of all values; [2] a '*' followed -;; by a step specifier; [3] a range and step specifier; [4] a range; and [5] a -;; single number. -;; -;; To perform the computation required for the '*' cases, we need to pass the -;; limit of the allowable range for this subelement as the third argument. As -;; days of the month start at 1 while all the other time components start at 0, -;; we must pass the base of the range to deal with this case also. - -(define parse-vixie-subelement-regexp - (make-regexp "^([[:digit:]]+)(-([[:digit:]]+)(/([[:digit:]]+))?)?$")) - -(define (parse-vixie-subelement string base limit) - (if (char=? (string-ref string 0) #\*) - (range base limit (if (> (string-length string) 1) - (string->number (substring string 2)) ;; [2] - 1)) ;; [1] - (let ((match (regexp-exec parse-vixie-subelement-regexp string))) - (cond ((not match) - (display "Error: Bad Vixie-style time specification.\n") - (primitive-exit 9)) - ((match:substring match 5) - (range (string->number (match:substring match 1)) - (+ 1 (string->number (match:substring match 3))) - (string->number (match:substring match 5)))) ;; [3] - ((match:substring match 3) - (range (string->number (match:substring match 1)) - (+ 1 (string->number (match:substring match 3))))) ;; [4] - (else - (list (string->number (match:substring match 1)))))))) ;; [5] - - - -;; A Vixie element contains the entire specification, without spaces or symbols, -;; of the acceptable values for one of the time components (minutes, hours, -;; days, months, week days). Here we break the comma-separated list into -;; subelements, and process each with the procedure above. The return value is a -;; list of all the valid values of all the subcomponents. -;; -;; The second and third arguments are the base and upper limit on the values -;; that can be accepted for this time element. -;; -;; The effect of the 'apply append' is to merge a list of lists into a single -;; list. - -(define (parse-vixie-element string base limit) - (apply append - (map (lambda (sub-element) - (parse-vixie-subelement sub-element base limit)) - (string-tokenize string (char-set-complement (char-set #\,)))))) - - - -;; Consider there are two lists, one of days in the month, the other of days in -;; the week. This procedure returns an augmented list of days in the month with -;; weekdays accounted for. - -(define (interpolate-weekdays mday-list wday-list month year) - (let ((t (localtime 0))) - (set-tm:mday t 1) - (set-tm:mon t month) - (set-tm:year t year) - (let ((first-day (tm:wday (cdr (mktime t))))) - (apply append - mday-list - (map (lambda (wday) - (let ((first (- wday first-day))) - (if (< first 0) (set! first (+ first 7))) - (range (+ 1 first) 32 7))) - wday-list))))) - - - -;; Return the number of days in a month. Fix up a tm object for the zero'th day -;; of the next month, rationalize the object and extract the day. - -(define (days-in-month month year) - (let ((t (localtime 0))) (set-tm:mday t 0) - (set-tm:mon t (+ month 1)) - (set-tm:year t year) - (tm:mday (cdr (mktime t))))) - - - -;; We will be working with a list of time-spec's, one for each element of a time -;; specification (minute, hour, ...). Each time-spec holds three pieces of -;; information: a list of acceptable values for this time component, a procedure -;; to get the component from a tm object, and a procedure to set the component -;; in a tm object. - -(define (time-spec:list time-spec) (vector-ref time-spec 0)) -(define (time-spec:getter time-spec) (vector-ref time-spec 1)) -(define (time-spec:setter time-spec) (vector-ref time-spec 2)) - - - -;; This procedure modifies the time tm object by setting the component referred -;; to by the time-spec object to its next acceptable value. If this value is not -;; greater than the original (because we have wrapped around the top of the -;; acceptable values list), then the function returns #t, otherwise it returns -;; #f. Thus, if the return value is true then it will be necessary for the -;; caller to increment the next coarser time component as well. -;; -;; The first part of the let block is a concession to humanity; the procedure is -;; simply unreadable without all of these aliases. - -(define (increment-time-component time time-spec) - (let* ((time-list (time-spec:list time-spec)) - (getter (time-spec:getter time-spec)) - (setter (time-spec:setter time-spec)) - (next-best (find-best-next (getter time) time-list)) - (wrap-around (eqv? (cdr next-best) 9999))) - (setter time ((if wrap-around car cdr) next-best)) - wrap-around)) - - - -;; There now follows a set of procedures for adjusting an element of time, -;; i.e. taking it to the next acceptable value. In each case, the head of the -;; time-spec-list is expected to correspond to the component of time in -;; question. If the adjusted value wraps around its allowed range, then the next -;; biggest element of time must be adjusted, and so on. - -;; There is no specification allowed for the year component of -;; time. Therefore, if we have to make an adjustment (presumably because a -;; monthly adjustment has wrapped around the top of its range) we can simply -;; go to the next year. - -(define (nudge-year! time) - (set-tm:year time (+ (tm:year time) 1))) - - -;; We nudge the month by finding the next allowable value, and if it wraps -;; around we also nudge the year. The time-spec-list will have time-spec -;; objects for month and weekday. - -(define (nudge-month! time time-spec-list) - (and (increment-time-component time (car time-spec-list)) - (nudge-year! time))) - - -;; Try to increment the day component of the time according to the combination -;; of the mday-list and the wday-list. If this wraps around the range, or if -;; this falls outside the current month (31st February, for example), then -;; bump the month, set the day to zero, and recurse on this procedure to find -;; the next day in the new month. -;; -;; The time-spec-list will have time-spec entries for mday, month, and -;; weekday. - -(define (nudge-day! time time-spec-list) - (if (or (increment-time-component - time - (vector - (interpolate-weekdays (time-spec:list (car time-spec-list)) - (time-spec:list (caddr time-spec-list)) - (tm:mon time) - (tm:year time)) - tm:mday - set-tm:mday)) - (> (tm:mday time) (days-in-month (tm:mon time) (tm:year time)))) - (begin - (nudge-month! time (cdr time-spec-list)) - (set-tm:mday time 0) - (nudge-day! time time-spec-list)))) - - - -;; The hour is bumped to the next accceptable value, and the day is bumped if -;; the hour wraps around. -;; -;; The time-spec-list holds specifications for hour, mday, month and weekday. - -(define (nudge-hour! time time-spec-list) - (and (increment-time-component time (car time-spec-list)) - (nudge-day! time (cdr time-spec-list)))) - - - -;; The minute is bumped to the next accceptable value, and the hour is bumped -;; if the minute wraps around. -;; -;; The time-spec-list holds specifications for minute, hour, day-date, month -;; and weekday. - -(define (nudge-min! time time-spec-list) - (and (increment-time-component time (car time-spec-list)) - (nudge-hour! time (cdr time-spec-list)))) - - - - -;; This is a procedure which returns a procedure which computes the next time a -;; command should run after the current time, based on the information in the -;; Vixie-style time specification. -;; -;; We start by computing a list of time-spec objects (described above) for the -;; minute, hour, date, month, year and weekday components of the overall time -;; specification [1]. When we create the return procedure, it is this list to -;; which references to a time-spec-list will be bound. It will be used by the -;; returned procedure [3] to compute the next time a function should run. Any -;; 7's in the weekday component of the list (the last one) are folded into 0's -;; (both values represent sunday) [2]. Any 0's in the month-day component of the -;; list are removed (this allows a solitary zero to be used to indicate that -;; jobs should only run on certain days of the _week_) [2.1]. -;; -;; The returned procedure itself:- -;; -;; Starts by obtaining the current broken-down time [4], and fixing it to -;; ensure that it is an acceptable value, as follows. Each component from the -;; biggest down is checked for acceptability, and if it is not acceptable it -;; is bumped to the next acceptable value (this may cause higher components to -;; also be bumped if there is range wrap-around) and all the lower components -;; are set to -1 so that it can successfully be bumped up to zero if this is -;; an allowed value. The -1 value will be bumped up subsequently to an allowed -;; value [5]. -;; -;; Once it has been asserted that the current time is acceptable, or has been -;; adjusted to one minute before the next acceptable time, the minute -;; component is then bumped to the next acceptable time, which may ripple -;; through the higher components if necessary [6]. We now have the next time -;; the command needs to run. -;; -;; The new time is then converted back into a UNIX time, and returned [7]. - -(define (parse-vixie-time string) - (let* ((tokens (string-tokenize (vixie-substitute-parse-symbols string))) - (time-spec-list - (map-in-order (lambda (x) (vector (parse-vixie-element - (list-ref tokens (vector-ref x 0)) - (vector-ref x 1) - (vector-ref x 2)) - (vector-ref x 3) - (vector-ref x 4))) - ;; token range-top+1 getter setter - `( #( 0 0 60 ,tm:min ,set-tm:min ) - #( 1 0 24 ,tm:hour ,set-tm:hour ) - #( 2 1 32 ,tm:mday ,set-tm:mday ) - #( 3 0 12 ,tm:mon ,set-tm:mon ) - #( 4 0 7 ,tm:wday ,set-tm:wday ))))) ;; [1] - - (vector-set! (car (last-pair time-spec-list)) - 0 - (map (lambda (time-spec) - (if (eqv? time-spec 7) 0 time-spec)) - (vector-ref (car (last-pair time-spec-list)) 0))) ;; [2] - - (vector-set! (caddr time-spec-list) - 0 - (remove (lambda (day) (eqv? day 0)) - (vector-ref (caddr time-spec-list) 0))) ;; [2.1] - - - (lambda (current-time) ;; [3] - (let ((time (localtime current-time))) ;; [4] - - (if (not (member (tm:mon time) - (time-spec:list (cadddr time-spec-list)))) - (begin - (nudge-month! time (cdddr time-spec-list)) - (set-tm:mday time 0))) - (if (or (eqv? (tm:mday time) 0) - (not (member (tm:mday time) - (interpolate-weekdays - (time-spec:list (caddr time-spec-list)) - (time-spec:list (caddr (cddr time-spec-list))) - (tm:mon time) - (tm:year time))))) - (begin - (nudge-day! time (cddr time-spec-list)) - (set-tm:hour time -1))) - (if (not (member (tm:hour time) - (time-spec:list (cadr time-spec-list)))) - (begin - (nudge-hour! time (cdr time-spec-list)) - (set-tm:min time -1))) ;; [5] - - (set-tm:sec time 0) - (nudge-min! time time-spec-list) ;; [6] - - (car (mktime time)))))) ;; [7] - - - - -;; 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) (begin (display "Bad job line in Vixie file.\n") - (primitive-exit 10))) - (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:]]+(.*)$"))) - -(define (parse-system-vixie-line line) - (let ((match (regexp-exec parse-system-vixie-line-regexp line))) - (if (not match) (begin (display "Bad job line in /etc/crontab.\n") - (primitive-exit 11))) - (set! configuration-user (getpw (match:substring match 3))) - (job (match:substring match 1) - (lambda () (with-mail-out (match:substring match 4) - (passwd:name configuration-user))) - (match:substring match 4)))) - - - - -;; The next procedure reads an entire Vixie-style file. For each line in the -;; file there are three possibilities (after continuation lines have been -;; appended): the line is blank or contains only a comment, the line contains an -;; environment modifier which will be handled in environment.scm, or the line -;; contains a command specification in which case we use the procedure above to -;; add an entry to the internal job list. -;; -;; Note that the environment modifications are cleared, so that there is no -;; interference between crontab files (this might lead to unpredictable -;; behaviour because the order in which crontab files are processed, if there is -;; more than one, is generally undefined). - -(define read-vixie-file-comment-regexp - (make-regexp "^[[:space:]]*(#.*)?$")) - - -(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))) - ((eof-object? line)) - - ;; 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 - (string-append - (substring line 0 (- (string-length line) 1)) - next-line)))) - - ;; 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)))))) - - - -;; 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 - (begin - (if (null? parse-vixie-line) - (read-vixie-port port) - (read-vixie-port port (car parse-vixie-line))) - (close port))))) - - - -;; 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 "/var/cron/socket") - (display "/etc/crontab" socket) - (close socket))))))) |