Give mcron --log option to turn logging on.

This makes the behaviour backwards compatible with all previous uses of mcron.

* src/mcron/base.scm: establish %do-logging parameter and act on it
* src/mcron/scripts/mcron.scm: set %do-logging according to command line
* tests/base.scm: some tests require %do-logging to be set

src/mcron/base.scm

@@ -45,6 +45,7 @@
             display-schedule
             run-job-loop
 
+            %do-logging
             %date-format
             %log-format
             validate-date-format
@@ -85,6 +86,8 @@
   (user    schedule-user    set-schedule-user!)     ;list of <job>
   (current schedule-current set-schedule-current!)) ;symbol 'user or 'system
 
+(define %do-logging (make-parameter #f))
+
 ;; A (srfi srfi-19) format string for the date.  It is used to format the
 ;; timestamp argument.  Defaults to the local ISO-8601 date/time format.
 (define %date-format (make-parameter "~5"))
@@ -284,7 +287,8 @@ streams can be read as well as the name of the job."
      ;; Execute the action.
      (catch #t
        (lambda ()
-         (format #t "running...~%")
+         (if (%do-logging)
+             (format #t "running...~%"))
          (flush-all-ports)
          (let* ((result ((job:action job)))
                 (exit-val/maybe (false-if-exception
@@ -292,7 +296,8 @@ streams can be read as well as the name of the job."
            (when (and exit-val/maybe
                       (not (= 0 exit-val/maybe)))
              (error "unclean exit status" exit-val/maybe)))
-         (format #t "completed in ~,3fs~%" (seconds-since start))
+         (if (%do-logging)
+             (format #t "completed in ~,3fs~%" (seconds-since start)))
          (flush-all-ports)
          (primitive-exit 0))
        (lambda args
@@ -354,7 +359,11 @@ associated <job-data> instance."
             (cons 'suspended partial-continuation))))
 
       (define (format-line line)
-        (format #t "~@?" (%log-format) timestamp pid name line))
+        (cond ((%do-logging)
+               (format #t "~@?" (%log-format) timestamp pid name line))
+              ((and (string? line)
+                    (not (string-null? line)))
+               (display line))))
 
       (let loop ((line+delim (read-line*)))
         (match line+delim
@@ -367,8 +376,10 @@ associated <job-data> instance."
           (("" . #\cr)
            ;; A carriage return directly followed a delimiter.  Ignore it.
            (loop (read-line*)))
-          ((line . _)
-           (format-line line)
+          ((line . delim)
+           (format-line (if (%do-logging)
+                            line
+                            (string-append line (string delim))))
            (loop (read-line*)))))))
 
   (for-each log-data

src/mcron/scripts/mcron.scm

@@ -42,6 +42,7 @@ standard input), or use all the files in ~/.config/cron (or the deprecated
   -i, --stdin=(guile|vixie)  Format of data passed as standard input
                              (default guile)
   -s, --schedule[=N]         Display the next N (or 8) jobs that will be run
+  -l, --log                  Write log messages to standard output
   --log-format=FMT           (ice-9 format) format string for log messages
   --date-format=FMT          (srfi srfi-19) date format string for log messages
   -?, --help                 Give this help list
@@ -122,6 +123,7 @@ directory. Double-check the folder and file permissions and syntax."))))
                                                     (string=? in "vixie")))))
                   (schedule (single-char #\s) (value optional)
                             (predicate ,string->number))
+                  (log (single-char #\l) (value #f))
                   (log-format  (value #t) (predicate ,validate-log-format))
                   (date-format (value #t) (predicate ,validate-date-format))
                   (help     (single-char #\?))
@@ -147,6 +149,7 @@ directory. Double-check the folder and file permissions and syntax."))))
                      (else (exit 0)))))
 
     (parameterize
-        ((%log-format  (option-ref options 'log-format (%log-format)))
+        ((%do-logging (option-ref options 'log (%do-logging)))
+         (%log-format  (option-ref options 'log-format (%log-format)))
          (%date-format (option-ref options 'date-format (%date-format))))
       (run-job-loop))))

tests/base.scm

@@ -234,13 +234,14 @@
           (sigaction SIGCHLD SIG_DFL))))))
 
 (test-assert "run-job, output"
-  (let ((output (dummy-job/capture-output
-                 (lambda ()
-                   (format #t "output line 1~%")
-                   (format #t "output line 2\nand 3~%")
-                   (system "echo poutine")
-                   (format (current-error-port)
-                           "some error~%")))))
+  (let ((output (parameterize ((%do-logging #t))
+                  (dummy-job/capture-output
+                   (lambda ()
+                     (format #t "output line 1~%")
+                     (format #t "output line 2\nand 3~%")
+                     (system "echo poutine")
+                     (format (current-error-port)
+                             "some error~%"))))))
     (assert (string-contains output "dummy: running"))
     (assert (string-contains output "dummy: output line 1"))
     (assert (string-contains output "dummy: and 3"))
@@ -270,7 +271,8 @@
     (const #t)))
 
 (test-assert "run-job, output with custom format"
-  (let ((output (parameterize ((%log-format "the message only: ~3@*~a~%"))
+  (let ((output (parameterize ((%do-logging #t)
+                               (%log-format "the message only: ~3@*~a~%"))
                   (dummy-job/capture-output
                    (lambda ()
                      (format #t "output line 1~%"))))))