mcron: Handle command line arguments in C with argp

'argp' is a convenient and maintainable way to parse command line arguments.
Guile doesn't offer an equivalent of this, so the command line handling has
been moved to C.

* src/mcron.c (parse_args, parse_opt): New functions.
(inner_main): Call 'parse_args'.
* src/mcron/scripts/mcron.scm (show-help, %options): Delete.
(main): Remove command line handling.

src/mcron.c

@@ -18,10 +18,13 @@
    along with GNU Mcron.  If not, see <http://www.gnu.org/licenses/>.  */
 
 #include "utils.h"
+#include <argp.h>
 #include <libguile.h>
 
 /* Forward declarations.  */
 static void inner_main (void *closure, int argc, char *argv[]);
+static SCM parse_args (int argc, char *argv[]);
+static error_t parse_opt (int key, char *arg, struct argp_state *state);
 
 int
 main (int argc, char *argv[])
@@ -44,6 +47,83 @@ main (int argc, char *argv[])
 static void
 inner_main (void *closure, int argc, char *argv[])
 {
+  SCM config = parse_args (argc, argv);
   scm_set_current_module (scm_c_resolve_module ("mcron scripts mcron"));
-  scm_call_0 (scm_variable_ref (scm_c_lookup ("main")));
+  scm_call_1 (scm_variable_ref (scm_c_lookup ("main")), config);
+}
+
+/* Handle command line arguments.  */
+static SCM
+parse_args (int argc, char *argv[])
+{
+  static struct argp_option options[] = {
+    {"schedule", 's', "N", 0,
+     "Display the next N jobs that will be run"},
+    {"daemon", 'd', 0, 0,
+     "Run as a daemon process"},
+    {"stdin", 'i', "FORMAT", 0,
+     "Format of data passed as standard input or file arguments (default guile)"},
+    {0, 0, 0, 0, 0}
+  };
+
+  static struct argp argp = {
+    .options = options,
+    .parser = parse_opt,
+    .args_doc = "[FILE...]",
+    .doc = "Run an mcron process according to the specifications in the "
+    "FILE... (`-' for standard input), or use all the files in "
+    "~/.config/cron (or the deprecated ~/.cron) with .guile or "
+    ".vixie extensions."
+  };
+
+  SCM config = SCM_EOL;
+  argp_program_version = PACKAGE_STRING;
+  argp_program_bug_address = PACKAGE_BUGREPORT;
+  argp_parse (&argp, argc, argv, 0, NULL, &config);
+
+  return config;
+}
+
+static error_t
+parse_opt (int key, char *arg, struct argp_state *state)
+{
+  SCM *config = state->input;
+
+  switch (key)
+    {
+    case 's':
+      *config = scm_assq_set_x (*config, scm_from_utf8_symbol ("schedule"),
+                                scm_from_int (atoi (arg)));
+      break;
+    case 'd':
+      *config = scm_assq_set_x (*config, scm_from_utf8_symbol ("daemon"),
+                                SCM_BOOL_T);
+      break;
+    case 'i':
+      if (strncmp (arg, "vixie", 6) == 0)
+        *config = scm_assq_set_x (*config, scm_from_utf8_symbol ("vixie"),
+                                  SCM_BOOL_T);
+      break;
+    case ARGP_KEY_NO_ARGS:
+      *config = scm_assq_set_x (*config, scm_from_utf8_symbol ("files"),
+                                SCM_EOL);
+      break;
+    case ARGP_KEY_ARGS:
+      {
+        SCM lst = SCM_EOL;
+        int filec = state->argc - state->next;
+        char **filev = state->argv + state->next;
+
+        for (int i = filec - 1; i >= 0; i--)
+          lst = scm_cons (scm_from_locale_string (filev[i]), lst);
+
+        *config = scm_assq_set_x (*config, scm_from_utf8_symbol ("files"),
+                                  lst);
+        break;
+      }
+    case ARGP_KEY_ARG:
+    default:
+      return ARGP_ERR_UNKNOWN;
+    }
+  return 0;
 }

src/mcron/scripts/mcron.scm

@@ -25,34 +25,6 @@
   #:use-module (mcron vixie-specification)
   #:export (main))
 
-(define (show-help)
-  (display "Usage: mcron [OPTIONS] [FILES]
-Run an mcron process according to the specifications in the FILES (`-' for
-standard input), or use all the files in ~/.config/cron (or the
-deprecated ~/.cron) with .guile or .vixie extensions.
-
-  -v, --version             Display version
-  -h, --help                Display this help message
-  -sN, --schedule[=]N       Display the next N jobs that will be run by mcron
-  -d, --daemon              Immediately detach the program from the terminal
-                              and run as a daemon process
-  -i, --stdin=(guile|vixie) Format of data passed as standard input or
-                              file arguments (default guile)")
-  (newline)
-  (show-package-information))
-
-(define %options
-  `((schedule (single-char #\s) (value #t)
-              (predicate ,(λ (str) (string->number str))))
-    (daemon   (single-char #\d) (value #f))
-    (noetc    (single-char #\n) (value #f))
-    (stdin    (single-char #\i) (value #t)
-              (predicate ,(λ (val)
-                            (or (string=? val "guile")
-                                (string=? val "vixie")))))
-    (version  (single-char #\v) (value #f))
-    (help     (single-char #\h) (value #f))))
-
 (define process-user-file
   (let ((guile-regexp (make-regexp "\\.gui(le)?$"))
         (vixie-regexp (make-regexp "\\.vix(ie)?$")))
@@ -102,35 +74,30 @@ $XDG_CONFIG_HOME is not defined uses ~/.config/cron instead)."
 ;;; Entry point.
 ;;;
 
-(define* (main #:optional (args (command-line)))
+(define* (main #:optional (opts '()))
-  (let ((opts (parse-args args %options)))
+  (when config-debug
-    (when config-debug
+    (debug-enable 'backtrace))
-      (debug-enable 'backtrace))
+
-    (cond ((option-ref opts 'help #f)
+  (%process-files (or (assq-ref opts 'files) '())
-           (show-help)
+                  (if (assq-ref opts 'vixie) "vixie" "guile"))
-           (exit 0))
+
-          ((option-ref opts 'version #f)
+  (cond ((assq-ref opts 'schedule) ;display jobs schedule
-           (show-version "mcron")
+         => (λ (count)
-           (exit 0))
+              (display (get-schedule (max 1 count)))
-          (else
+              (exit 0)))
-           (%process-files (option-ref opts '() '())
+        ((assq-ref opts 'daemon) ;run mcron as a daemon
-                           (option-ref opts 'stdin "guile"))
+         (case (primitive-fork)
-           (cond ((option-ref opts 'schedule #f) ;display jobs schedule
+           ((0)  (setsid))
-                  => (λ (count)
+           (else (exit 0)))))
-                       (display (get-schedule (max 1 (string->number count))))
+
-                       (exit 0)))
+  ;; Forever execute the 'run-job-loop', and when it drops out (can
-                 ((option-ref opts 'daemon #f) ;run mcron as a daemon
+  ;; only be because a message has come in on the socket) we process
-                  (case (primitive-fork)
+  ;; the socket request before restarting the loop again.
-                    ((0)  (setsid))
+  (catch-mcron-error
-                    (else (exit 0)))))
+   (let ((fdes-list '()))
-           ;; Forever execute the 'run-job-loop', and when it drops out (can
+     (while #t
-           ;; only be because a message has come in on the socket) we process
+       (run-job-loop fdes-list)
-           ;; the socket request before restarting the loop again.
+       ;; we can also drop out of run-job-loop because of a SIGCHLD,
-           (catch-mcron-error
+       ;; so must test FDES-LIST.
-            (let ((fdes-list '()))
+       (unless (null? fdes-list)
-              (while #t
+         (process-update-request fdes-list))))))
-                (run-job-loop fdes-list)
-                ;; we can also drop out of run-job-loop because of a SIGCHLD,
-                ;; so must test FDES-LIST.
-                (unless (null? fdes-list)
-                  (process-update-request fdes-list)))))))))