Make 'trap' handle a numerical action.

* gash/built-ins/utils.scm (string->nonnegative-integer): New procedure.
* gash/built-ins/trap.scm (main): If the first argument is a number,
treat it as if the action were '-'.

gash/built-ins/trap.scm

@@ -17,6 +17,7 @@
 ;;; along with Gash.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gash built-ins trap)
+  #:use-module (gash built-ins utils)
   #:use-module (gash compat)
   #:use-module (gash environment)
   #:use-module (ice-9 match))
@@ -54,6 +55,8 @@
   (match args
     (() "print")
     (("--" . args) (main args))
+    (((? string->nonnegative-integer n) conditions ...)
+     (apply main (cons "-" args)))
     ((action conditions ..1)
      (let ((handler (action->handler action)))
        (for-each (lambda (condition)

gash/built-ins/utils.scm

@@ -23,6 +23,7 @@
             built-in?
             split-assignment
             string->positive-integer
+            string->nonnegative-integer
             string->exit-status))
 
 ;;; Commentary:
@@ -68,6 +69,14 @@
          (lambda (n)
            (and (exact-integer? n) (> n 0) n))))
 
+(define (string->nonnegative-integer s)
+  "Return the nonnegative integer represented by the string @var{s}.
+If @var{s} does not represent a nonnegative, decimal integer return
+@code{#f}."
+  (and=> (and (string-every char-set:ascii-digit s) (string->number s))
+         (lambda (n)
+           (and (exact-integer? n) (>= n 0) n))))
+
 (define (string->exit-status s)
   "Return the exit status represented by the string @var{s}.  If
 @var{s} does not represent an exit status (a decimal integer from 0 to