Add the trap built-in

* geesh/built-ins/trap.scm: New file.
* Makefile.am: Add it.
* geesh/built-ins.scm (*special-built-ins*): Add trap.

Makefile.am

@@ -58,6 +58,7 @@ MODULES =                                       \
   geesh/built-ins/return.scm                    \
   geesh/built-ins/set.scm                       \
   geesh/built-ins/shift.scm                     \
+  geesh/built-ins/trap.scm                      \
   geesh/built-ins/true.scm                      \
   geesh/built-ins/umask.scm                     \
   geesh/built-ins/unset.scm                     \

geesh/built-ins.scm

@@ -45,7 +45,7 @@
     ("set" . ,(@@ (geesh built-ins set) main))
     ("shift" . ,(@@ (geesh built-ins shift) main))
     ("times" . ,undefined)
-    ("trap" . ,undefined)
+    ("trap" . ,(@@ (geesh built-ins trap) main))
     ("unset" . ,(@@ (geesh built-ins unset) main))))
 
 ;; Regular built-ins take precendence over utilities in the search

geesh/built-ins/trap.scm

@@ -0,0 +1,67 @@
+;;; The Geesh Shell Interpreter
+;;; Copyright 2018 Timothy Sample <samplet@ngyro.com>
+;;;
+;;; This file is part of Geesh.
+;;;
+;;; Geesh 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.
+;;;
+;;; Geesh 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 Geesh.  If not, see <http://www.gnu.org/licenses/>.
+
+(define-module (geesh built-ins trap)
+  #:use-module (geesh environment)
+  #:use-module (ice-9 match))
+
+;;; Commentary:
+;;;
+;;; The 'trap' utility.
+;;;
+;;; Code:
+
+(define sh:eval (@@ (geesh built-ins eval) main))
+
+(define (action->handler action)
+  (let ((n (string->number action)))
+    (cond
+     ((and n (integer? n) (>= n 0)) SIG_DFL)
+     ((string=? action "-") SIG_DFL)
+     ((string-null? action) SIG_IGN)
+     (else (lambda () (sh:eval action))))))
+
+(define (condition->signum condition)
+  (let ((n (string->number condition)))
+    (cond
+     ((and n (integer? n)) n)
+     ((string-ci=? condition "EXIT") 0)
+     (else (let* ((name (if (string-prefix-ci? "SIG" condition)
+                            (string-upcase condition)
+                            (string-append "SIG" (string-upcase condition))))
+                  (symb (string->symbol name)))
+             (or (and=> (module-variable (current-module) symb)
+                        variable-ref)
+                 -1))))))
+
+(define (main . args)
+  (match args
+    (() "print")
+    (("--" . args) (main args))
+    ((action conditions ..1)
+     (let ((handler (action->handler action)))
+       (for-each (lambda (condition)
+                   (match (condition->signum condition)
+                     (0 (set-atexit! handler))
+                     (n (sigaction n handler))))
+                 conditions))
+     EXIT_SUCCESS)
+    (_ (format (current-error-port)
+               "~a: trap: Invalid options ~s.~%"
+               (car (program-arguments)) args)
+       EXIT_FAILURE)))