--- a/Unix.st	Thu Nov 09 12:49:30 1995 +0100
+++ b/Unix.st	Thu Nov 09 14:15:41 1995 +0100
@@ -22,7 +22,7 @@
 COPYRIGHT (c) 1988 by Claus Gittinger
 	     All Rights Reserved
 
-$Header: /cvs/stx/stx/libbasic/Attic/Unix.st,v 1.68 1995-11-09 11:49:30 cg Exp $
+$Header: /cvs/stx/stx/libbasic/Attic/Unix.st,v 1.69 1995-11-09 13:15:41 cg Exp $
 '!
 
 !OperatingSystem primitiveDefinitions!
@@ -48,6 +48,10 @@
 # define WANT_SYSTEM
 #endif
 
+#ifdef ultrix
+# define WANT_SYSTEM
+#endif
+
 #ifdef WANT_REALPATH
 # include <sys/param.h>
 # define _SYS_PARAM_H_INCLUDED_
@@ -269,7 +273,11 @@
 #   define 	__execve	execve
 #   define 	__wait		wait
 #   define 	__waitpid	waitpid
-#   define 	FORK		fork
+#   if defined(ultrix)
+#    define	FORK		vfork
+#   else
+#    define 	FORK		fork
+#   endif
 #  endif /* ! LINUX */
    extern char **environ;
 # endif
@@ -613,7 +621,7 @@
 
 version
 "
-$Header: /cvs/stx/stx/libbasic/Attic/Unix.st,v 1.68 1995-11-09 11:49:30 cg Exp $
+$Header: /cvs/stx/stx/libbasic/Attic/Unix.st,v 1.69 1995-11-09 13:15:41 cg Exp $
 "
 !
 
@@ -4007,17 +4015,18 @@
 executeCommand:aCommandString
     "execute the unix command specified by the argument, aCommandString.
      Return true if successful, false otherwise. 
-     Smalltalk is suspended, while the command is executing.
      The return value of the system()-call is available in the variable
      LastExecStatus (which is zero after successful execution); this value
      consists of the reason for termination (0=normal) in the upper 8bits and,
      iff it was a normal return, the value passed to exit() in the low 8bits."
-
 %{ 
-
     int status;
 
     if (__isString(aCommandString)) {
+	/*
+	 * ST/X provides a modified (fixed) implementation of the
+	 * system() libc-function, which is interruptable ...
+	 */
 # ifdef WANT_SYSTEM
 	__BEGIN_INTERRUPTABLE__
 	status = mySystem((char *) _stringVal(aCommandString));