Plan 9's rc.

not a clear win over byron's,
but at least it has the right syntax.

src/cmd/rc/trap.c

@@ -0,0 +1,34 @@
+#include "rc.h"
+#include "exec.h"
+#include "fns.h"
+#include "io.h"
+extern char *Signame[];
+void dotrap(void){
+	register int i;
+	register struct var *trapreq;
+	register struct word *starval;
+	starval=vlook("*")->val;
+	while(ntrap) for(i=0;i!=NSIG;i++) while(trap[i]){
+		--trap[i];
+		--ntrap;
+		if(getpid()!=mypid) Exit(getstatus());
+		trapreq=vlook(Signame[i]);
+		if(trapreq->fn){
+			start(trapreq->fn, trapreq->pc, (struct var *)0);
+			runq->local=newvar(strdup("*"), runq->local);
+			runq->local->val=copywords(starval, (struct word *)0);
+			runq->local->changed=1;
+			runq->redir=runq->startredir=0;
+		}
+		else if(i==SIGINT || i==SIGQUIT){
+			/*
+			 * run the stack down until we uncover the
+			 * command reading loop.  Xreturn will exit
+			 * if there is none (i.e. if this is not
+			 * an interactive rc.)
+			 */
+			while(!runq->iflag) Xreturn();
+		}
+		else Exit(getstatus());
+	}
+}