Allow simpler stdout -f handling.

st.c

@@ -801,12 +801,18 @@ ttynew(void) {
 		close(s);
 		cmdfd = m;
 		signal(SIGCHLD, sigchld);
-		if(opt_io && !(fileio = fopen(opt_io, "w"))) {
+		if(opt_io) {
+			if(!strcmp(opt_io, "-")) {
+				fileio = stdout;
+			} else {
+				if(!(fileio = fopen(opt_io, "w"))) {
 					fprintf(stderr, "Error opening %s:%s\n",
 						opt_io, strerror(errno));
 				}
 			}
 		}
+	}
+}
 
 void
 dump(char c) {