Plan 9's rc.

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

src/cmd/rc/io.h

@@ -0,0 +1,24 @@
+#define	EOF	(-1)
+#define	NBUF	512
+struct io{
+	int fd;
+	char *bufp, *ebuf, *strp, buf[NBUF];
+};
+io *err;
+io *openfd(int), *openstr(void), *opencore(char *, int);
+int emptybuf(io*);
+void pchr(io*, int);
+int rchr(io*);
+void closeio(io*);
+void flush(io*);
+int fullbuf(io*, int);
+void pdec(io*, long);
+void poct(io*, ulong);
+void phex(io*, long);
+void pquo(io*, char*);
+void pwrd(io*, char*);
+void pstr(io*, char*);
+void pcmd(io*, tree*);
+void pval(io*, word*);
+void pfnc(io*, thread*);
+void pfmt(io*, char*, ...);