Add tcs; it compiles in my world, but I haven't tried it in Russ's yet.

src/cmd/pbd.c

@@ -0,0 +1,19 @@
+#include <u.h>
+#include <libc.h>
+
+void
+main(void)
+{
+	char buf[512], *p;
+
+	p = "???";
+	if(getwd(buf, sizeof buf)){
+		p = strrchr(buf, '/');
+		if(p == nil)
+			p = buf;
+		else if(p>buf || p[1]!='\0')
+			p++;
+	}
+	write(1, p, strlen(p));
+	exits(0);
+}