use macro for /usr/local/plan9
diff --git a/man/man4/ramfs.4 b/man/man4/ramfs.4
index 32405de..25ae4bf 100644
--- a/man/man4/ramfs.4
+++ b/man/man4/ramfs.4
@@ -44,7 +44,7 @@
 to write a user-level file server.
 It can also be used to provide high-performance temporary files.
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/ramfs.c
+.B \*9/src/cmd/ramfs.c
 .SH "SEE ALSO"
 .IR 9p (3),
 .IR 9pserve (4)