use macro for /usr/local/plan9
diff --git a/man/man3/getwd.3 b/man/man3/getwd.3
index d9aa02b..b68eea4 100644
--- a/man/man3/getwd.3
+++ b/man/man3/getwd.3
@@ -21,7 +21,7 @@
 .I size
 bytes in the buffer provided.
 .SH SOURCE
-.B /usr/local/plan9/src/lib9/getwd.c
+.B \*9/src/lib9/getwd.c
 .SH "SEE ALSO"
 .IR pwd (1),
 .SH DIAGNOSTICS