use macro for /usr/local/plan9
diff --git a/man/man1/cat.1 b/man/man1/cat.1
index d2b8d5c..f758beb 100644
--- a/man/man1/cat.1
+++ b/man/man1/cat.1
@@ -83,11 +83,11 @@
 .IR acme (1))
 window.
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/cat.c
+.B \*9/src/cmd/cat.c
 .br
-.B /usr/local/plan9/src/cmd/read.c
+.B \*9/src/cmd/read.c
 .br
-.B /usr/local/plan9/bin/nobs
+.B \*9/bin/nobs
 .SH SEE ALSO
 .IR cp (1)
 .SH DIAGNOSTICS