use macro for /usr/local/plan9
diff --git a/man/man1/fsize.1 b/man/man1/fsize.1
index cabe7f3..dd2da56 100644
--- a/man/man1/fsize.1
+++ b/man/man1/fsize.1
@@ -15,8 +15,8 @@
 prints the name and modification time (in seconds since the epoch)
 of each of the files.
 .SH SOURCE
-.B /usr/local/plan9/src/cmd/fsize.c
+.B \*9/src/cmd/fsize.c
 .br
-.B /usr/local/plan9/src/cmd/mtime.c
+.B \*9/src/cmd/mtime.c
 .SH BUGS
 The output formats of the two programs are different.