diff -r 3057f813da14 tools/examples/block
--- a/tools/examples/block	Thu Nov 29 19:30:33 2007 +0000
+++ b/tools/examples/block	Wed Dec 05 23:56:03 2007 +0900
@@ -220,6 +220,7 @@ case "$command" in
         # Canonicalise the file, for sharing check comparison, and the mode
         # for ease of use here.
         file=$(readlink -f "$p") || fatal "$p does not exist."
+        test -f "$file" || fatal "$file does not exist."
         mode=$(canonicalise_mode "$mode")
 
         claim_lock "block"