tools: ndnsec-delete reports success or failure

Change-Id: I9b53fcc030fbca34acdf0c7dc3afc8ae8e8d523d
Refs: #2275
diff --git a/docs/manpages/ndnsec-delete.rst b/docs/manpages/ndnsec-delete.rst
index e501592..3c808af 100644
--- a/docs/manpages/ndnsec-delete.rst
+++ b/docs/manpages/ndnsec-delete.rst
@@ -18,6 +18,7 @@
 all the keys and certificates belonging to the identity will be deleted as well. If a key is
 deleted,  all the certificate belonging to the key will be deleted as well.
 
+
 Options
 -------
 
@@ -27,6 +28,13 @@
 ``-c``
   Interpret ``name`` as a certificate name and delete the certificate.
 
+Exit Status
+-----------
+
+Normally, the exit status is 0 if the requested entity is deleted successfully.
+If the entity to be deleted does not exist, the exit status is 1.
+For other errors, the exit status is 2.
+
 Examples
 --------