add an example of docker ps, and also of link aliases

docs/sources/commandline/cli.rst

@@ -799,6 +799,15 @@ Known Issues (kill)
       -notrunc=false: Don't truncate output
       -q=false: Only display numeric IDs
 
+Running ``docker ps`` showing 2 linked containers.
+
+.. code-block:: bash
+
+    $ docker ps
+    CONTAINER ID        IMAGE                        COMMAND                CREATED              STATUS              PORTS               NAMES
+    4c01db0b339c        ubuntu:12.04                 bash                   17 seconds ago       Up 16 seconds                           webapp              
+    d7886598dbe2        crosbymichael/redis:latest   /redis-server --dir    33 minutes ago       Up 33 minutes       6379/tcp            redis,webapp/db     
+
 .. _cli_pull:
 
 ``pull``