To use client certs you need to set cert for auth-method for a particular connection. So to not use them and have an ssl connection set the connection type to hostssl and set auth-method to something other then cert.
I am using linux as a clinet machine and want to connect through command line, without client certificate in encrypted format or on SSL. What should I do?
If I understand, you want to a non-ssl connection to Postgres, correct?
If so then per the docs in the above link then use host for either local or remote TCP/IP connections or local for a socket connection.