[postgresql] How to display the function, procedure, triggers source code in postgresql?

Here are few examples from PostgreSQL-9.5

Display list:

  1. Functions: \df+
  2. Triggers : \dy+

Display Definition:

postgres=# \sf
function name is required

postgres=# \sf pg_reload_conf()
CREATE OR REPLACE FUNCTION pg_catalog.pg_reload_conf()
 RETURNS boolean
 LANGUAGE internal
 STRICT
AS $function$pg_reload_conf$function$

postgres=# \sf pg_encoding_to_char
CREATE OR REPLACE FUNCTION pg_catalog.pg_encoding_to_char(integer)
 RETURNS name
 LANGUAGE internal
 STABLE STRICT
AS $function$PG_encoding_to_char$function$