The connection service file allows libpq connection parameters to be
   associated with a single service name. That service name can then be
   specified by a libpq connection, and the associated settings will be
   used. This allows connection parameters to be modified without requiring
   a recompile of the libpq application. The service name can also be
   specified using the PGSERVICE environment variable.
  
   The connection service file can be a per-user service file
   at ~/.pg_service.conf or the location
   specified by the environment variable PGSERVICEFILE,
   or it can be a system-wide file
   at `pg_config --sysconfdir`/pg_service.conf or in the directory
   specified by the environment variable
   PGSYSCONFDIR.  If service definitions with the same
   name exist in the user and the system file, the user file takes
   precedence.
  
The file uses an “INI file” format where the section name is the service name and the parameters are connection parameters; see Section 34.1.2 for a list. For example:
# comment [mydb] host=somehost port=5433 user=admin
   An example file is provided at
   share/pg_service.conf.sample.