How to syntax check PostgreSQL config files?

It's bee a long time, but now check is available for pg_hba.conf file:

select pg_hba_file_rules();

Also, you may use pg_file_settings view to define error in postgresql.conf:

select sourcefile, name,sourceline,error from pg_file_settings where error is not null;

example output:

postgres=# select sourcefile, name,sourceline,error from pg_file_settings where error is not null;
               sourcefile               |  name  | sourceline |                error
----------------------------------------+--------+------------+--------------------------------------
 /var/lib/pgsql/11/data/postgresql.conf | lalala |          1 | unrecognized configuration parameter

here I put some bad stuff to check if it's true :)

refer to: https://dba.stackexchange.com/a/151457/177071

you have another approach to test if the config file is correct.

into the command line, type select pg_reload_conf();

postgres=# select pg_reload_conf();
 pg_reload_conf
----------------
 t
(1 row)

This indicates your file is correct. otherwise it would fail.

There is no way to do this that is similar to apache2ctl. If you reload the configuration files and there is a syntax error, the PostgreSQL server will complain in the log and refuse to load the new file. So there is very little risk of messing something up by making a syntax typo. (Of course, this won't guard you against writing semantically wrong things, but apache2ctl won't do that either.) Other than that, it is probably a good idea to test changes in a test server, and have a system that propagates those changes to production in a controlled way.