The ways that psql can be configured to connect to a different port:

  1. compiled in default
  2. PGPORT environment variable
  3. —port or -p option
  4. .pgpass setting

If you are running more than one version of PostgreSQL, you might wonder which one the psql client will talk to by default.

(DJANGO-1-3)bjb@spidy:~$ bash
bjb@spidy:~$ echo $PGPORT

bjb@spidy:~$ unset PGPORT
bjb@spidy:~$ ls -la ~/.pgpass
-rw------- 1 bjb bjb 0 May 20 17:33 /home/bjb/.pgpass
bjb@spidy:~$ locate psql | egrep bin
bjb@spidy:~$ /usr/lib/postgresql/8.4/bin/psql template1
psql (8.4.8)
Type "help" for help.

template1=> \echo :PORT
template1=> \q
bjb@spidy:~$ exit

Voila. The psql in /usr/bin is a perl script wrapper for the real psql. To find the “compiled-in” default port number, you can run the real psql without the command-line arg to change the port number, --port 5555 or -p 5555, and you also need to unset PGPORT (if it’s set). I have a .pgpass, but it’s empty so I didn’t have to do anything special for that. If you have a non-empty .pgpass, you might copy it aside before running psql if you want to try this test. Don’t forget to put it back when you’re done.

On my work machine, I had two versions of PostgreSQL running: 8.4 and 8.3. 8.3 was listening on 5432 and 8.4 was listening on 5433. psql was configured to go to port 5432 by default (and therefore PostgreSQL 8.3).