unix_domain_socket_dir

[apsheronets]

Looks like it's /var/run/postgresql for async and /tmp for everything else.

[richardhuxton]

The PostgreSQL source-code defaults to /tmp (see src/backend/utils/misc/postgresql.conf.sample) probably because of the large number of pllatforms it supports. However, both Debian and Red-Hat based linux distros use /var/run/postgresql for their packages. I suspect any other linux distros would too. I'm guessing people using homebrew or similar on a Mac might get "/tmp" - no idea about Windows.