$ brew install postgres
==> Downloading https://homebrew.bintray.com/bottles/postgresql-9.6.5.sierra.bottle.tar.gz
######################################################################## 100.0%
==> Pouring postgresql-9.6.5.sierra.bottle.tar.gz
==> /usr/local/Cellar/postgresql/9.6.5/bin/initdb /usr/local/var/postgres
==> Caveats
<snip>
To have launchd start postgresql now and restart at login:
brew services start postgresql
Or, if you don't want/need a background service you can just run:
pg_ctl -D /usr/local/var/postgres start
==> Summary
🍺 /usr/local/Cellar/postgresql/9.6.5: 3,269 files, 36.7MB