Location of postgresql database on OS X?

In my case (not homebrew) the data location is found in this file /Library/LaunchDaemons/com.edb.launchd.postgresql-9.3.plist

   <array>
            <string>/Users/me/bin/postgres/bin/postmaster</string>
            <string>-D/Users/me/data/postgres</string>
   </array>

initdb just sets up the directory structure and such that is needed to create new databases. To create a database, use createdb:

SYNOPSIS
createdb [ option... ] [ dbname ] [ description ]

DESCRIPTION
createdb creates a new PostgreSQL database.

Normally, the database user who executes this command becomes the owner of the new database. However a different owner can be specified via the -O option, if the executing user has appropriate privileges.

createdb is a wrapper around the SQL command CREATE DATABASE [create_database(7)]. There is no effective difference between creating databases via this utility and via other methods for accessing the server.

initdb is sort of like creating a new file system on a hard disk: first you create the file system (initdb), then you create a files and directories (createdb).

The actual database files will be under /usr/local/var/postgres after you create the database. So, just create a database and then see what's new or changed under /usr/local/var/postgres. There isn't a single "dbname.db" file or anything like that, each database is a collection of files with names that are only meaningful to the database server.

Run the following query:

SHOW DATA_DIRECTORY;