kör locate initdb det bör ge dig listan att välja. smth som:
MacBook-Air:~ vao$ locate initdb
/usr/local/Cellar/postgresql/9.5.3/bin/initdb
/usr/local/Cellar/postgresql/9.5.3/share/doc/postgresql/html/app-initdb.html
/usr/local/Cellar/postgresql/9.5.3/share/man/man1/initdb.1
/usr/local/Cellar/postgresql/9.6.1/bin/initdb
/usr/local/Cellar/postgresql/9.6.1/share/doc/postgresql/html/app-initdb.html
/usr/local/Cellar/postgresql/9.6.1/share/man/man1/initdb.1
/usr/local/bin/initdb
/usr/local/share/man/man1/initdb.1
Så i mitt fall vill jag köra
/usr/local/Cellar/postgresql/9.6.1/bin/initdb
Om du inte har mlocate installerat, antingen installera det eller använd
sudo find / -name initdb