An install of PostgreSQL comes with a number of utilities including the
pg_isready command. This command can be used to check if the local PostgreSQL
server is up, running, and ready to receive connections.
If the server has not yet been started, running the command will result in a
no response response.
$ pg_isready
localhost:5432 - no responseIn this case, the pg_ctl command can be used to start the server.
$ pg_ctl -D $HOME/.asdf/installs/postgres/12.3/data start
waiting for server to start....
...
done
server startedIt tells us that the server is started and we can confirm that by again running
pg_isready.
$ pg_isready
localhost:5432 - accepting connectionsThis command is most useful as part of a script, such as in a CI environment.
In that case, you may not want it writing to stdout, you just want to use the
command's exit code. For that, you can tack on the --quiet flag.
$ pg_isready --quiet