pg_command_launcher is a PostgreSQL extension which enables us to make PostgreSQL server execute the specified shell command at various timings.

$ make USE_PGXS=1 PG_CONFIG=/opt/pgsql-X.Y.Z/bin/pg_config
$ make USE_PGXS=1 PG_CONFIG=/opt/pgsql-X.Y.Z/bin/pg_config install
$ vi $PGDATA/postgresql.conf
shared_preload_libraries = 'pg_command_launcher'
pg_command_launcher.command_at_startup = 'echo TEST'

• pg_command_launcher.command_at_startup
  The shell command that will be executed at server startup.

• pg_command_launcher.command_at_shutdown
  The shell command that will be executed at server shutdown.