# psql -U postgres template1 -c "select pg_backup_stop(true)" ERROR: backup is not in progress HINT: Did you call pg_backup_start()?
This is postgresql 15.6 running on RH 7.
This is not just amusing, it is breaking my backup script after update from 11 to 15 (and change from pg_{start,stop}_backup to pg_backup_{start_stop})
Yep, nowadays you must keep the transaction where you issued backup start open until you issue backup end. Using -c isn't going to cut it.