CHKPOINT=$(find $ARCHIVEDIR -type f -mtime +30 -name '00*' -printf '%f\n' | sort -r | head -1)/usr/pgsql-${PG_VERSION}/bin/pg_archivecleanup $ARCHIVEDIR $CHKPOINT
While I'm a bit suspect of this entire script/approach I believe the problem plaguing you at the moment is that your find command is not finding any files and thus your attempt to execute pg_archivecleanup only occurs with a single argument - which is an error.
For something this important I would advise considerably more debugging output and explicit error handling. Don't rely on set -e
On a related note - I don't understand why you'd use the "exec" command here...
David J.
