zero (o) return code on failure of pg_dump

I run a pg-dump in one of my scripts and want to send an e-mail on
failure (i.e. non-zero return code). This particular dump ran out of
disk space and failed. However, the return code is zero! Whether the
pg_dump succeeds or fails, zero is always returned. What is the best way
to check for the successful completion of the pg_dump?

I am running PostgreSQL 7.3 and Redhat Linux 6.2.

Thanks.

Regards,
Derek Main.