[net.bugs.4bsd] sh -c 'trap "" 10; date' vs. sh -c 'trap "" 11; date' on 4.?bsd

gwyn@brl-tgr.ARPA (Doug Gwyn <gwyn>) (09/14/84)

Yes, you cannot catch trap 11 in the Bourne shell since it is needed
internally for memory allocation purposes.  Newer shells give the
following message on your example:
	sh: bad trap: cannot trap 11