This section describes alternative signal handling functions derived
from BSD Unix. These facilities were an advance, in their time; today,
they are mostly obsolete, and supported mainly for compatibility with
There are many similarities between the BSD and POSIX signal handling
facilities, because the POSIX facilities were inspired by the BSD
facilities. Besides having different names for all the functions to
avoid conflicts, the main differences between the two are:
BSD Unix represents signal masks as an int bit mask, rather than
as a sigset_t object.
The BSD facilities use a different default for whether an interrupted
primitive should fail or resume. The POSIX facilities make system
calls fail unless you specify that they should resume. With the BSD
facility, the default is to make system calls resume unless you say they
should fail. See Interrupted Primitives.