int
sigprocmask(
int how
, const sigset_t * restrict set
, sigset_t * restrict oset
)
)
function examines and/or changes the current signal mask (those signals
that are blocked from delivery).
Signals are blocked if they are members of the current signal mask set.
If
set
is not null, the action of
sigprocmask()
depends on the value of the parameter
how
.
The signal mask is changed as a function of the specified
set
and the current mask.
The function is specified by
how
using one of the following values:
SIG_BLOCK
set
.
SIG_UNBLOCK
set
.
SIG_SETMASK
set
.
If
oset
is not null, it is set to
the previous value of the signal mask.
When
set
is null,
the value of
how
is insignificant and the mask remains unset
providing a way to examine the signal mask without modification.
The system
quietly disallows
SIGKILL
or
SIGSTOP
to be blocked.
)
call will fail and the signal mask will be unchanged if one
of the following occurs:
EINVAL
]
how
has a value other than those listed here.
)
function conforms to
ISO/IEC 9945-1:1990 (``POSIX.1'') .