SIGPROCMASK(2) System Calls SIGPROCMASK(2)
NAME
sigprocmask - change or examine caller's signal mask
SYNOPSIS
#include <signal.h>
int sigprocmask(
int how,
const sigset_t *restrict set,
sigset_t *restrict oset);
DESCRIPTION
The
sigprocmask() function is used to examine and/or change the
caller's signal mask. If the value of the
how argument is
SIG_BLOCK,
the set pointed to by the
set argument is added to the current signal
mask. If the value of the
how argument is
SIG_UNBLOCK, the set
pointed by the
set argument is removed from the current signal mask.
If the value of the
how argument is
SIG_SETMASK, the current signal
mask is replaced by the set pointed to by the
set argument. If the
oset argument is not
NULL, the previous mask is stored in the space
pointed to by
oset. If the value of the
set argument is
NULL, the
value
how is not significant and the caller's signal mask is
unchanged; thus, the call can be used to inquire about currently
blocked signals. If the
set or
oset argument points to an invalid
address, the behavior is undefined and
errno may be set to
EFAULT.
If there are any pending unblocked signals after the call to
sigprocmask(), at least one of those signals will be delivered before
the call to
sigprocmask() returns.
It is not possible to block signals that cannot be caught or ignored
(see
sigaction(2)). It is also not possible to block or unblock
SIGCANCEL, as SIGCANCEL is reserved for the implementation of POSIX
thread cancellation (see
pthread_cancel(3C) and
cancellation(7)).
This restriction is silently enforced by the standard C library.
If
sigprocmask() fails, the caller's signal mask is not changed.
RETURN VALUES
Upon successful completion,
0 is returned. Otherwise,
-1 is returned
and
errno is set to indicate the error.
ERRORS
The
sigprocmask() function will fail if:
EINVAL The value of the
how argument is not equal to one of the
defined values.
The
sigprocmask() function may fail if:
EFAULT The
set or
oset argument points to an illegal address.
ATTRIBUTES
See
attributes(7) for descriptions of the following attributes:
+--------------------+-------------------+
| ATTRIBUTE TYPE | ATTRIBUTE VALUE |
+--------------------+-------------------+
|Interface Stability | Standard |
+--------------------+-------------------+
|MT-Level | Async-Signal-Safe |
+--------------------+-------------------+
SEE ALSO
sigaction(2),
pthread_cancel(3C),
pthread_sigmask(3C),
signal(3C),
sigsetops(3C),
signal.h(3HEAD),
attributes(7),
cancellation(7)NOTES
The call to
sigprocmask() affects only the calling thread's signal
mask. It is identical to a call to
pthread_sigmask(3C).
Signals that are generated synchronously should not be masked. If
such a signal is blocked and delivered, the receiving process is
killed.
November 24, 2014 SIGPROCMASK(2)
