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)