SIGPROCMASK(2) Linux Programmers Manual SIGPROCMASK(2)
sigprocmask - examine and change blocked signals
int sigprocmask(int how, const sigset_t *set, sigset_t *oldset);
sigprocmask() is used to change the signal mask, the set of currently
blocked signals. The behavior of the call is dependent on the value of
how, as follows.
The set of blocked signals is the union of the current set and
the set argument.
The signals in set are removed from the current set of blocked
signals. It is permissible to attempt to unblock a signal which
is not blocked.
The set of blocked signals is set to the argument set.
If oldset is non-null, the previous value of the signal mask is stored
If set is NULL, then the signal mask is unchanged (i.e., how is
ignored), but the current value of the signal mask is nevertheless
returned in oldset (it is not NULL).
The use of sigprocmask() is unspecified in a multithreaded process; see
sigprocmask() returns 0 on success and -1 on error.
EINVAL The value specified in how was invalid.
It is not possible to block SIGKILL or SIGSTOP. Attempts to do so are
If SIGBUS, SIGFPE, SIGILL, or SIGSEGV are generated while they are
blocked, the result is undefined, unless the signal was generated by
the kill(2), sigqueue(2), or raise(3).
See sigsetops(3) for details on manipulating signal sets.
kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigqueue(2),
sigsuspend(2), pthread_sigmask(3), sigsetops(3), signal(7)
This page is part of release 3.05 of the Linux man-pages project. A
description of the project, and information about reporting bugs, can
be found at http://www.kernel.org/doc/man-pages/.
Linux 2005-09-15 SIGPROCMASK(2)