sigprocmask - examine and change blocked signals

#include <signal.h> 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 behaviour of the call is dependent on the value of how, as follows.

SIG_BLOCK

The set of blocked signals is the union of the current set and the set argument.

SIG_UNBLOCK

The signals in set are removed from the current set of blocked signals. It is legal to attempt to unblock a signal which is not blocked.

SIG_SETMASK

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 in oldset.

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 it is not NULL).

The use of sigprocmask() is unspecified in a multithreaded process; see pthread_sigmask(3).

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 silently ignored.

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.

POSIX.1-2001.

kill(2), pause(2), sigaction(2), signal(2), sigpending(2), sigprocmask(2), sigqueue(2), sigsuspend(2), pthread_sigmask(3), sigsetops(3), signal(7)