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Name

sigprocmask - change and/or examine caller’s signal mask

Synopsis

#include <signal.h>

int sigprocmask(int how, const sigset_t *set, sigset_t *oset);

MT-Level

Async-Signal-Safe

Description

The sigprocmask() function is used to examine and/or change the caller’s signal mask. If the value is SIG_BLOCK, the set pointed to by the argument set is added to the current signal mask. If the value is SIG_UNBLOCK, the set pointed by the argument set is removed from the current signal mask. If the value is SIG_SETMASK, the current signal mask is replaced by the set pointed to by the argument set. If the argument oset is not NULL, the previous mask is stored in the space pointed to by oset. If the value of the argument set 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 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 those signals that cannot be ignored (see sigaction(2) ); this restriction is silently imposed by the system.

If sigprocmask() fails, the caller’s signal mask is not changed.

Return Values

On success, sigprocmask() returns zero. On failure, it returns -1 and sets errno to indicate the error.

Errors

sigprocmask() fails if any of the following is true:

EFAULT
set or oset points to an illegal address.
EINVAL
The value of the how argument is not equal to one of the defined values.

See Also

sigaction(2) , signal(3C) , sigsetops(3C) , signal(5)

Notes

The language in the main body above should indicate that in a multi-threaded program, the call to sigpromask() impacts only the calling thread’s signal mask. Hence, it is identical to a call to thr_sigsetmask(3t) , in a multi-threaded program.

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