NAME

sigtimedwait, sigwaitinfo, sigwait — wait for queued signals

LIBRARY

Standard C Library (libc, -lc)

SYNOPSIS

#include <signal.h>

int
sigtimedwait(const sigset_t * restrict set, siginfo_t * restrict info, const struct timespec * restrict timeout);

int
sigwaitinfo(const sigset_t * restrict set, siginfo_t * restrict info);

int
sigwait(const sigset_t * restrict set, int * restrict sig);

DESCRIPTION

sigwaitinfo() and sigwait() return the first pending signal from the set specified by set. Should multiple signals from set be pending, the lowest numbered one is returned. The selection order between realtime and non-realtime signals is unspecified. If there is no signal from set pending at the time of the call, the calling thread is suspended until one of the specified signals is generated.

sigtimedwait() is exactly equal to sigwaitinfo(), except timeout specifies the maximum time interval for which the calling thread will be suspended. If timeout is zero (tv_sec == tv_nsec == 0), sigtimedwait() only checks the currently pending signals and returns immediately. If NULL is used for timeout, sigtimedwait() behaves exactly like sigwaitinfo() in all regards.

If several threads are waiting for a given signal, exactly one of them returns from the signal wait when the signal is generated.

Behaviour of these functions is unspecified if any of the signals in set are unblocked at the time these functions are called.

RETURN VALUES

Upon successful completion of sigtimedwait() or sigwaitinfo() info is updated with signal information, and the function returns the signal number. Otherwise, -1 is returned and the global variable errno indicates the error. Upon successful completion of sigwait() sig is updated with the signal number, and the function returns 0. Otherwise, a non-zero error code is returned.

ERRORS

sigwaitinfo() and sigwait() always succeed.

sigtimedwait() will fail and the info pointer will remain unchanged if:

[EAGAIN]

No signal specified in set was generated in the specified timeout.

sigtimedwait() may also fail if:

[EINVAL]

The specified timeout was invalid.

This error is only checked if no signal from set is pending and it would be necessary to wait.

SEE ALSO

sigaction(2), sigprocmask(2), signal(7)

STANDARDS

The functions sigtimedwait(), sigwaitinfo(), and sigwait() conform to IEEE Std 1003.1-2001 (“POSIX.1”).

HISTORY

The sigtimedwait(), sigwaitinfo(), and sigwait() functions appeared in NetBSD 2.0.