SIGTIMEDWAIT(2) | System Calls Manual | SIGTIMEDWAIT(2)

# 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.

April 2, 2012 | NetBSD 9.4