February 10, 2003 SIGTIMEDWAIT 2

### NAME

sigtimedwait, sigwaitinfo, sigwait - wait for queued signals

### LIBRARY

Standard C Library (libc, -lc)

### SYNOPSIS

```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 ```info` is updated with signal information, and the function returns 0. Otherwise, -1 is returned and the global variable errno indicates the error.

### 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 NetBSD2.0.

### AUTHORS

The initial NetBSD implementation of the signal wait functions was written by Jaromir Dolecek
<jdolecek@NetBSD.org>.