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.