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SIGWAITINFO
Section: Linux Programmer's Manual (2)
Updated: 2008-06-02
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NAME
sigwaitinfo, sigtimedwait - synchronously wait for queued signals
SYNOPSIS
#include <signal.h>
int sigwaitinfo(const sigset_t *set, siginfo_t *info);
int sigtimedwait(const sigset_t *set, siginfo_t *info,
const struct timespec *timeout);
Feature Test Macro Requirements for glibc (see
feature_test_macros(7)):
sigwaitinfo(),
sigtimedwait():
_POSIX_C_SOURCE >= 199309L
DESCRIPTION
sigwaitinfo()
suspends execution of the calling process until one of the signals in
set
is delivered.
(If one of the signals in
set
is already pending for the calling process,
sigwaitinfo()
will return immediately with information about that signal.)
sigwaitinfo()
removes the delivered signal from the calling process's list of pending
signals and returns the signal number as its function result.
If the
info
argument is not NULL,
then it returns a structure of type
siginfo_t
(see
sigaction(2))
containing information about the signal.
Signals returned via
sigwaitinfo()
are delivered in the usual order; see
signal(7)
for further details.
sigtimedwait()
operates in exactly the same way as
sigwaitinfo()
except that it has an additional argument,
timeout,
which enables an upper bound to be placed on the time for which
the process is suspended.
This argument is of the following type:
struct timespec {
long tv_sec; /* seconds */
long tv_nsec; /* nanoseconds */
}
If both fields of this structure are specified as 0, a poll is performed:
sigtimedwait()
returns immediately, either with information about a signal that
was pending for the caller, or with an error
if none of the signals in
set
was pending.
RETURN VALUE
On success, both
sigwaitinfo()
and
sigtimedwait()
return a signal number (i.e., a value greater than zero).
On failure both calls return -1, with
errno
set to indicate the error.
ERRORS
- EAGAIN
-
No signal in
set
was delivered within the
timeout
period specified to
sigtimedwait().
- EINTR
-
The wait was interrupted by a signal handler; see
signal(7).
(This handler was for a signal other than one of those in
set.)
- EINVAL
-
timeout
was invalid.
CONFORMING TO
POSIX.1-2001.
NOTES
In normal usage, the calling program blocks the signals in
set
via a prior call to
sigprocmask(2)
(so that the default disposition for these signals does not occur if they
are delivered between successive calls to
sigwaitinfo()
or
sigtimedwait())
and does not establish handlers for these signals.
In a multithreaded program,
the signal should be blocked in all threads to prevent
the signal being delivered to a thread other than the one calling
sigwaitinfo()
or
sigtimedwait()).
If multiple threads of a process are blocked
waiting for the same signal(s) in
sigwaitinfo()
or
sigtimedwait(),
then exactly one of the threads will actually receive the
signal when it is generated;
which of the threads receives the signal is indeterminate.
POSIX leaves the meaning of a NULL value for the
timeout
argument of
sigtimedwait()
unspecified, permitting the possibility that this has the same meaning
as a call to
sigwaitinfo(),
and indeed this is what is done on Linux.
On Linux,
sigwaitinfo()
is a library function implemented on top of
sigtimedwait().
SEE ALSO
kill(2),
sigaction(2),
signal(2),
signalfd(2),
sigpending(2),
sigprocmask(2),
sigqueue(2),
sigsetops(3),
sigwait(3),
signal(7),
time(7)
COLOPHON
This page is part of release 3.05 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.
Index
- NAME
-
- SYNOPSIS
-
- DESCRIPTION
-
- RETURN VALUE
-
- ERRORS
-
- CONFORMING TO
-
- NOTES
-
- SEE ALSO
-
- COLOPHON
-
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