SIGWAITINFO(2) Linux Programmers Manual SIGWAITINFO(2)
NAME
sigwaitinfo, sigtimedwait - synchronously wait for queued signals
SYNOPSIS
#include
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 processs
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 per
formed: 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 num
ber (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 speci
fied 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 sig
nal(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), sigproc
mask(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/.
Linux 2008-06-02 SIGWAITINFO(2)
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