SIGWAITINFO(2) Linux Programmer's Manual SIGWAITINFO(2)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);
DESCRIPTIONsigwaitinfo() 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 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. (This handler was
for a signal other than one of those in set.)
EINVAL timeout was invalid.
NOTES
In normal usage, the calling program blocks the signals in set via a
prior call to sigprocmask() (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()).
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.
CONFORMING TO
POSIX.1-2001
SEE ALSOkill(2), sigaction(2), signal(2), sigpending(2), sigprocmask(2),
sigqueue(2), sigsetops(3), signal(7)Linux 2.4.18 2002-06-07 SIGWAITINFO(2)