sigwaitinfo() - Unix, Linux System Call
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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);
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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 */
}
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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
Tag | Description |
EAGAIN |
No signal in
set was delivered within the
timeout period specified 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.
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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 ALSO
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