sigtimedwait , sigwaitinfo
- wait for queued signals (REALTIME)
LIBRARY
Lb libc
SYNOPSIS
#include <signal.h> int
Fo sigtimedwait
Fa const sigset_t *restrict set siginfo_t *restrict info
Fa const struct timespec *restrict timeout
Fc Ft int
sigwaitinfo (const sigset_t * restrict set siginfo_t * restrict info);
DESCRIPTION
The
sigtimedwait ();
system call is equivalent to
sigwaitinfo ();
except that if none of the signals specified by
Fa set
are pending,
sigtimedwait ();
waits for the time interval specified in the
Vt timespec
structure referenced by
Fa timeout .
If the
Vt timespec
structure pointed to by
Fa timeout
is zero-valued and if none of the signals specified by
Fa set
are pending, then
sigtimedwait ();
returns immediately with an error.
If
Fa timeout
is the
NULL
pointer, the behavior is unspecified.
CLOCK_MONOTONIC
clock is used to measure the time interval specified by the
Fa timeout
argument.
The
sigwaitinfo ();
system call selects the pending signal from the set specified by
Fa set .
Should any of multiple pending signals in the range
SIGRTMIN
to
SIGRTMAX
be selected, it shall be the lowest numbered one.
The
selection order between realtime and non-realtime signals, or
between multiple pending non-realtime signals, is unspecified.
If no signal in
Fa set
is pending at the time of the call, the calling thread
is suspended until one or more signals in
Fa set
become pending or until it is interrupted by an unblocked, caught signal.
The
sigwaitinfo ();
system call is equivalent to the
sigwait ();
system call if the
Fa info
argument is
NULL
If the
Fa info
argument is
non- NULL
the
sigwaitinfo ();
function is equivalent to
sigwait (,);
except that the selected signal number shall be stored in the
si_signo
member, and the cause of the signal shall be stored in the
si_code
member.
If any value is queued to the selected signal, the first such queued
value is dequeued and, if the info argument is
non- NULL
the value is stored in the
si_value
member of
Fa info .
The system resource used to queue the signal
is released and returned to the system for other use.
If no value is queued,
the content of the
si_value
member is zero-valued.
If no further signals are
queued for the selected signal, the pending indication for that signal
is reset.
RETURN VALUES
Upon successful completion (that is, one of the signals specified by
Fa set
is pending or is generated)
sigwaitinfo ();
and
sigtimedwait ();
return the selected signal number.
Otherwise, the functions return a value of -1
and set the global variable
errno
to indicate the error.
ERRORS
The
sigtimedwait ();
system call
will fail if:
Bq Er EAGAIN
No signal specified by set was generated within the specified timeout period.
The
sigtimedwait ();
and
sigwaitinfo ();
system calls fail if:
Bq Er EINTR
The wait was interrupted by an unblocked, caught signal.
Bq Er EFAULT
Any arguments point outside the allocated address space or there is a
memory protection fault.
The
sigtimedwait ();
system call may also fail if:
Bq Er EINVAL
The
Fa timeout
argument specified a
tv_nsec
value less than zero or greater than or equal
to 1000 million.
Kernel only checks for this error if no signal is pending in set and it
is necessary to wait.
