The Single UNIX ® Specification, Version 2
Copyright © 1997 The Open Group


sigwaitinfo, sigtimedwait - wait for queued signals (REALTIME)


#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);


The function sigwaitinfo() selects the pending signal from the set specified by set. Should any of multiple pending signals in the range SIGRTMIN to SIGRTMAX be selected, it will 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 set is pending at the time of the call, the calling thread is suspended until one or more signals in set become pending or until it is interrupted by an unblocked, caught signal.

The function sigwaitinfo() behaves the same as the sigwait() function if the info argument is NULL. If the info argument is non-NULL, the sigwaitinfo() function behaves the same as sigwait,() except that the selected signal number is stored in the si_signo member, and the cause of the signal is 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 info. The system resource used to queue the signal will be released and made available to queue other signals. If no value is queued, the content of the si_value member is undefined. If no further signals are queued for the selected signal, the pending indication for that signal will be reset.

The function sigtimedwait() behaves the same as sigwaitinfo() except that if none of the signals specified by set are pending, sigtimedwait() waits for the time interval specified in the timespec structure referenced by timeout. If the timespec structure pointed to by timeout is zero-valued and if none of the signals specified by set are pending, then sigtimedwait() returns immediately with an error. If timeout is the NULL pointer, the behaviour is unspecified.


Upon successful completion (that is, one of the signals specified by set is pending or is generated) sigwaitinfo() and sigtimedwait() will return the selected signal number. Otherwise, the function returns a value of -1 and sets errno to indicate the error.


The sigwaitinfo() and sigtimedwait() functions will fail if:
The functions sigwaitinfo() and sigtimedwait() are not supported by this implementation.

The sigtimedwait() function will also fail if:

No signal specified by set was generated within the specified timeout period.

The sigwaitinfo() and sigtimedwait() functions may fail if:

The wait was interrupted by an unblocked, caught signal. It will be documented in system documentation whether this error will cause these functions to fail.

The sigtimedwait() function may also fail if:

The timeout argument specified a tv_nsec value less than zero or greater than or equal to 1000 million.

An implementation only checks for this error if no signal is pending in set and it is necessary to wait.








pause(), pthread_sigmask(), sigaction(), <signal.h>, sigpending(), sigsuspend(), sigwait(), <time.h>.


Derived from the POSIX Realtime Extension (1003.1b-1993/1003.1i-1995) and the POSIX Threads Extension (1003.1c-1995)

UNIX ® is a registered Trademark of The Open Group.
Copyright © 1997 The Open Group
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