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SIGWAITINFO(2)             Linux Programmer's Manual            SIGWAITINFO(2)

       sigwaitinfo, sigtimedwait - synchronously wait for queued signals

       #include <&lt;signal.h>&gt;

       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

       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  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

       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.

       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.

       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.


       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

       kill(2), sigaction(2), signal(2), signalfd(2), sigpending(2),  sigproc-
       mask(2), sigqueue(2), sigsetops(3), sigwait(3), signal(7), time(7)

       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)