1SIGWAITINFO(2) Linux Programmer's Manual SIGWAITINFO(2)
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6 sigwaitinfo, sigtimedwait - synchronously wait for queued signals
7
9 #include <signal.h>
10 int sigwaitinfo(const sigset_t *set, siginfo_t *info);
12 int sigtimedwait(const sigset_t *set, siginfo_t *info,
14 const struct timespec *timeout);
15 Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
17 sigwaitinfo(), sigtimedwait(): _POSIX_C_SOURCE >= 199309L
19
21 sigwaitinfo() suspends execution of the calling thread until one of the
22 signals in set is delivered. (If one of the signals in set is already
23 pending for the calling thread, sigwaitinfo() will return immediately
24 with information about that signal.)
25 sigwaitinfo() removes the delivered signal from the set of pending sig‐
27 nals and returns the signal number as its function result. If the info
28 argument is not NULL, then it returns a structure of type siginfo_t
29 (see sigaction(2)) containing information about the signal.
30 Signals returned via sigwaitinfo() are delivered in the usual order;
32 see signal(7) for further details.
33 sigtimedwait() operates in exactly the same way as sigwaitinfo() except
35 that it has an additional argument, timeout, which enables an upper
36 bound to be placed on the time for which the thread is suspended. This
37 argument is of the following type:
38 struct timespec {
40 long tv_sec; /* seconds */
41 long tv_nsec; /* nanoseconds */
42 }
43 If both fields of this structure are specified as 0, a poll is per‐
45 formed: sigtimedwait() returns immediately, either with information
46 about a signal that was pending for the caller, or with an error if
47 none of the signals in set was pending.
48
50 On success, both sigwaitinfo() and sigtimedwait() return a signal num‐
51 ber (i.e., a value greater than zero). On failure both calls return
52 -1, with errno set to indicate the error.
53
55 EAGAIN No signal in set was delivered within the timeout period speci‐
56 fied to sigtimedwait().
57 EINTR The wait was interrupted by a signal handler; see signal(7).
59 (This handler was for a signal other than one of those in set.)
60 EINVAL timeout was invalid.
62
64 POSIX.1-2001.
65
67 In normal usage, the calling program blocks the signals in set via a
68 prior call to sigprocmask(2) (so that the default disposition for these
69 signals does not occur if they are delivered between successive calls
70 to sigwaitinfo() or sigtimedwait()) and does not establish handlers for
71 these signals. In a multithreaded program, the signal should be
72 blocked in all threads to prevent the signal being delivered to a
73 thread other than the one calling sigwaitinfo() or sigtimedwait()).
74 The set of signals that is pending for a given thread is the union of
76 the set of signals that is pending specifically for that thread and the
77 set of signals that is pending for the process as a whole (see sig‐
78 nal(7)).
79 If multiple threads of a process are blocked waiting for the same sig‐
81 nal(s) in sigwaitinfo() or sigtimedwait(), then exactly one of the
82 threads will actually receive the signal if it is delivered to the
83 process as a whole; which of the threads receives the signal is inde‐
84 terminate.
85 POSIX leaves the meaning of a NULL value for the timeout argument of
87 sigtimedwait() unspecified, permitting the possibility that this has
88 the same meaning as a call to sigwaitinfo(), and indeed this is what is
89 done on Linux.
90 On Linux, sigwaitinfo() is a library function implemented on top of
92 sigtimedwait().
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95 kill(2), sigaction(2), signal(2), signalfd(2), sigpending(2), sigproc‐
96 mask(2), sigqueue(2), sigsetops(3), sigwait(3), signal(7), time(7)
97
99 This page is part of release 3.25 of the Linux man-pages project. A
100 description of the project, and information about reporting bugs, can
101 be found at http://www.kernel.org/doc/man-pages/.
102Linux 2008-10-04 SIGWAITINFO(2)