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 pending (If one of the signals in set is already
23 pending for the calling thread, sigwaitinfo() will return immediately.)
24 sigwaitinfo() removes the signal from the set of pending signals and
26 returns the signal number as its function result. If the info argument
27 is not NULL, then the buffer that it points to is used to return a
28 structure of type siginfo_t (see sigaction(2)) containing information
29 about the signal.
30 If multiple signals in set are pending for the caller, the signal that
32 is retrieved by sigwaitinfo() is determined according to the usual
33 ordering rules; see signal(7) for further details.
34 sigtimedwait() operates in exactly the same way as sigwaitinfo() except
36 that it has an additional argument, timeout, which specifies a minimum
37 interval for which the thread is suspended waiting for a signal. (This
38 interval will be rounded up to the system clock granularity, and kernel
39 scheduling delays mean that the interval may overrun by a small
40 amount.) This argument is of the following type:
41 struct timespec {
43 long tv_sec; /* seconds */
44 long tv_nsec; /* nanoseconds */
45 }
46 If both fields of this structure are specified as 0, a poll is per‐
48 formed: sigtimedwait() returns immediately, either with information
49 about a signal that was pending for the caller, or with an error if
50 none of the signals in set was pending.
51
53 On success, both sigwaitinfo() and sigtimedwait() return a signal num‐
54 ber (i.e., a value greater than zero). On failure both calls return
55 -1, with errno set to indicate the error.
56
58 EAGAIN No signal in set was became pending within the timeout period
59 specified to sigtimedwait().
60 EINTR The wait was interrupted by a signal handler; see signal(7).
62 (This handler was for a signal other than one of those in set.)
63 EINVAL timeout was invalid.
65
67 POSIX.1-2001.
68
70 In normal usage, the calling program blocks the signals in set via a
71 prior call to sigprocmask(2) (so that the default disposition for these
72 signals does not occur if they become pending between successive calls
73 to sigwaitinfo() or sigtimedwait()) and does not establish handlers for
74 these signals. In a multithreaded program, the signal should be
75 blocked in all threads, in order to prevent the signal being treated
76 according to its default disposition in a thread other than the one
77 calling sigwaitinfo() or sigtimedwait()).
78 The set of signals that is pending for a given thread is the union of
80 the set of signals that is pending specifically for that thread and the
81 set of signals that is pending for the process as a whole (see sig‐
82 nal(7)).
83 Attempts to wait for SIGKILL and SIGSTOP are silently ignored.
85 If multiple threads of a process are blocked waiting for the same sig‐
87 nal(s) in sigwaitinfo() or sigtimedwait(), then exactly one of the
88 threads will actually receive the signal if it becomes pending for the
89 process as a whole; which of the threads receives the signal is inde‐
90 terminate.
91 POSIX leaves the meaning of a NULL value for the timeout argument of
93 sigtimedwait() unspecified, permitting the possibility that this has
94 the same meaning as a call to sigwaitinfo(), and indeed this is what is
95 done on Linux.
96 On Linux, sigwaitinfo() is a library function implemented on top of
98 sigtimedwait().
99
101 kill(2), sigaction(2), signal(2), signalfd(2), sigpending(2), sigproc‐
102 mask(2), sigqueue(3), sigsetops(3), sigwait(3), signal(7), time(7)
103
105 This page is part of release 3.53 of the Linux man-pages project. A
106 description of the project, and information about reporting bugs, can
107 be found at http://www.kernel.org/doc/man-pages/.
108Linux 2012-07-21 SIGWAITINFO(2)