1SIGEMPTYSET(3P)            POSIX Programmer's Manual           SIGEMPTYSET(3P)
2
3
4

PROLOG

6       This  manual  page is part of the POSIX Programmer's Manual.  The Linux
7       implementation of this interface may differ (consult the  corresponding
8       Linux  manual page for details of Linux behavior), or the interface may
9       not be implemented on Linux.
10

NAME

12       sigemptyset — initialize and empty a signal set
13

SYNOPSIS

15       #include <signal.h>
16
17       int sigemptyset(sigset_t *set);
18

DESCRIPTION

20       The sigemptyset() function initializes the signal  set  pointed  to  by
21       set, such that all signals defined in POSIX.1‐2008 are excluded.
22

RETURN VALUE

24       Upon successful completion, sigemptyset() shall return 0; otherwise, it
25       shall return -1 and set errno to indicate the error.
26

ERRORS

28       No errors are defined.
29
30       The following sections are informative.
31

EXAMPLES

33       None.
34

APPLICATION USAGE

36       None.
37

RATIONALE

39       The implementation of  the  sigemptyset()  (or  sigfillset())  function
40       could  quite  trivially  clear (or set) all the bits in the signal set.
41       Alternatively, it would be reasonable to initialize part of the  struc‐
42       ture,  such  as a version field, to permit binary-compatibility between
43       releases where the size of the set varies.  For  such  reasons,  either
44       sigemptyset()  or sigfillset() must be called prior to any other use of
45       the signal set, even if such use is read-only (for example, as an argu‐
46       ment to sigpending()).  This function is not intended for dynamic allo‐
47       cation.
48
49       The sigfillset() and sigemptyset() functions require that the resulting
50       signal  set include (or exclude) all the signals defined in this volume
51       of POSIX.1‐2017. Although it is outside the scope  of  this  volume  of
52       POSIX.1‐2017  to place this requirement on signals that are implemented
53       as extensions, it is recommended  that  implementation-defined  signals
54       also  be affected by these functions. However, there may be a good rea‐
55       son for a particular signal not to be affected. For  example,  blocking
56       or ignoring an implementation-defined signal may have undesirable side-
57       effects, whereas the default action for that  signal  is  harmless.  In
58       such  a  case,  it would be preferable for such a signal to be excluded
59       from the signal set returned by sigfillset().
60
61       In early proposals there was no distinction between invalid and  unsup‐
62       ported  signals  (the names of optional signals that were not supported
63       by an implementation were not  defined  by  that  implementation).  The
64       [EINVAL]  error was thus specified as a required error for invalid sig‐
65       nals. With that distinction, it is not necessary to require implementa‐
66       tions  of  these  functions  to determine whether an optional signal is
67       actually supported, as that could have a significant performance impact
68       for  little  value. The error could have been required for invalid sig‐
69       nals and optional for unsupported signals, but this seemed  unnecessar‐
70       ily complex. Thus, the error is optional in both cases.
71

FUTURE DIRECTIONS

73       None.
74

SEE ALSO

76       Section 2.4, Signal Concepts, pthread_sigmask(), sigaction(),
77       sigaddset(), sigdelset(), sigfillset(), sigismember(), sigpending(),
78       sigsuspend()
79
80       The Base Definitions volume of POSIX.1‐2017, <signal.h>
81
83       Portions  of  this text are reprinted and reproduced in electronic form
84       from IEEE Std 1003.1-2017, Standard for Information Technology --  Por‐
85       table  Operating System Interface (POSIX), The Open Group Base Specifi‐
86       cations Issue 7, 2018 Edition, Copyright (C) 2018 by the  Institute  of
87       Electrical  and  Electronics Engineers, Inc and The Open Group.  In the
88       event of any discrepancy between this version and the original IEEE and
89       The  Open Group Standard, the original IEEE and The Open Group Standard
90       is the referee document. The original Standard can be  obtained  online
91       at http://www.opengroup.org/unix/online.html .
92
93       Any  typographical  or  formatting  errors that appear in this page are
94       most likely to have been introduced during the conversion of the source
95       files  to  man page format. To report such errors, see https://www.ker
96       nel.org/doc/man-pages/reporting_bugs.html .
97
98
99
100IEEE/The Open Group                  2017                      SIGEMPTYSET(3P)
Impressum