1SIGEMPTYSET(P) POSIX Programmer's Manual SIGEMPTYSET(P)
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6 sigemptyset - initialize and empty a signal set
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9 #include <signal.h>
10 int sigemptyset(sigset_t *set);
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15 The sigemptyset() function initializes the signal set pointed to by
16 set, such that all signals defined in IEEE Std 1003.1-2001 are
17 excluded.
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20 Upon successful completion, sigemptyset() shall return 0; otherwise, it
21 shall return -1 and set errno to indicate the error.
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24 No errors are defined.
25 The following sections are informative.
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29 None.
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32 None.
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35 The implementation of the sigemptyset() (or sigfillset()) function
36 could quite trivially clear (or set) all the bits in the signal set.
37 Alternatively, it would be reasonable to initialize part of the struc‐
38 ture, such as a version field, to permit binary-compatibility between
39 releases where the size of the set varies. For such reasons, either
40 sigemptyset() or sigfillset() must be called prior to any other use of
41 the signal set, even if such use is read-only (for example, as an argu‐
42 ment to sigpending()). This function is not intended for dynamic allo‐
43 cation.
44 The sigfillset() and sigemptyset() functions require that the resulting
46 signal set include (or exclude) all the signals defined in this volume
47 of IEEE Std 1003.1-2001. Although it is outside the scope of this vol‐
48 ume of IEEE Std 1003.1-2001 to place this requirement on signals that
49 are implemented as extensions, it is recommended that implementation-
50 defined signals also be affected by these functions. However, there may
51 be a good reason for a particular signal not to be affected. For exam‐
52 ple, blocking or ignoring an implementation-defined signal may have
53 undesirable side effects, whereas the default action for that signal is
54 harmless. In such a case, it would be preferable for such a signal to
55 be excluded from the signal set returned by sigfillset().
56 In early proposals there was no distinction between invalid and unsup‐
58 ported signals (the names of optional signals that were not supported
59 by an implementation were not defined by that implementation). The
60 [EINVAL] error was thus specified as a required error for invalid sig‐
61 nals. With that distinction, it is not necessary to require implementa‐
62 tions of these functions to determine whether an optional signal is
63 actually supported, as that could have a significant performance impact
64 for little value. The error could have been required for invalid sig‐
65 nals and optional for unsupported signals, but this seemed unnecessar‐
66 ily complex. Thus, the error is optional in both cases.
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69 None.
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72 Signal Concepts , sigaction() , sigaddset() , sigdelset() , sig‐
73 fillset() , sigismember() , sigpending() , sigprocmask() , sigsuspend()
74 , the Base Definitions volume of IEEE Std 1003.1-2001, <signal.h>
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77 Portions of this text are reprinted and reproduced in electronic form
78 from IEEE Std 1003.1, 2003 Edition, Standard for Information Technology
79 -- Portable Operating System Interface (POSIX), The Open Group Base
80 Specifications Issue 6, Copyright (C) 2001-2003 by the Institute of
81 Electrical and Electronics Engineers, Inc and The Open Group. In the
82 event of any discrepancy between this version and the original IEEE and
83 The Open Group Standard, the original IEEE and The Open Group Standard
84 is the referee document. The original Standard can be obtained online
85 at http://www.opengroup.org/unix/online.html .
86IEEE/The Open Group 2003 SIGEMPTYSET(P)