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PROLOG | NAME | SYNOPSIS | DESCRIPTION | RETURN VALUE | ERRORS | EXAMPLES | APPLICATION USAGE | RATIONALE | FUTURE DIRECTIONS | SEE ALSO | COPYRIGHT |
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SIGEMPTYSET(3P) POSIX Programmer's Manual SIGEMPTYSET(3P)
This manual page is part of the POSIX Programmer's Manual. The
Linux implementation of this interface may differ (consult the
corresponding Linux manual page for details of Linux behavior), or
the interface may not be implemented on Linux.
sigemptyset — initialize and empty a signal set
#include <signal.h>
int sigemptyset(sigset_t *set);
The sigemptyset() function initializes the signal set pointed to
by set, such that all signals defined in POSIX.1‐2008 are
excluded.
Upon successful completion, sigemptyset() shall return 0;
otherwise, it shall return -1 and set errno to indicate the error.
No errors are defined.
The following sections are informative.
None.
None.
The implementation of the sigemptyset() (or sigfillset()) function
could quite trivially clear (or set) all the bits in the signal
set. Alternatively, it would be reasonable to initialize part of
the structure, such as a version field, to permit binary-
compatibility between releases where the size of the set varies.
For such reasons, either sigemptyset() or sigfillset() must be
called prior to any other use of the signal set, even if such use
is read-only (for example, as an argument to sigpending()). This
function is not intended for dynamic allocation.
The sigfillset() and sigemptyset() functions require that the
resulting signal set include (or exclude) all the signals defined
in this volume of POSIX.1‐2017. Although it is outside the scope
of this volume of POSIX.1‐2017 to place this requirement on
signals that are implemented as extensions, it is recommended that
implementation-defined signals also be affected by these
functions. However, there may be a good reason for a particular
signal not to be affected. For example, blocking or ignoring an
implementation-defined signal may have undesirable side-effects,
whereas the default action for that signal is harmless. In such a
case, it would be preferable for such a signal to be excluded from
the signal set returned by sigfillset().
In early proposals there was no distinction between invalid and
unsupported signals (the names of optional signals that were not
supported by an implementation were not defined by that
implementation). The [EINVAL] error was thus specified as a
required error for invalid signals. With that distinction, it is
not necessary to require implementations of these functions to
determine whether an optional signal is actually supported, as
that could have a significant performance impact for little value.
The error could have been required for invalid signals and
optional for unsupported signals, but this seemed unnecessarily
complex. Thus, the error is optional in both cases.
None.
Section 2.4, Signal Concepts, pthread_sigmask(3p), sigaction(3p),
sigaddset(3p), sigdelset(3p), sigfillset(3p), sigismember(3p),
sigpending(3p), sigsuspend(3p)
The Base Definitions volume of POSIX.1‐2017, signal.h(0p)
Portions of this text are reprinted and reproduced in electronic
form from IEEE Std 1003.1-2017, Standard for Information
Technology -- Portable Operating System Interface (POSIX), The
Open Group Base Specifications Issue 7, 2018 Edition, Copyright
(C) 2018 by the Institute of Electrical and Electronics Engineers,
Inc and The Open Group. In the event of any discrepancy between
this version and the original IEEE and The Open Group Standard,
the original IEEE and The Open Group Standard is the referee
document. The original Standard can be obtained online at
http://www.opengroup.org/unix/online.html .
Any typographical or formatting errors that appear in this page
are most likely to have been introduced during the conversion of
the source files to man page format. To report such errors, see
https://www.kernel.org/doc/man-pages/reporting_bugs.html .
IEEE/The Open Group 2017 SIGEMPTYSET(3P)
Pages that refer to this page: signal.h(0p), pthread_sigmask(3p), sigaction(3p), sigaddset(3p), sigdelset(3p), sigfillset(3p), sigismember(3p), sigpending(3p), sigsuspend(3p)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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