SIGEMPTYSET(3P)

💅 SIGEMPTYSET(3P) — the POSIX Programmer's Manual page, but make it cute

okay bestie, so this one lives in the POSIX Programmer's Manual, and here's the tea you gotta know before we even start:

PROLOG: 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.

like, no cap, read that twice. 🫶

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✨ NAME ✨

sigemptyset — initialize and empty a signal set

literally it makes a signal set and it's empty. the name ate, honestly. 💖

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🌸 SYNOPSIS 🌸

#include <signal.h>

int sigemptyset(sigset_t *set);

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🦋 DESCRIPTION 🦋

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

so like… every signal? excluded. gone. not invited to the party. 🙈

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💀 RETURN VALUE 💀

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

zero means slay, minus one means something went wrong and errno is gonna tell you the whole story.

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🎀 ERRORS 🎀

No errors are defined.

that's it. that's the section. no errors. iconic behaviour honestly. ✨

The following sections are informative.

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🍓 EXAMPLES 🍓

None.

(not one single example. they left us on read. 😭)

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💜 APPLICATION USAGE 💜

None.

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🧚 RATIONALE 🧚

okay so the reasoning behind all this, sit down bestie:

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.

🚨 read this part twice, fr fr: you must call either sigemptyset() or sigfillset() before you use the signal set for anything else — even if all you're doing is read-only stuff, like passing it to sigpending(). and no, it's not for dynamic allocation. periodt.

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.

ngl the whole "invalid vs unsupported signals" saga is giving academic drama and i'm kind of obsessed. 📚✨

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🌈 FUTURE DIRECTIONS 🌈

None.

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👑 SEE ALSO 👑

• Section 2.4, Signal Concepts
• pthread_sigmask()
• sigaction()
• sigaddset()
• sigdelset()
• sigfillset()
• sigismember()
• sigpending()
• sigsuspend()

The Base Definitions volume of POSIX.1‐2017, <signal.h>

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📜 COPYRIGHT 📜

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 .

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and that's the whole page, bestie 💖 this one's signed off by IEEE/The Open Group, dated 2017, tagged SIGEMPTYSET(3P) — so go forth, empty that signal set, and stay hydrated 🫶🎀✨