SEM_CLOSE(3POSIX)

📦 version 2017a, in debian bookworm, debian trixie, ubuntu jammy, ubuntu noble, ubuntu resolute, ubuntu stonking

💖 SEM_CLOSE(3POSIX) 💖

okay bestie, welcome to the POSIX Programmer's Manual ✨ (that's the manual name, mwah, we're being formal for exactly one second)

🌸 PROLOG 🌸

okay so real talk before we get into it — this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so like, go check the corresponding Linux manual page for the deets on Linux behavior, no cap), or the interface might not even be implemented on Linux at all. 💀 just so you know what you're walking into.

🎀 NAME 🎀

sem_close — close a named semaphore

✨ SYNOPSIS ✨

#include <semaphore.h>

int sem_close(sem_t *sem);

👑 DESCRIPTION 👑

so sem_close() is literally you telling the system "bestie i'm done with this named semaphore", where the semaphore in question is the one pointed at by sem. 💅

okay now the important bits, listen up:

  • if you call sem_close() on an unnamed semaphore (aka one that was created by sem_init()), the effects are undefined. not "probably fine". undefined. 🙈
  • sem_close() shall deallocate — that is, make available for reuse by a subsequent sem_open() by this process — any system resources that the system allocated for use by this process for this semaphore. ♻️
  • the effect of subsequent use of the semaphore indicated by sem by this process is undefined. so like... don't. 🚫
  • if any threads in the calling process are currently blocked on the semaphore, the behavior is undefined. 😭
  • if the semaphore has not been removed with a successful call to sem_unlink(), then sem_close() has no effect on the state of the semaphore. like, zero. none. the semaphore just keeps on vibing. 🦋
  • if sem_unlink() has been successfully invoked for name after the most recent call to sem_open() with O_CREAT for this semaphore, then when all processes that have opened the semaphore close it, the semaphore is no longer accessible. periodt. 👑

🌈 RETURN VALUE 🌈

  • upon successful completion, a value of zero shall be returned. slay. ✨
  • otherwise, a value of -1 shall be returned and errno set to indicate the error. 😔

🔥 ERRORS 🔥

the sem_close() function may fail if:

  • EINVAL — the sem argument is not a valid semaphore descriptor. 🚩

the following sections are informative. (translation: the tea is optional but still good 🍓)

💜 EXAMPLES 💜

None.

(yeah. nothing. iconic of them honestly. 💅)

🧚 APPLICATION USAGE 🧚

None.

🌟 RATIONALE 🌟

None.

🦋 FUTURE DIRECTIONS 🦋

None.

🫶 SEE ALSO 🫶

  • semctl()
  • semget()
  • semop()
  • sem_init()
  • sem_open()
  • sem_unlink()

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

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 .

and that's the whole page bestie!! 💅✨ this one came from the IEEE/The Open Group, dated 2017, and it's SEM_CLOSE(3POSIX) through and through — stay hydrated, close your semaphores, mwah 🫶🎀

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