SEM_UNLINK(3P)

💖 SEM_UNLINK(3P) 💖

okay bestie, so this is a page from the POSIX Programmer's Manual, and before we even get into it there's a little disclaimer you need to read, no skimming, i'm watching you 🫶

🚨 PROLOG 🚨

This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface may differ — so go consult the corresponding Linux manual page for the actual deets on Linux behavior. Or, plot twist, the interface may not be implemented on Linux at all. 😭

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✨ NAME ✨

sem_unlink — remove a named semaphore 💅

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🌸 SYNOPSIS 🌸

#include <semaphore.h>

int sem_unlink(const char *name);

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💫 DESCRIPTION 💫

So the sem_unlink() function shall remove the semaphore named by the string name. that's the whole vibe. 🎀

But here's the part where it gets interesting, bestie — if that semaphore named by name is currently referenced by other processes, then sem_unlink() shall have no effect on the state of the semaphore. like, it just... doesn't touch it. nothing happens. iconic behavior honestly.

And if one or more processes have the semaphore open when sem_unlink() gets called? Then destruction of the semaphore is postponed until all references to the semaphore have been destroyed by calls to sem_close(), _exit(), or exec. it's giving "you can't sit with us until everyone leaves" 😌

Also! Calls to sem_open() to recreate or reconnect to the semaphore refer to a new semaphore after sem_unlink() is called. brand new. fresh start. main character energy. ✨

And the last little detail: the sem_unlink() call shall not block until all references have been destroyed. it shall return immediately. no waiting around, she's busy, she has places to be. 💅

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🔥 RETURN VALUE 🔥

Upon successful completion, the sem_unlink() function shall return a value of 0. slay. 🎉

Otherwise (and this is the not-slay part 😭), the semaphore shall not be changed and the function shall return a value of -1 and set errno to indicate the error.

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💀 ERRORS 💀

The sem_unlink() function shall fail if:

• EACCES — Permission is denied to unlink the named semaphore. rude, honestly. 🙈
• ENOENT — The named semaphore does not exist. it's not there bestie, it never was. 💀

The sem_unlink() function may fail if:

• ENAMETOOLONG — The length of the name argument exceeds {_POSIX_PATH_MAX} on systems that do not support the XSI option, or exceeds {_XOPEN_PATH_MAX} on XSI systems, or has a pathname component that is longer than {_POSIX_NAME_MAX} on systems that do not support the XSI option, or longer than {_XOPEN_NAME_MAX} on XSI systems.

okay important caveat though: a call to sem_unlink() with a name argument that contains the same semaphore name as was previously used in a successful sem_open() call shall not give an [ENAMETOOLONG] error. so don't let that one scare you. 🫶

The following sections are informative.

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🌈 EXAMPLES 🌈

None. 💀

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🦋 APPLICATION USAGE 🦋

None. 💀

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🧚 RATIONALE 🧚

None. 💀

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⭐ FUTURE DIRECTIONS ⭐

A future version might require the sem_open() and sem_unlink() functions to have semantics similar to normal file system operations. so like... watch this space i guess? 👀

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👑 SEE ALSO 👑

• semctl()
• semget()
• semop()
• sem_close()
• sem_open()

The Base Definitions volume of POSIX.1‐2017, <semaphore.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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okay that's the whole page bestie, hope you ate it up 🍓

this one came to you courtesy of IEEE/The Open Group, 2017 — yeah, the SEM_UNLINK(3P) page, POSIX Programmer's Manual vibes, drop date 2017 ✨

now go unlink something. responsibly. 💅🦋