sem_close(3)

✨ sem_close(3) ✨

okay bestie, so this is a page from the Library Functions Manual, and it's literally about closing a named semaphore. yes, the polite goodbye one. let's get into it 💅

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💖 NAME 💖

sem_close — close a named semaphore

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📚 LIBRARY 📚

POSIX threads library, aka libpthread, and you link it with -lpthread. that's the whole vibe.

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🎀 SYNOPSIS 🎀

#include <semaphore.h>

int sem_close(sem_t *sem);

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🦋 DESCRIPTION 🦋

so sem_close() closes the named semaphore that sem points at. what that actually does is it lets the system free up any resources that it had allocated to the calling process for that specific semaphore. like, you're done with it, you're releasing your claim, the resources get to go home. 🫶

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👑 RETURN VALUE 👑

• on a slay (success), sem_close() returns 0 ✨
• on an uh oh (error), -1 is returned, and errno gets set to tell you what went wrong.

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💀 ERRORS 💀

• EINVAL — sem is not a valid semaphore. that's it, that's the only one, but it's giving "you handed me garbage".

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🌈 ATTRIBUTES 🌈

if you want the full explanation of the terms floating around in this section, go peek at attributes(7) — it's the receipts. 👀

• Interface: sem_close()
• Attribute: Thread safety
• Value: MT-Safe

so yeah, sem_close() is MT-Safe, which is lowkey iconic of it.

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⭐ STANDARDS ⭐

POSIX.1-2008. certified, no notes, periodt.

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🧚 HISTORY 🧚

POSIX.1-2001. it's been around. vintage, even. main character energy since the early aughts.

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🍓 NOTES 🍓

okay this part is important so listen up bestie: all open named semaphores get automatically closed when the process terminates, or upon execve(2). so the system has your back even if you forget. still, do it yourself, it's cute. 🙈

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💜 SEE ALSO 💜

• sem_getvalue(3)
• sem_open(3)
• sem_post(3)
• sem_unlink(3)
• sem_wait(3)
• sem_overview(7)

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and that's the whole page, no cap 💖 this gorgeous little writeup came from Linux man-pages 6.20, dated 2026-02-08 — shoutout to the man-pages girlies for keeping us fed. go close a semaphore responsibly, mwah 🎀✨