semaphore.h(7POSIX)

💖 semaphore.h — a whole header, bestie 💖

okay so quick lil intro before we get into it: this page lives in the POSIX Programmer's Manual, and its whole name-and-number thing is semaphore.h(7POSIX). yes, section 7, POSIX, we love a crossover moment. 💅

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✨ PROLOG ✨

so like, real talk: this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ — so if you're on Linux, go read the matching Linux manual page for the actual tea on Linux behavior. orrr the interface might not even be implemented on Linux at all. 😭 no cap, check first.

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🦋 NAME 🦋

semaphore.h — semaphores, babe. that's it. that's the vibe. semaphores.

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🌸 SYNOPSIS 🌸

#include <semaphore.h>

literally just include the header and you're in. periodt.

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👑 DESCRIPTION 👑

okay so the <semaphore.h> header shall define the sem_t type — that's the one you use when you're out here performing semaphore operations. iconic.

and here's a fun lil detail: the semaphore may be implemented using a file descriptor 👀 — and in that case, applications are able to open up at least a total of {OPEN_MAX} files and semaphores. yes bestie, they share the budget. it's giving "we split the rent".

the <semaphore.h> header shall also define the symbolic constant SEM_FAILED, and its type shall be sem_t *. remember that one, she's important. 🎀

now the main event — the following shall be declared as functions, and they may also be defined as macros. function prototypes shall be provided. (so like, don't come for them if they're macros, that's allowed. 💀)

int    sem_close(sem_t *);
int    sem_destroy(sem_t *);
int    sem_getvalue(sem_t *restrict, int *restrict);
int    sem_init(sem_t *, int, unsigned);
sem_t *sem_open(const char *, int, ...);
int    sem_post(sem_t *);
int    sem_timedwait(sem_t *restrict, const struct timespec *restrict);
int    sem_trywait(sem_t *);
int    sem_unlink(const char *);
int    sem_wait(sem_t *);

look at that lineup. ten little legends. 🫶

one more thing, lowkey important: including the <semaphore.h> header may make visible symbols defined in the <fcntl.h> and <time.h> headers. so if you suddenly have extra symbols hanging around uninvited, that's why. they came with the semaphore. 🙈

heads up: the following sections are informative. so they're the commentary track, not the main plot.

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🌈 APPLICATION USAGE 🌈

None.

like literally none. the field is empty. nothing to see. moving on. 💀

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⭐ RATIONALE ⭐

None.

also empty. the reasoning section has no reasoning. it's giving minimalist. ✨

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🧚 FUTURE DIRECTIONS 🧚

None.

we don't know the future either. no notes. 🔮

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💜 SEE ALSO 💜

go peek at these headers, bestie:

• <fcntl.h>
• <sys_types.h>
• <time.h>

and then the System Interfaces volume of POSIX.1‐2017 girlies:

• sem_close()
• sem_destroy()
• sem_getvalue()
• sem_init()
• sem_open()
• sem_post()
• sem_timedwait()
• sem_trywait()
• sem_unlink()

(yeah sem_wait() isn't in that list. i know. i don't make the rules, i just read them. 😭)

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📜 COPYRIGHT 📜

okay so the legal bit, and it matters, so here it is properly:

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.

and this part is the real one — 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. that's not a vibe check, that's a fact check. 👑

the original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

also: 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!! 🎀 she was written by IEEE/The Open Group, dated 2017, and she answers to the name semaphore.h(7POSIX) — okay love you, bye, go lock something responsibly 💖✨🦋