SEM_GETVALUE(3POSIX)

💖 SEM_GETVALUE 💖 — from the POSIX Programmer's Manual, bestie

okay so real talk, this page is part of the POSIX Programmer's Manual (3POSIX, she's iconic like that). quick vibe check before we dive in 👇

PROLOG: 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. so like, fr fr, check ur local manpage bestie, don't come for me 💀

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✨ NAME ✨

sem_getvalue — get the value of a semaphore

literally that's it, that's the whole job, she reads the number and tells u 🎀

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🌸 SYNOPSIS 🌸

#include <semaphore.h>

int sem_getvalue(sem_t *restrict sem, int *restrict sval);

two pointers, both restrict, no cap 💅

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🦋 DESCRIPTION 🦋

okay so sem_getvalue() shall update the location referenced by the sval argument to have the value of the semaphore referenced by sem, without affecting the state of the semaphore. like, she's just peeking. not touching. respectful queen 👑

and here's the tea: the updated value represents an actual semaphore value that occurred at some unspecified time during the call, but it need not be the actual value of the semaphore when it is returned to the calling process. so basically it's a snapshot, not a livestream 📸 not me getting a slightly stale number and being like "wait what"

if sem is locked, then the object to which sval points shall either be:

• set to zero, or
• set to a negative number whose absolute value represents the number of processes waiting for the semaphore at some unspecified time during the call.

so like if u see -3 it's giving "three lil guys are in the queue waiting" 😭 the ambiguity is real tho — she's allowed to just hand u a 0 and keep the mystery alive

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⭐ RETURN VALUE ⭐

upon successful completion, the sem_getvalue() function shall return a value of zero. slay. 🫶

otherwise, it shall return a value of -1 and set errno to indicate the error. not slay. 😔

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💀 ERRORS 💀

the sem_getvalue() function may fail if:

• EINVAL — the sem argument does not refer to a valid semaphore.

(yes bestie, "may", not "shall", read it and weep, that's the spec's whole vibe here 🙈)

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the following sections are informative. meaning: tea, not law ☕

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🌈 EXAMPLES 🌈

None.

(no examples, we're thriving on vibes alone apparently ✨)

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🎀 APPLICATION USAGE 🎀

None.

(nothing here either, the authors said "figure it out" 💅)

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🧚 RATIONALE 🧚

None.

(no reasoning given, she simply is 👑)

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🔥 FUTURE DIRECTIONS 🔥

None.

(future? unknown. we stay present. main character energy ⭐)

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💜 SEE ALSO 💜

• semctl()
• semget()
• semop()
• sem_post()
• sem_timedwait()
• sem_trywait()
• The Base Definitions volume of POSIX.1‐2017, <semaphore.h>

go read those too, iykyk 📚

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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, mwah 💋 shoutout to IEEE/The Open Group, 2017, for bringing us SEM_GETVALUE(3POSIX) — stay hydrated, check ur errno, and don't forget to lock ur semaphores 🌸💖🦋