PTHREAD_C...R_GETCLOCK(3P)

💖 PTHREAD_C...R_GETCLOCK(3P) 💖

okay bestie, welcome to the POSIX Programmer's Manual — yes, that one, PTHREAD_C...R_GETCLOCK(3P). this page is lowkey iconic and it's all about clock attributes on condition variables. let's get into it 🕰️✨

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🚨 PROLOG 🚨

okay so real talk first, bestie:

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), or the interface might not be implemented on Linux at all. 😭

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✨ NAME ✨

pthread_condattr_getclock, pthread_condattr_setclock — get and set the clock selection condition variable attribute. yes, it's giving "read the clock attribute" and "write the clock attribute" 💅

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🌸 SYNOPSIS 🌸

#include <pthread.h>

int pthread_condattr_getclock(const pthread_condattr_t *restrict attr,
    clockid_t *restrict clock_id);
int pthread_condattr_setclock(pthread_condattr_t *attr,
    clockid_t clock_id);

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💜 DESCRIPTION 💜

so here's the vibe, bestie:

• pthread_condattr_getclock() shall obtain the value of the clock attribute from the attributes object referenced by attr. it's the reader, she reads 📖
• pthread_condattr_setclock() shall set the clock attribute in an initialized attributes object referenced by attr. it's the writer, she writes ✍️

and here's the spicy bit: if pthread_condattr_setclock() gets called with a clock_id argument that refers to a CPU-time clock, the call shall fail. no cap, it will not work for you 🙅‍♀️

now, what even is the clock attribute? it's the clock ID of the clock that shall be used to measure the timeout service of pthread_cond_timedwait(). and the default value of the clock attribute shall refer to the system clock. so if you don't touch it, you get the system clock, periodt 🕐

⚠️ the behavior is undefined if the value specified by the attr argument to pthread_condattr_getclock() or pthread_condattr_setclock() does not refer to an initialized condition variable attributes object. like, please initialize your stuff first bestie, this is not the vibe 💀

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🎀 RETURN VALUE 🎀

• if successful, pthread_condattr_getclock() shall return zero and store the value of the clock attribute of attr into the object referenced by the clock_id argument. otherwise, an error number shall be returned to indicate the error. ✨
• if successful, pthread_condattr_setclock() shall return zero; otherwise, an error number shall be returned to indicate the error. 🫶

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🔥 ERRORS 🔥

the pthread_condattr_setclock() function may fail if:

• EINVAL — the value specified by clock_id does not refer to a known clock, or is a CPU-time clock. ngl that's the "you gave me a weird clock" error 💅

🛑 these functions shall not return an error code of [EINTR]. like, don't even ask.

the following sections are informative — so they're the commentary track, not the rules 👑

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🌈 EXAMPLES 🌈

None. bestie there are literally zero examples here. the void. the nothingness. 🙈

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🦋 APPLICATION USAGE 🦋

None. also empty. we're keeping it mysterious ✨

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🧚 RATIONALE 🧚

so if an implementation detects that the value specified by the attr argument to pthread_condattr_getclock() or pthread_condattr_setclock() does not refer to an initialized condition variable attributes object, it is recommended that the function should fail and report an [EINVAL] error. recommended, bestie — like a soft launch of an error 🎀

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⭐ FUTURE DIRECTIONS ⭐

None. the future is a blank page and honestly, slay 💅

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👑 SEE ALSO 👑

go read these, they're the friend group:

• pthread_cond_destroy()
• pthread_cond_timedwait()
• pthread_condattr_destroy()
• pthread_condattr_getpshared()
• pthread_create()
• pthread_mutex_destroy()

and also the Base Definitions volume of POSIX.1‐2017, <pthread.h> 📚

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💖 COPYRIGHT 💖

okay legal bestie moment, here we go:

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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and that's the whole page bestie 🫶 this little gem came to you from IEEE/The Open Group, 2017 — go forth and measure your timeouts correctly, mwah 💋🌸