CLOCK(3P)

🌸 CLOCK(3P) — bestie edition 🌸

okay so this one's from the POSIX Programmer's Manual, section 3P, and it's literally called CLOCK. it's giving "how much CPU did my lil program eat" energy and honestly? obsessed. 💅

✨ PROLOG ✨

so like, real talk before we even start — this manual page is part of the POSIX Programmer's Manual. the Linux implementation of this interface may differ (so consult the corresponding Linux manual page for details on Linux behavior), or the interface may not even be implemented on Linux at all. 🙈 no cap, check first.

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💖 NAME 💖

clock — report CPU time used 🕐✨

🎀 SYNOPSIS 🎀

#include <time.h>

clock_t clock(void);

🦋 DESCRIPTION 🦋

okay so first things first, bestie: the functionality described on this reference page is aligned with the ISO C standard. any conflict between the requirements described here and the ISO C standard is unintentional — like, nobody's trying to start drama. this volume of POSIX.1‐2017 defers to the ISO C standard. periodt. 👑

now the actual tea: the clock() function shall return the implementation's best approximation to the processor time used by the process since the beginning of an implementation-defined era related only to the process invocation. that's the whole vibe. 🌈

💜 RETURN VALUE 💜

so to determine the time in seconds, the value returned by clock() should be divided by the value of the macro CLOCKS_PER_SEC. and CLOCKS_PER_SEC is defined to be one million in <time.h>. (one million!! she's fancy like that 💅)

and if the processor time used is not available or its value cannot be represented, the function shall return the value (clock_t)-1. 😭

⭐ ERRORS ⭐

No errors are defined.

(and the following sections are informative, jsyk 👀)

🌸 EXAMPLES 🌸

None.

...yeah. nothing. it's giving minimalism. 🫶

🌺 APPLICATION USAGE 🌺

okay bestie this part actually matters, listen up:

in programming environments where clock_t is a 32-bit integer type and CLOCKS_PER_SEC is one million, clock() will start failing in less than 36 minutes of processor time for signed clock_t, or 72 minutes for unsigned clock_t. 💀 that's it. that's the whole window. applications intended to be portable to such environments should use times() instead (or clock_gettime() with CLOCK_PROCESS_CPUTIME_ID, if supported).

so basically: if you're on a 32-bit clock_t situation, your clock hits the ceiling in under an hour and just gives up. not her fault, but like, plan accordingly. 🙈

and in order to measure the time spent in a program, clock() should be called at the start of the program and its return value subtracted from the value returned by subsequent calls. (start value, end value, subtract, slay. ➖✨) the value returned by clock() is defined for compatibility across systems that have clocks with different resolutions. and the resolution on any particular system need not be to microsecond accuracy. so don't come for her about precision, she's doing her best. 🎀

💫 RATIONALE 💫

None.

🔮 FUTURE DIRECTIONS 🔮

None.

👑 SEE ALSO 👑

asctime(), clock_getres(), ctime(), difftime(), gmtime(), localtime(), mktime(), strftime(), strptime(), time(), times(), utime()

the Base Definitions volume of POSIX.1‐2017, <time.h> 📚

🌈 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. (so if there's beef, the original wins, no debate 🫡) 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!! brought to you by IEEE/The Open Group, 2017 — mwah, thanks for the lore, sending you the biggest forehead kiss 💖🎀✨