LOG10(3P)

💖 LOG10(3P) — POSIX Programmer's Manual 💖

okay bestie, so this is log10(3P) from the POSIX Programmer's Manual, and we're about to make base-10 logarithms the moment of your day. sit down, grab a strawberry, let's go 🍓✨

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🌸 PROLOG 🌸

okay so real talk first: 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 details on Linux behavior), or honestly the interface may not be implemented on Linux at all. no cap. 🙈

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✨ NAME ✨

log10, log10f, log10l — the base 10 logarithm function, she's here, she's iconic 💅

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🦋 SYNOPSIS 🦋

#include <math.h>

double log10(double x);
float log10f(float x);
long double log10l(long double x);

three flavors, all serving the same energy at different precisions, we love to see it 👑

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💜 DESCRIPTION 💜

the functionality described on this reference page is aligned with the ISO C standard. if there's any conflict between the requirements described here and the ISO C standard, that's unintentional — this volume of POSIX.1‐2017 defers to the ISO C standard, periodt.

these functions shall compute the base 10 logarithm of their argument x, log10(x).

okay so if your application wants to check for error situations (valid, we respect the paranoia 💅), you should set errno to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these functions. then on return, if errno is non-zero or fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has occurred. boom, that's the vibe check right there. ✅

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🔥 RETURN VALUE 🔥

upon successful completion, these functions shall return the base 10 logarithm of x. slay.

• if x is ±0, a pole error shall occur, and log10(), log10f(), and log10l() shall return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively. 😭
• for finite values of x that are less than 0, or if x is -Inf, a domain error shall occur, and either a NaN (if supported) or an implementation-defined value shall be returned.
• if x is NaN, a NaN shall be returned.
• if x is 1, +0 shall be returned.
• if x is +Inf, +Inf shall be returned. main character behavior fr fr ✨

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💀 ERRORS 💀

these functions shall fail if:

• Domain Error — the finite value of x is negative, or x is -Inf.

if the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [EDOM]. if the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the invalid floating-point exception shall be raised.

• Pole Error — the value of x is zero.

if the integer expression (math_errhandling & MATH_ERRNO) is non-zero, then errno shall be set to [ERANGE]. if the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the divide-by-zero floating-point exception shall be raised.

the following sections are informative — like, they're the bonus content, not the rules 📖

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🎀 EXAMPLES 🎀

None.

(ikr. nothing. the audacity 😭 but we respect it.)

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🌈 APPLICATION USAGE 🌈

on error, the expressions (math_errhandling & MATH_ERRNO) and (math_errhandling & MATH_ERREXCEPT) are independent of each other, but at least one of them must be non-zero. they're giving separate but equally important besties 🫶

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🧚 RATIONALE 🧚

None.

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⭐ FUTURE DIRECTIONS ⭐

None.

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👑 SEE ALSO 👑

• feclearexcept()
• fetestexcept()
• isnan()
• log()
• pow()

the Base Definitions volume of POSIX.1‐2017, Section 4.20, Treatment of Error Conditions for Mathematical Functions, <math.h>

go read those, 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 — like, they're the final boss, no arguments. 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, IEEE/The Open Group, 2017, LOG10(3P) — thanks for reading, go compute some base-10 logs and live your truth 💖✨🎀🦋🌸💅🫶