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log2(3) — Linux manual page

log2(3)                  Library Functions Manuallog2(3)

NAME        top

       log2, log2f, log2l - base-2 logarithmic function

LIBRARY        top

       Math library (libm,-lm)

SYNOPSIS        top

#include <math.h>double log2(doublex);float log2f(floatx);long double log2l(long doublex);   Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):log2(),log2f(),log2l():           _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION        top

       These functions return the base-2 logarithm ofx.

RETURN VALUE        top

       On success, these functions return the base-2 logarithm ofx.       For special cases, including wherex is 0, 1, negative, infinity,       or NaN, seelog(3).

ERRORS        top

       Seemath_error(7) for information on how to determine whether an       error has occurred when calling these functions.       For a discussion of the errors that can occur for these functions,       seelog(3).

ATTRIBUTES        top

       For an explanation of the terms used in this section, seeattributes(7).       ┌──────────────────────────────────────┬───────────────┬─────────┐       │Interface│Attribute│Value│       ├──────────────────────────────────────┼───────────────┼─────────┤       │log2(),log2f(),log2l()             │ Thread safety │ MT-Safe │       └──────────────────────────────────────┴───────────────┴─────────┘

STANDARDS        top

       C11, POSIX.1-2008.

HISTORY        top

       glibc 2.1.  C99, POSIX.1-2001.       The variant returningdouble also conforms to SVr4, 4.3BSD.

SEE ALSO        top

cbrt(3),clog2(3),log(3),log10(3),sqrt(3)

COLOPHON        top

       This page is part of theman-pages (Linux kernel and C library       user-space interface documentation) project.  Information about       the project can be found at        ⟨https://www.kernel.org/doc/man-pages/⟩.  If you have a bug report       for this manual page, see       ⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.       This page was obtained from the tarball man-pages-6.15.tar.gz       fetched from       ⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on       2025-08-11.  If you discover any rendering problems in this HTML       version of the page, or you believe there is a better or more up-       to-date source for the page, or you have corrections or       improvements to the information in this COLOPHON (which isnot       part of the original manual page), send a mail to       man-pages@man7.orgLinux man-pages 6.15            2025-05-17log2(3)

Pages that refer to this page:log10(3), log(3)

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