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2017-09-15
Aliases: log2f(3), log2f(3), log2f(3), log2f(3), log2f(3), log2f(3), log2l(3), log2l(3), log2l(3), log2l(3), log2l(3), log2l(3)

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Manual pages about using GNU/Linux for development

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Linux kernel and C library user-space interface documentation

NAME

log2, log2f, log2l - base-2 logarithmic function

SYNOPSIS

#include <math.h>

double log2(double x); float log2f(float x); long double log2l(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see feature_test_macros(7)):
log2(), log2f(), log2l():
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L

DESCRIPTION

These functions return the base 2 logarithm of x.

RETURN VALUE

On success, these functions return the base 2 logarithm of x.
For special cases, including where x is 0, 1, negative, infinity, or NaN, see log(3).

ERRORS

See math_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, see log(3).

VERSIONS

These functions first appeared in glibc in version 2.1.

ATTRIBUTES

For an explanation of the terms used in this section, see attributes(7).
Interface Attribute Value
Thread safety MT-Safe

CONFORMING TO

C99, POSIX.1-2001, POSIX.1-2008.
The variant returning double also conforms to SVr4, 4.3BSD.

COLOPHON

This page is part of release 5.00 of the Linux man-pages project. A description of the project, information about reporting bugs, and the latest version of this page, can be found at https://www.kernel.org/doc/man-pages/.

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