NAME¶

log2, log2f, log2l - base-2 logarithmic function

LIBRARY¶

Math library (libm, -lm)

SYNOPSIS¶

#include <math.h>

double log2(double x);
float log2f(float x);
long double log2l(long double x);

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).

ATTRIBUTES¶

For an explanation of the terms used in this section, see attributes(7).

STANDARDS¶

C11, POSIX.1-2008.

HISTORY¶

glibc 2.1. C99, POSIX.1-2001.

The variant returning double also conforms to SVr4, 4.3BSD.

SEE ALSO¶

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