LOG2Section: Linux Programmer's Manual (3)
Index | Return to Main Contents
NAMElog2, log2f, log2l - base-2 logarithmic function
#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():
_XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTIONThese functions return the base 2 logarithm of x.
RETURN VALUEOn 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).
ERRORSSee 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).
VERSIONSThese functions first appeared in glibc in version 2.1.
ATTRIBUTESFor an explanation of the terms used in this section, see attributes(7).
|log2(), log2f(), log2l()||Thread safety||MT-Safe|
CONFORMING TOC99, POSIX.1-2001, POSIX.1-2008.
SEE ALSOcbrt(3), clog2(3), log(3), log10(3), sqrt(3)
COLOPHONThis page is part of release 4.04 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 http://www.kernel.org/doc/man-pages/.
Return to Main Contents