Manual Pages  — ILOGB

ilogb, ilogbf, ilogbl, logb, logbf, logbl – extract exponent

LIBRARY SYNOPSIS DESCRIPTION SEE ALSO STANDARDS HISTORY

Math Library (libm, -lm)

#include <math.h>

int
ilogb(double x);

int
ilogbf(float x);

int
ilogbl(long double x);

double
logb(double x);

float
logbf(float x);

long double
logbl(long double x);

ilogb(), ilogbf() and ilogbl() return x, Ns, 's, exponent in integer format. ilogb(±∞) returns INT_MAX, ilogb(±NaN) returns FP_ILOGBNAN, and ilogb() returns FP_ILOGB0.

logb(x), logbf(x), and logbl(x) return x, Ns, 's, exponent in floating-point format with the same precision as x. logb(±∞) returns +∞, and logb() returns -∞ with a division by zero exception.

The ilogb(), ilogbf(), ilogbl(), logb(), logbf(), and logbl() routines conform to ISO/IEC 9899:1999 ("ISO C99"). The latter three implement the logb function recommended by -ieee754.

Function	First Appeared In
logb()
	BSD 4.3
ilogb()
	FreeBSD 1.1.5
ilogbf()
	FreeBSD 2.0
logbf()
	FreeBSD 2.0
ilogbl()
	FreeBSD 5.4
logbl()
	FreeBSD 8.0