# logb(3) [osx man page]

```LOGB(3) 						   BSD Library Functions Manual 						   LOGB(3)

NAME
logb -- return exponent as a floating-point number

SYNOPSIS
#include <math.h>

double
logb(double x);

long double
logbl(long double x);

float
logbf(float x);

DESCRIPTION
The logb() functions return the exponent of x, represented as a floating-point number.

SPECIAL VALUES
logb(+-0) returns -infinity and raises the "divide-by-zero" floating-point exception.

logb(+-infinity) returns +infinity.

VECTOR OPERATIONS
If you need to apply the logb() functions to SIMD vectors or arrays, using the following functions provided by the Accelerate.framework may
give significantly better performance:

#include <Accelerate/Accelerate.h>

vFloat vlogbf(vFloat x);
void vvlogbf(float *y, const float *x, const int *n);
void vvlogb(double *y, const double *x, const int *n);

ilogb(3) log(3) math(3)

STANDARDS
The logb() functions conform to ISO/IEC 9899:2011.

BSD								  August 21, 2012							       BSD```

## Check Out this Related Man Page

```ILOGB(3)						   BSD Library Functions Manual 						  ILOGB(3)

NAME
ilogb, ilogbf, ilogbl, logb, logbf, logbl -- extract exponent

LIBRARY
Math Library (libm, -lm)

SYNOPSIS
#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);

DESCRIPTION
ilogb(), ilogbf() and ilogbl() return x's exponent in integer format.  ilogb(+-infinity) returns INT_MAX, ilogb(+-NaN) returns FP_ILOGBNAN,
and ilogb(0) returns FP_ILOGB0.

logb(x), logbf(x), and logbl(x) return x's exponent in floating-point format with the same precision as x.  logb(+-infinity) returns +infin-
ity, and logb(0) returns -infinity with a division by zero exception.

frexp(3), ieee(3), math(3), scalbn(3)

STANDARDS
The ilogb(), ilogbf(), ilogbl(), logb(), logbf(), and logbl() routines conform to ISO/IEC 9899:1999 (``ISO C99'').  The latter three imple-
ment the logb function recommended by IEEE Std 754-1985.

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

BSD								 December 16, 2007							       BSD```
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