# ilogb(3) [osf1 man page]

```ilogb(3)						     Library Functions Manual							  ilogb(3)

NAME
ilogb - Returns an unbiased exponent

LIBRARY
Math Library (libm.a)

SYNOPSIS
#include <math.h>

int ilogb  (double x); int ilogbf (float  x); int ilogbl  (long double x);

STANDARDS
Interfaces documented on this reference page conform to industry standards as follows:

ilogb():  XPG4-UNIX

DESCRIPTION
The  ilogb(),  ilogbf(),  and  ilogbl() functions return the integral part of the base r  logarithm of (|x|) as a signed integral value for
non-zero x, where r is the radix of the machine's floating point arithmetic.

The following table describes function behavior in response to exceptional arguments:

---------------------------------------------------------------------
Function 		    Exceptional Argument   Routine Behavior
---------------------------------------------------------------------
ilogb(), ilogbf() ilogbl()   |x| = infinity	   INT_MAX
ilogb(), ilogbf() ilogbl()   x = 0, NaN		   INT_MIN
---------------------------------------------------------------------
delim off

ilogb(3)```

## 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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