# ilogb(3m) [sunos man page]

```ilogb(3M)						  Mathematical Library Functions						 ilogb(3M)

NAME
ilogb, ilogbf, ilogbl - return an unbiased exponent

SYNOPSIS
cc [ flag... ] file... -lm [ library... ]
#include <math.h>

int ilogb(double x);

int ilogbf(float x);

int ilogbl(long double x);

DESCRIPTION
These  functions  return  the exponent part of their argument x.  Formally, the return value is the integral part of  logr| x | as a signed
integral value, for non-zero x, where r is the radix of the machine's floating point arithmetic, , which is the value of FLT_RADIX  defined
in <float.h>.

RETURN VALUES
Upon  successful  completion,  these  functions return the exponent part of x as a signed integer value. They are equivalent to calling the
corresponding logb(3M) function and casting the returned value to type int.

If x is 0, the value FP_ILOGB0 is returned. For SUSv3-conforming applications (see standards(5)), a domain error occurs.

If x is +-Inf, the value INT_MAX is returned. For SUSv3-conforming applications, a domain error occurs.

If x is NaN, the value FP_ILOGBNAN is returned. For SUSv3-conforming applications, a domain error occurs.

ERRORS
These functions will fail if:

Domain Error    The x argument is zero, NaN, or +-Inf.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, then the  invalid  floating-point  exception	is
raised.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

SunOS 5.10							    1 Nov 2003								 ilogb(3M)```

## Check Out this Related Man Page

```logb(3M)						  Mathematical Library Functions						  logb(3M)

NAME
logb, logbf, logbl - radix-independent exponent

SYNOPSIS
cc [ flag... ] file... -lm [ library... ]
#include <math.h>

double logb(double x);

float logbf(float x);

long double logbl(long double x);

DESCRIPTION
These  functions compute the exponent of x, which is the integral part of logr |x|, as a signed floating point value, for non-zero x, where
r is the radix of the machine's floating-point arithmetic, which is the value of FLT_RADIX defined in the <float.h> header.

RETURN VALUES
Upon successful completion, these functions return the exponent of x.

If x is subnormal:

o  For SUSv3-conforming applications (see standards(5)), the exponent of x as if x were normalized is returned.

o  Otherwise, -1022, -126, and -16382 are returned for logb(), logbf(), and logbl(), respectively.

If x is +-0, a pole error occurs and logb(), logbf(), and logbl() return -HUGE_VAL, -HUGE_VALF, and -HUGE_VALL, respectively.

If x is NaN, a NaN is returned.

If x is +-Inf, +Inf is returned.

ERRORS
These functions will fail if:

Pole Error      The value of x is +-0.

If the integer expression (math_errhandling & MATH_ERREXCEPT) is non-zero, the divide-by-zero floating-point  exception	is
raised.

The logb() function sets errno to EDOM if the value of x is 0.

USAGE
An  application	wanting  to  check  for  exceptions should call feclearexcept(FE_ALL_EXCEPT) before calling these functions. On return, if
fetestexcept(FE_INVALID | FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an exception  has  been  raised.  An  application  should
either examine the return value or check the floating point exception flags to detect exceptions.

An  application	can  also  set	errno  to 0 before calling logb(). On return, if errno is non-zero, an error has occurred. The logbf() and
logbl() functions do not set errno.

ATTRIBUTES
See attributes(5) for descriptions of the following attributes:

+-----------------------------+-----------------------------+
|      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
+-----------------------------+-----------------------------+
|Interface Stability	     |Standard			   |
+-----------------------------+-----------------------------+
|MT-Level		     |MT-Safe			   |
+-----------------------------+-----------------------------+

feclearexcept(3M), fetestexcept(3M), ilogb(3M), math.h(3HEAD), matherr(3M), scalb(3M), attributes(5), standards(5)

SunOS 5.10							    1 Nov 2003								  logb(3M)```
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