**ilogbl**

#include <math.h>
int ilogb(double x);
int ilogbf(float x);
int ilogbl(long double x);
Link with -lm.
Feature Test Macro Requirements for glibc (see **feature_test_macros(7)**):
ilogb():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 ||
_XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE ||
_POSIX_C_SOURCE >= 200112L;
or cc -std=c99
ilogbf(), ilogbl():
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 ||
_ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L;
or cc -std=c99
DESCRIPTION
These functions return the exponent part of their argument as a signed
integer. When no error occurs, these functions are equivalent to the
corresponding **logb(3)** functions, cast to int.
RETURN VALUE
On success, these functions return the exponent of x, as a signed inte-
ger.
If x is zero, then a domain error occurs, and the functions return
FP_ILOGB0.
If x is a NaN, then a domain error occurs, and the functions return
FP_ILOGBNAN.
If x is negative infinity or positive infinity, then a domain error
occurs, and the functions return INT_MAX.
ERRORS
See **math_error(7)** for information on how to determine whether an error
has occurred when calling these functions.
The following errors can occur:
Domain error: x is 0 or a NaN
An invalid floating-point exception (FE_INVALID) is raised, and
errno is set to EDOM (but see BUGS).
Domain error: x is an infinity
An invalid floating-point exception (FE_INVALID) is raised, and
errno is set to EDOM (but see BUGS).
ATTRIBUTES
For an explanation of the terms used in this section, see
tation of these functions:
* The domain error case where x is 0 or a NaN did not cause errno to
be set or (on some architectures) raise a floating-point exception.
* The domain error case where x is an infinity did not cause errno to
be set or raise a floating-point exception.
SEE ALSO
**log(3)**, **logb(3)**, **significand(3)**
COLOPHON
This 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/.
2015-04-19 **ILOGB(3)**

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