ILOGB
Section: Linux Programmer's Manual (3)
Updated: 20130806
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NAME
ilogb, ilogbf, ilogbl  get integer exponent of a floatingpoint value
SYNOPSIS
#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 integer.
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 floatingpoint exception
(FE_INVALID)
is raised.

These functions do not set
errno
for this case.
 Domain error: x is an infinity


These functions do not set
errno
or raise an exception for this case.
ATTRIBUTES
Multithreading (see pthreads(7))
The
ilogb(),
ilogbf(),
and
ilogbl()
functions are threadsafe.
CONFORMING TO
C99, POSIX.12001.
SEE ALSO
log(3),
logb(3),
significand(3)
COLOPHON
This page is part of release 3.74 of the Linux
manpages
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/manpages/.
Index
 NAME

 SYNOPSIS

 DESCRIPTION

 RETURN VALUE

 ERRORS

 ATTRIBUTES

 Multithreading (see pthreads(7))

 CONFORMING TO

 SEE ALSO

 COLOPHON
