_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 floating-point 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.

This page is part of release 3.27 of the Linux
man-pages
project.
A description of the project,
and information about reporting bugs,
can be found at
http://www.kernel.org/doc/man-pages/.