ilogb(3)
NAME
ilogb, ilogbf, ilogbl - get integer exponent of a floating-point 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 || _ISOC99_SOURCE; or cc -std=c99 ilogbf(), ilogbl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; 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.
CONFORMING TO
C99, POSIX.1-2001.
SEE ALSO
log(3), logb(3), significand(3)
COLOPHON
- This page is part of release 3.25 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/.