ILOGBSection: Linux Programmer's Manual (3)
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NAMEilogb, ilogbf, ilogbl - get integer exponent of a floating-point value
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)):
_BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _ISOC99_SOURCE; or
ilogbf(), ilogbl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE; or cc -std=c99
DESCRIPTIONThese 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 VALUEOn 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.
ERRORSSee 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 TOC99, POSIX.1-2001.
SEE ALSOlog(3), logb(3), significand(3)
COLOPHONThis page is part of release 3.21 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/.