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**NAME**

ilogb, ilogbf, ilogbl - get integer exponent of a floating-point value

**SYNOPSIS**

#include<math.h>intilogb(doublex);intilogbf(floatx);intilogbl(longdoublex);Link with-lm. Feature Test Macro Requirements for glibc (seefeature_test_macros(7)):ilogb(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 500 || _XOPEN_SOURCE && _XOPEN_SOURCE_EXTENDED || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; orcc-std=c99ilogbf(),ilogbl(): _BSD_SOURCE || _SVID_SOURCE || _XOPEN_SOURCE >= 600 || _ISOC99_SOURCE || _POSIX_C_SOURCE >= 200112L; orcc-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 correspondinglogb(3) functions, cast toint.

**RETURN** **VALUE**

On success, these functions return the exponent ofx, as a signed integer. Ifxis zero, then a domain error occurs, and the functions returnFP_ILOGB0. Ifxis a NaN, then a domain error occurs, and the functions returnFP_ILOGBNAN. Ifxis negative infinity or positive infinity, then a domain error occurs, and the functions returnINT_MAX.

**ERRORS**

Seemath_error(7) for information on how to determine whether an error has occurred when calling these functions. The following errors can occur: Domain error:xis 0 or a NaN An invalid floating-point exception (FE_INVALID) is raised. These functions do not seterrnofor this case. Domain error:xis an infinity These functions do not seterrnoor 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 3.35 of the Linuxman-pagesproject. A description of the project, and information about reporting bugs, can be found at http://man7.org/linux/man- pages/. 2010-09-20 ILOGB(3)