ILOGB(3)                            Linux Programmer's Manual                            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 ||
           _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  func‐
       tions 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.

ATTRIBUTES
   Multithreading (see pthreads(7))
       The ilogb(), ilogbf(), and ilogbl() functions are thread-safe.

CONFORMING TO
       C99, POSIX.1-2001.

SEE ALSO
       log(3), logb(3), significand(3)

COLOPHON
       This page is part of release 3.74 of the Linux man-pages 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/man-pages/.



                                            2013-08-06                                   ILOGB(3)