ILOGB(3) Linux Programmer's Manual ILOGB(3)

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

SYNOPSIS
       #include 

       int ilogb(double x);
       int ilogbf(float x);
       int ilogbl(long double x);

       Link with -lm.

   Feature Test Macro Requirements for glibc (see featuretestmacros(7)):

       ilogb():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 500 ||
           XOPENSOURCE && XOPENSOURCEEXTENDED || ISOC99SOURCE ||
           POSIXCSOURCE >= 200112L;
           or cc -std=c99
       ilogbf(), ilogbl():
           BSDSOURCE || SVIDSOURCE || XOPENSOURCE >= 600 ||
           ISOC99SOURCE || POSIXCSOURCE >= 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 inte‐
       ger.

       If  x  is  zero,  then  a domain error occurs, and the functions return
       FPILOGB0.

       If x is a NaN, then a domain error occurs,  and  the  functions  return
       FPILOGBNAN.

       If  x  is  negative  infinity or positive infinity, then a domain error
       occurs, and the functions return INTMAX.

ERRORS
       See matherror(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 (FEINVALID) 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
       For  an  explanation  of  the  terms  used   in   this   section,   see
       attributes(7).

       ┌────────────────────────────┬───────────────┬─────────┐
       │Interface                   │ Attribute     │ Value   │
       ├────────────────────────────┼───────────────┼─────────┤
       │ilogb(), ilogbf(), ilogbl() │ Thread safety │ MT-Safe │
       └────────────────────────────┴───────────────┴─────────┘
CONFORMING TO
       C99, POSIX.1-2001.

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

COLOPHON
       This  page  is  part of release 3.53 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/.



                                  2010-09-20                          ILOGB(3)