This manual page is part of the POSIX Programmer's Manual. The Linux implementation of this interface

       None.

       Portions of this text are reprinted and reproduced in electronic form from IEEE Std 1003.1-2017, Standard
       for Information  Technology  --  Portable  Operating  System  Interface  (POSIX),  The  Open  Group  Base
       Specifications  Issue  7, 2018 Edition, Copyright (C) 2018 by the Institute of Electrical and Electronics
       Engineers, Inc and The Open Group.  In the event of any discrepancy between this version and the original
       IEEE and The Open Group Standard, the original IEEE and The Open Group Standard is the referee  document.
       The original Standard can be obtained online at http://www.opengroup.org/unix/online.html .

       Any  typographical  or formatting errors that appear in this page are most likely to have been introduced
       during  the  conversion  of  the  source  files  to  man  page  format.  To  report  such   errors,   see
       https://www.kernel.org/doc/man-pages/reporting_bugs.html .

IEEE/The Open Group                                   2017                                    FPCLASSIFY(3POSIX)

       The  functionality  described  on  this  reference  page is aligned with the ISO C standard. Any conflict
       between the requirements described  here  and  the  ISO C  standard  is  unintentional.  This  volume  of
       POSIX.1‐2017 defers to the ISO C standard.

       The  fpclassify()  macro  shall classify its argument value as NaN, infinite, normal, subnormal, zero, or
       into another implementation-defined category.  First, an argument represented in a format wider than  its
       semantic  type  is  converted  to  its  semantic  type.  Then  classification is based on the type of the
       argument.

       No errors are defined.

       Thefollowingsectionsareinformative.

       None.

       None.

       fpclassify — classify real floating type

       This  manual  page  is part of the POSIX Programmer's Manual.  The Linux implementation of this interface
       may differ (consult the corresponding Linux manual page for details of Linux behavior), or the  interface
       may not be implemented on Linux.

       None.

       The fpclassify() macro shall return the value of the number classification macro appropriate to the value
       of its argument.

isfinite(), isinf(), isnan(), isnormal(), signbit()

       The Base Definitions volume of POSIX.1‐2017, <math.h>

       #include <math.h>

       int fpclassify(real-floating x);