FMOD(3)                    POSIX Programmer's Manual                   FMOD(3)



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

NAME
       fmod, fmodf, fmodl -- floating-point remainder value function

SYNOPSIS
       #include <math.h>

       double fmod(double _x, double _y);
       float fmodf(float _x, float _y);
       long double fmodl(long double _x, long double _y);

DESCRIPTION
       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.

       These functions shall return the floating-point remainder of the
       division of _x by _y.

       An application wishing to check for error situations should set errno
       to zero and call feclearexcept(FE_ALL_EXCEPT) before calling these
       functions. On return, if errno is non-zero or fetestexcept(FE_INVALID |
       FE_DIVBYZERO | FE_OVERFLOW | FE_UNDERFLOW) is non-zero, an error has
       occurred.

RETURN VALUE
       These functions shall return the value _x-_i*_y, for some integer _i such
       that, if _y is non-zero, the result has the same sign as _x and magnitude
       less than the magnitude of _y.

       If the correct value would cause underflow, and is not representable, a
       range error may occur, and fmod(), modf(), and fmodl() shall return
       0.0, or (if the IEC 60559 Floating-Point option is not supported) an
       implementation-defined value no greater in magnitude than DBL_MIN,
       FLT_MIN, and LDBL_MIN, respectively.

       If _x or _y is NaN, a NaN shall be returned, and none of the conditions
       below shall be considered.

       If _y is zero, a domain error shall occur, and a NaN shall be returned.

       If _x is infinite, a domain error shall occur, and a NaN shall be
       returned.

       If _x is +-0 and _y is not zero, +-0 shall be returned.

       If _x is not infinite and _y is +-Inf, _x shall be returned.

       If the correct value would cause underflow, and is representable, a
       range error may occur and the correct value shall be returned.

ERRORS
       These functions shall fail if:

       Domain Error
                   The _x argument is infinite or _y is zero.

                   If the integer expression (math__errhandling & MATH_ERRNO)
                   is non-zero, then errno shall be set to [EDOM].  If the
                   integer expression (math__errhandling & MATH_ERREXCEPT) is
                   non-zero, then the invalid floating-point exception shall
                   be raised.

       These functions may fail if:

       Range Error The result underflows.

                   If the integer expression (math__errhandling & MATH_ERRNO)
                   is non-zero, then errno shall be set to [ERANGE].  If the
                   integer expression (math__errhandling & MATH_ERREXCEPT) is
                   non-zero, then the underflow floating-point exception shall
                   be raised.

       The following sections are informative.

EXAMPLES
       None.

APPLICATION USAGE
       On error, the expressions (math__errhandling & MATH_ERRNO) and
       (math__errhandling & MATH_ERREXCEPT) are independent of each other, but
       at least one of them must be non-zero.

RATIONALE
       None.

FUTURE DIRECTIONS
       None.

SEE ALSO
       feclearexcept(), fetestexcept(), isnan()

       Section 4.20, Treatment of Error Conditions for Mathematical Functions,
       <math.h>

COPYRIGHT
       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                              FMOD(3)
