# fmod

## PROLOG



           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.
    


## 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.
    


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