text: NAMEdrem - floating-point remainder function
  SYNOPSIS
  #include <math.h> double drem(double x, double y);
  DESCRIPTIONThe drem() function computes the remainder of dividing x by y. The return value is x - n * y, where n is the quotient of x / y, rounded to the nearest integer. If the quotient is 1/2, it is rounded to the even number.
  RETURN VALUEThe drem() function returns the remainder, unless y is zero, when the function fails and errno is set.
  ERRORS
  - EDOM
  - The denominator y is zero.
  CONFORMING TOBSD 4.3
  SEE ALSOfmod(3)
  Important: Use the man command (% man) to see how a command is used on your particular computer.
  >> Linux/Unix Command Library