Writes output to a stream under format control.
#include <stdio.h> int fprintf ( FILE *fp, const char *format, ... );
(IN) Points to the file to be written to.
(IN) Points to the format control string. See Print Format Control Strings.
(IN) Points to an argument for a conversion specifier. The number of arguments is determined by the format string.
If successful, returns the number of characters written. Otherwise, returns a negative value and sets errno to one of the following: