fputc

fprintf

#include <stdio.h>int fprintf(FILE *stream, const char *format, ...);

The fprintf( ) function outputs the values of the arguments that comprise the argument list as specified in the format string to the stream pointed to by stream. The return value is the number of characters actually printed.
If an error occurs, a negative number is returned.

In C99, stream and format are qualified by restrict.

The operations of the format control string and commands are identical to those in printf( ); see printf( ) for a complete description.

Related functions are printf( ) and fscanf( ).