sendfile()시스템 콜 이렇게 이용하는거 맞나요??

#include <fcntl.h>
#include <stdlib.h>
#include <stdio.h>
#include <sys/sendfile.h>
#include <sys/stat.h>
#include <sys/types.h>
#include <unistd.h>
int main(int argc, char *argv[])
{
	int 					read_fd, write_fd;
	struct stat		stat_buf;
	off_t				offset = 0;
 
	read_fd = open(argv[1], O_RDONLY);
	fstat(read_fd, &stat_buf);
	write_fd = open(argv[2], O_WRONLY | O_CREAT, stat_buf.st_mode);
 
	sys_sendfile(write_fd, read_fd, &offset, stat_buf.st_size);
 
	close(read_fd);
	close(write_fd);
	return 0;
}