#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <errno.h>

int main(int argc, char **argv)
{
	int     	o;
	char		*buffer="AAAA";

	if ( -1 == ( o = open( argv[1], O_WRONLY|O_CREAT, 0666)))
	{
		perror("open");
		return 1;
	}

	if ( -1 == lseek (o, (off_t) atol(argv[2]) - 4, SEEK_SET))
		perror("lseek");

	write( o, buffer, 4 );
	close(o);
}