#include "apue.h"#include <errno.h>#include <fcntl.h>char	buf[500000];intmain(void){	int		ntowrite, nwrite;	char	*ptr;	ntowrite = read(STDIN_FILENO, buf, sizeof(buf));	fprintf(stderr, "read %d bytes\n", ntowrite);	set_fl(STDOUT_FILENO, O_NONBLOCK);	/* set nonblocking */	ptr = buf;	while (ntowrite > 0) {		errno = 0;		nwrite = write(STDOUT_FILENO, ptr, ntowrite);		fprintf(stderr, "nwrite = %d, errno = %d\n", nwrite, errno);		if (nwrite > 0) {			ptr += nwrite;			ntowrite -= nwrite;		}	}	clr_fl(STDOUT_FILENO, O_NONBLOCK);	/* clear nonblocking */	exit(0);}