/*  pipedemo.c	*
 * 创建管道并使用管道来向自己发送数据
 */
#include	<stdio.h>
#include	<unistd.h>

main()
{
	int	len, i, apipe[2];	/* two file descriptors */
	char	buf[BUFSIZ];		/* for reading end	*/

	/* get a pipe */
	if ( pipe ( apipe ) == -1 ){
		perror("could not make pipe");
		exit(1);
	}
	printf("Got a pipe! It is file descriptors: { %d %d }\n", 
							apipe[0], apipe[1]);

	/* read from stdin, write into pipe, read from pipe, print */

	while ( fgets(buf, BUFSIZ, stdin) ){
		len = strlen( buf );
		if (  write( apipe[1], buf, len) != len ){	/* send	*/
			perror("writing to pipe");		/* down */
			break;					/* pipe */
		}
		for ( i = 0 ; i<len ; i++ )                     /* wipe	*/
			buf[i] = 'X' ;
		len = read( apipe[0], buf, BUFSIZ ) ;		/* read */
		if ( len == -1 ){				/* from */
			perror("reading from pipe");		/* pipe */
			break;
		}
		if ( write( 1 , buf, len ) != len ){		/* send  */
			perror("writing to stdout");		/* to    */
			break;					/* stdout */
		}
	}
}