$B%W%m%;%9$H%Q%$%W(B

$B"!(Bdup()

dup() $B$h$j$b!"(Bdup2() $B$NJ}$,JXMx$G$"$k!#(B

----------------------------------------------------------------------
   1:	/*
   2:	        pipe-rw.c -- pipe() $B$H(B dup() $B$r;H$C$?%W%m%0%i%`(B
   3:	        ~yas/syspro/proc/pipe-rw.c
   4:	        $Header: /home/lab2/OS/yas/syspro/proc/RCS/pipe-rw-dup.c,v 1.7 2001/05/06 13:13:22 yas Exp $
   5:	        Start: 1997/05/26 20:43:29
   6:	*/
   7:	
   8:	#include <stdio.h>
   9:	#include <unistd.h>
  10:	
  11:	extern  void parent( int fildes[2] );
  12:	extern  void child( int fildes[2] );
  13:	
  14:	main()
  15:	{
  16:	    int fildes[2] ;
  17:	    pid_t pid ;
  18:	
  19:	        if( pipe(fildes) == -1)
  20:	        {
  21:	            perror("pipe");
  22:	            exit( 1 );
  23:	        }
  24:	        /* fildes[0] -- $BFI$_9~$_MQ(B
  25:	         * fildes[1] -- $B=q$-9~$_MQ(B
  26:	         */
  27:	        if( (pid=fork()) == 0 )
  28:	        {
  29:	            child( fildes );
  30:	        }
  31:	        else if( pid > 0 )
  32:	        {
  33:	            parent( fildes );
  34:	        }
  35:	        else
  36:	        {
  37:	            perror("fork");
  38:	            exit( 1 );
  39:	        }
  40:	}
  41:	
  42:	void parent( int fildes[2] )
  43:	{
  44:	    char *p, c ;
  45:	        close( fildes[0] );
  46:	        close( 1 );         /* $BI8=`=PNO$r%Q%$%W$K@ZBX$($k(B */
  47:	        dup( fildes[1] );
  48:	        close( fildes[1] );
  49:	
  50:	        p = "hello,world\n" ;
  51:	        while( *p )
  52:	        {
  53:	            c = *p ++ ;
  54:	            write( 1,&c,1 );
  55:	        }
  56:	        close( 1 );
  57:	}
  58:	
  59:	void child( int fildes[2] )
  60:	{
  61:	    char c, c2 ;
  62:	        close( fildes[1] );
  63:	        close( 0 );         /* $BI8=`F~NO$r%Q%$%W$K@ZBX$($k(B */
  64:	        dup( fildes[0] );
  65:	        close( fildes[0] );
  66:	
  67:	        while( read(0,&c,1) >0 )
  68:	        {
  69:	            c2 = toupper(c);
  70:	            write( 1, &c2, 1 );
  71:	        }
  72:	        close( 0 );
  73:	}
----------------------------------------------------------------------

----------------------------------------------------------------------
% ./pipe-rw-dup 
HELLO,WORLD
% 
----------------------------------------------------------------------