// file: ls_less.c
//
// Synopsis: Simple illustration of pipe between 2 processes
// 		from [Jumpstart].
//
// 	     Executes "ls" and pipes output to "less".
// 		(1) Creates pipe
// 		(2) Forks
// 		(3) Child: redirect output to pipe, then exec "ls"
// 		(4) Parent: redirect input to pipe, then exec "less"
//
//	REMARK: THIS PROGRAM WORKS ON BOTH CYGWIN and SOLARIS.
// Chee Yap

#include <unistd.h>
#include <stdio.h>

main()
{  
	
   int pid;
   int pipev[2];

   if (pipe(pipev) == -1)
	   perror("pipe");

   pid = fork();
   if (pid == 0) {
	   /* child */
	   char *argv[] = {"ls", "/etc", ".", NULL};
	   dup2(pipev[1], STDOUT_FILENO); // redirect output of ls
	   close(pipev[0]); close(pipev[1]);
	   execvp("ls", argv);
	   perror("ls");
   } else if (pid >0) {
	   /* parent */
	   dup2(pipev[0], STDIN_FILENO); // redirect input of less
	   close(pipev[0]); close(pipev[1]);
	   execlp("less", "less", NULL);
	   perror("less");
   } else
	   perror("fork");

   printf("finish\n");
   exit(0);
}