#include <sys/types.h>
#include <sys/wait.h>
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>

int main( int argc, char* argv[] ){

	int pipefd[2];
	int retval = pipe( pipefd );
	if( retval == -1 ){
		perror("Could not create pipe");
		exit(-1);
	}

	pid_t child1, child2;

	//Create the first child
	child1 = fork();
	if( child1 == -1 ){
		perror("Could not create child1");
		exit(-1);
	}
	if( child1 == 0 ){ //Child process
		//This is the reader process
		close( pipefd[1] );

		dup2( pipefd[0], STDIN_FILENO );

		char* cmd = "grep";
		char* newArgv[ 3 ];
		newArgv[0] = cmd;
		newArgv[1] = "fork";
		newArgv[2] = NULL;
		
		execvp( cmd, newArgv );
	
		exit(0);
	}

	//Create the second child
        child2 = fork();
        if( child2 == -1 ){
                perror("Could not create child2");
                exit(-1);
        }
        if( child2 == 0 ){ //Child process
		//This is the writer process
		close( pipefd[0] );

		dup2( pipefd[1], STDOUT_FILENO );

		char* cmd = "ls";
		char* newArgv[ 3 ];
		newArgv[0] = cmd;
		newArgv[1] = "-l";
		newArgv[2] = NULL;

		execvp( cmd, newArgv );

		exit(0);
        }

	close( pipefd[0] );
	close( pipefd[1] );

	//Wait for both children to terminate before continuing
	waitpid( child1, NULL, 0 );
       	waitpid( child2, NULL, 0 );	




	return 0;
}