Programming

int main (void)
{
    pid_t pid;
    int pipe_in[2];
    int pipe_out[2];
    char buffer[800];

    /* Create the pipe.  */
    pipe (pipe_in);
    pipe (pipe_out);

    /* Create the child process.  */
    pid = vfork ();
    if (pid == (pid_t) 0) /* child 1 */
    {
		/*close unneeded*/
                close(pipe_in[1]);
                close(pipe_out[0]);
		
		/*Make pipes the stdin and stdout*/
                dup2(pipe_in[0], 0);
                close(pipe_in[0]);
                dup2(pipe_out[1], 1);
                close(pipe_out[1]);

		/*change a to b*/ 
                execl("/bin/tr", "tr", "a", "b" , 0);
                perror("exec prog1");
                exit(1);
    }
    else /*parent*/
    {
                /*close unneeded*/
                close(pipe_in[0]);
                close(pipe_out[1]);
                /*write to and then read from child*/
                write(pipe_in[1], "This is the data\n", 14);
                read(pipe_out[0], buffer, sizeof(buffer));

                /*send EOF to child*/
                close(pipe_in[1]);
                /*wait for end then close other end of pipe*/
                waitpid(pid, NULL, 0);
                close(pipe_out[0]);
                return EXIT_SUCCESS;
    }
}

                /*write to and then read from child*/
                write(pipe_in[1], "This is the data\n", 14);
                /*send EOF to child*/
                close(pipe_in[1]);
                read(pipe_out[0], buffer, sizeof(buffer));