#include "apue.h"voiddo_driver(char *driver){	pid_t	child;	int		pipe[2];	/*	 * Create a stream pipe to communicate with the driver.	 */	if (s_pipe(pipe) < 0)		err_sys("can't create stream pipe");	if ((child = fork()) < 0) {		err_sys("fork error");	} else if (child == 0) {		/* child */		close(pipe[1]);		/* stdin for driver */		if (dup2(pipe[0], STDIN_FILENO) != STDIN_FILENO)			err_sys("dup2 error to stdin");		/* stdout for driver */		if (dup2(pipe[0], STDOUT_FILENO) != STDOUT_FILENO)			err_sys("dup2 error to stdout");		if (pipe[0] != STDIN_FILENO && pipe[0] != STDOUT_FILENO)			close(pipe[0]);		/* leave stderr for driver alone */		execlp(driver, driver, (char *)0);		err_sys("execlp error for: %s", driver);	}	close(pipe[0]);		/* parent */	if (dup2(pipe[1], STDIN_FILENO) != STDIN_FILENO)		err_sys("dup2 error to stdin");	if (dup2(pipe[1], STDOUT_FILENO) != STDOUT_FILENO)		err_sys("dup2 error to stdout");	if (pipe[1] != STDIN_FILENO && pipe[1] != STDOUT_FILENO)		close(pipe[1]);	/*	 * Parent returns, but with stdin and stdout connected	 * to the driver.	 */}