fig19.17

UNIX环境高级编程书的源代码

#include "apue.h"

void
do_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.
	 */
}