open.c

该代码为unix环境高级编程的源代码

#include	"open.h"
#include	<sys/uio.h>		/* struct iovec */

/* Open the file by sending the "name" and "oflag" to the
 * connection server and reading a file descriptor back. */

int
csopen(char *name, int oflag)
{
	pid_t			pid;
	int				len;
	char			buf[10];
	struct iovec	iov[3];
	static int		fd[2] = { -1, -1 };

	if (fd[0] < 0) {	/* fork/exec our open server first time */
		if (s_pipe(fd) < 0)
			err_sys("s_pipe error");
		if ( (pid = fork()) < 0)
			err_sys("fork error");
		else if (pid == 0) {		/* child */
			close(fd[0]);
			if (fd[1] != STDIN_FILENO) {
				if (dup2(fd[1], STDIN_FILENO) != STDIN_FILENO)
					err_sys("dup2 error to stdin");
			}
			if (fd[1] != STDOUT_FILENO) {
				if (dup2(fd[1], STDOUT_FILENO) != STDOUT_FILENO)
					err_sys("dup2 error to stdout");
			}
			if (execl("./opend", "opend", NULL) < 0)
				err_sys("execl error");
		}
		close(fd[1]);				/* parent */
	}

	sprintf(buf, " %d", oflag);		/* oflag to ascii */
	iov[0].iov_base = CL_OPEN " ";
	iov[0].iov_len  = strlen(CL_OPEN) + 1;
	iov[1].iov_base = name;
	iov[1].iov_len  = strlen(name);
	iov[2].iov_base = buf;
	iov[2].iov_len  = strlen(buf) + 1;	/* +1 for null at end of buf */
	len = iov[0].iov_len + iov[1].iov_len + iov[2].iov_len;
	if (writev(fd[0], &iov[0], 3) != len)
		err_sys("writev error");

			/* read descriptor, returned errors handled by write() */
	return( recv_fd(fd[0], write) );
}