#include <err.h>#include <stdlib.h>#include <stdio.h>#include <unistd.h> #include <sys/stat.h>#include <sys/mount.h> intmain(int argc, char **argv){	char *old = NULL, *new = NULL;	struct stat stbuf; 	while (*++argv) {		if (!old) {			old = *argv;		} else if (!new) {			new = *argv;		} else {			errx(1, "%s: too many arguments", *argv);		}	} 	if (!old || !new) {		errx(1, "usage: 9bind old new");	} 	/* Make sure mount exists, is writable, and not sticky */	if (stat(new, &stbuf) || access(new, W_OK)) {		err(1, "%s", new);	}	if (stbuf.st_mode & S_ISVTX) {		errx(1, "%s: refusing to bind over sticky directory", new);	} 	if (mount(old, new, NULL, MS_BIND, NULL)) {		err(1, "mount");	} 	return 0;}