/* printroot - print root device on stdout	Author: Bruce Evans *//* This program figures out what the root device is by doing a stat on it, and * then searching /dev until it finds an entry with the same device number. * A typical use (probably the only use) is in /etc/rc for initializing * /etc/mtab, as follows: * *	/usr/bin/printroot >/etc/mtab * *  9 Dec 1989	- clean up for 1.5 - full prototypes (BDE) * 15 Oct 1989	- avoid ACK cc bugs (BDE): *		- sizeof "foo" is 2 (from wrong type char *) instead of 4 *		- char foo[10] = "bar"; allocates 4 bytes instead of 10 *  1 Oct 1989	- Minor changes by Andy Tanenbaum *  5 Oct 1992	- Use readdir (kjb) * 26 Nov 1994	- Flag -r: print just the root device (kjb) */#include <sys/types.h>#include <sys/stat.h>#include <fcntl.h>#include <limits.h>#include <stdlib.h>#include <string.h>#include <unistd.h>#include <minix/minlib.h>#include <dirent.h>static char DEV_PATH[] = "/dev/";	/* #define would step on sizeof bug */static char MESSAGE[] = " / ";	/* ditto */#define UNKNOWN_DEV	"/dev/unknown"#define ROOT		"/"int rflag;_PROTOTYPE(int main, (int argc, char **argv));_PROTOTYPE(void done, (char *name, int status));int main(argc, argv)int argc;char **argv;{  DIR *dp;  struct dirent *entry;  struct stat filestat, rootstat;  static char namebuf[sizeof DEV_PATH + NAME_MAX];  rflag = (argc > 1 && strcmp(argv[1], "-r") == 0);  if (stat(ROOT, &rootstat) == 0 && (dp = opendir(DEV_PATH)) != (DIR *) NULL) {	while ((entry = readdir(dp)) != (struct dirent *) NULL) {		strcpy(namebuf, DEV_PATH);		strcat(namebuf, entry->d_name);		if (stat(namebuf, &filestat) != 0) continue;		if ((filestat.st_mode & S_IFMT) != S_IFBLK) continue;		if (filestat.st_rdev != rootstat.st_dev) continue;		done(namebuf, 0);	}  }  done(UNKNOWN_DEV, 1);  return(0);			/* not reached */}void done(name, status)char *name;int status;{  int v;  write(1, name, strlen(name));  if (rflag) {	write(1, "\n", 1);	exit(status);  }  write(1, MESSAGE, sizeof MESSAGE - 1);  v = fsversion(name, "printroot");	/* determine file system version */  if (v == 1)	write(1, "1 rw\n", 5);  else if (v == 2)	write(1, "2 rw\n", 5);  else	write(1, "0 rw\n", 5);  exit(status);}