commands/simple/printroot.c

   1 /* printroot - print root device on stdout      Author: Bruce Evans */
   2
   3 /* This program figures out what the root device is by doing a stat on it, and
   4  * then searching /dev until it finds an entry with the same device number.
   5  * A typical use (probably the only use) is in /etc/rc for initializing
   6  * /etc/mtab, as follows:
   7  *
   8  *      /usr/bin/printroot >/etc/mtab
   9  *
  10  *  9 Dec 1989  - clean up for 1.5 - full prototypes (BDE)
  11  * 15 Oct 1989  - avoid ACK cc bugs (BDE):
  12  *              - sizeof "foo" is 2 (from wrong type char *) instead of 4
  13  *              - char foo[10] = "bar"; allocates 4 bytes instead of 10
  14  *  1 Oct 1989  - Minor changes by Andy Tanenbaum
  15  *  5 Oct 1992  - Use readdir (kjb)
  16  * 26 Nov 1994  - Flag -r: print just the root device (kjb)
  17  */
  18
  19 #include <sys/types.h>
  20 #include <sys/stat.h>
  21 #include <fcntl.h>
  22 #include <limits.h>
  23 #include <stdlib.h>
  24 #include <string.h>
  25 #include <unistd.h>
  26 #include <minix/minlib.h>
  27 #include <dirent.h>
  28
  29 static char DEV_PATH[] = "/dev/";       /* #define would step on sizeof bug */
  30 static char MESSAGE[] = " / ";  /* ditto */
  31 #define UNKNOWN_DEV     "/dev/unknown"
  32 #define ROOT            "/"
  33 int rflag;
  34
  35 _PROTOTYPE(int main, (int argc, char **argv));
  36 _PROTOTYPE(void done, (char *name, int status));
  37
  38 int main(argc, argv)
  39 int argc;
  40 char **argv;
  41 {
  42   DIR *dp;
  43   struct dirent *entry;
  44   struct stat filestat, rootstat;
  45   static char namebuf[sizeof DEV_PATH + NAME_MAX];
  46
  47   rflag = (argc > 1 && strcmp(argv[1], "-r") == 0);
  48
  49   if (stat(ROOT, &rootstat) == 0 && (dp = opendir(DEV_PATH)) != (DIR *) NULL) {
  50         while ((entry = readdir(dp)) != (struct dirent *) NULL) {
  51                 strcpy(namebuf, DEV_PATH);
  52                 strcat(namebuf, entry->d_name);
  53                 if (stat(namebuf, &filestat) != 0) continue;
  54                 if ((filestat.st_mode & S_IFMT) != S_IFBLK) continue;
  55                 if (filestat.st_rdev != rootstat.st_dev) continue;
  56                 done(namebuf, 0);
  57         }
  58   }
  59   done(UNKNOWN_DEV, 1);
  60   return(0);                    /* not reached */
  61 }
  62
  63 void done(name, status)
  64 char *name;
  65 int status;
  66 {
  67   int v;
  68
  69   write(1, name, strlen(name));
  70   if (rflag) {
  71         write(1, "\n", 1);
  72         exit(status);
  73   }
  74   write(1, MESSAGE, sizeof MESSAGE - 1);
  75   v = fsversion(name, "printroot");     /* determine file system version */
  76   if (v == 1)
  77         write(1, "1 rw\n", 5);
  78   else if (v == 2)
  79         write(1, "2 rw\n", 5);
  80   else if (v == 3)
  81         write(1, "3 rw\n", 5);
  82   else
  83         write(1, "0 rw\n", 5);
  84   exit(status);
  85 }