misc/e2label.c

   1 /*
   2  * e2label.c            - Print or change the volume label on an ext2 fs
   3  *
   4  * Written by Andries Brouwer (aeb@cwi.nl), 970714
   5  *
   6  * Copyright 1997, 1998 by Theodore Ts'o.
   7  *
   8  * %Begin-Header%
   9  * This file may be redistributed under the terms of the GNU Public
  10  * License.
  11  * %End-Header%
  12  */
  13
  14 #include "config.h"
  15 #include <stdio.h>
  16 #include <string.h>
  17 #include <fcntl.h>
  18 #include <ctype.h>
  19 #include <termios.h>
  20 #include <time.h>
  21 #ifdef HAVE_GETOPT_H
  22 #include <getopt.h>
  23 #else
  24 extern char *optarg;
  25 extern int optind;
  26 #endif
  27 #ifdef HAVE_UNISTD_H
  28 #include <unistd.h>
  29 #endif
  30 #ifdef HAVE_STDLIB_H
  31 #include <stdlib.h>
  32 #endif
  33 #ifdef HAVE_ERRNO_H
  34 #include <errno.h>
  35 #endif
  36 #include "support/nls-enable.h"
  37
  38 #define EXT2_SUPER_MAGIC 0xEF53
  39
  40 #define VOLNAMSZ 16
  41
  42 struct ext2_super_block {
  43         char  s_dummy0[56];
  44         unsigned char  s_magic[2];
  45         char  s_dummy1[62];
  46         char  s_volume_name[VOLNAMSZ];
  47         char  s_last_mounted[64];
  48         char  s_dummy2[824];
  49 } sb;
  50
  51 static int open_e2fs (char *dev, int mode)
  52 {
  53         int fd;
  54
  55         fd = open(dev, mode);
  56         if (fd < 0) {
  57              perror(dev);
  58              fprintf (stderr, _("e2label: cannot open %s\n"), dev);
  59              exit(1);
  60         }
  61         if (lseek(fd, 1024, SEEK_SET) != 1024) {
  62              perror(dev);
  63              fprintf (stderr, _("e2label: cannot seek to superblock\n"));
  64              exit(1);
  65         }
  66         if (read(fd, (char *) &sb, sizeof(sb)) != sizeof(sb)) {
  67              perror(dev);
  68              fprintf (stderr, _("e2label: error reading superblock\n"));
  69              exit(1);
  70         }
  71         if (sb.s_magic[0] + 256*sb.s_magic[1] != EXT2_SUPER_MAGIC) {
  72              fprintf (stderr, _("e2label: not an ext2 filesystem\n"));
  73              exit(1);
  74         }
  75
  76         return fd;
  77 }
  78
  79 static void print_label (char *dev)
  80 {
  81         char label[VOLNAMSZ+1];
  82
  83         open_e2fs (dev, O_RDONLY);
  84         strncpy(label, sb.s_volume_name, VOLNAMSZ);
  85         label[VOLNAMSZ] = 0;
  86         printf("%s\n", label);
  87 }
  88
  89 static void change_label (char *dev, char *label)
  90 {
  91         int fd;
  92
  93         fd = open_e2fs(dev, O_RDWR);
  94         memset(sb.s_volume_name, 0, VOLNAMSZ);
  95         strncpy(sb.s_volume_name, label, VOLNAMSZ);
  96         if (strlen(label) > VOLNAMSZ)
  97                 fprintf(stderr, _("Warning: label too long, truncating.\n"));
  98         if (lseek(fd, 1024, SEEK_SET) != 1024) {
  99              perror(dev);
 100              fprintf (stderr, _("e2label: cannot seek to superblock again\n"));
 101              exit(1);
 102         }
 103         if (write(fd, (char *) &sb, sizeof(sb)) != sizeof(sb)) {
 104              perror(dev);
 105              fprintf (stderr, _("e2label: error writing superblock\n"));
 106              exit(1);
 107         }
 108 }
 109
 110 int main (int argc, char ** argv)
 111 {
 112         if (argc == 2)
 113              print_label(argv[1]);
 114         else if (argc == 3)
 115              change_label(argv[1], argv[2]);
 116         else {
 117              fprintf(stderr, _("Usage: e2label device [newlabel]\n"));
 118              exit(1);
 119         }
 120         return 0;
 121 }