1 | /*
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2 | * devno.c - find a particular device by its device number (major/minor)
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3 | *
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4 | * Copyright (C) 2000, 2001, 2003 Theodore Ts'o
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5 | * Copyright (C) 2001 Andreas Dilger
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6 | *
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7 | * %Begin-Header%
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8 | * This file may be redistributed under the terms of the
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9 | * GNU Lesser General Public License.
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10 | * %End-Header%
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11 | */
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12 |
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13 | #include <stdio.h>
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14 | #include <string.h>
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15 | #if HAVE_UNISTD_H
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16 | #include <unistd.h>
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17 | #endif
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18 | #include <stdlib.h>
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19 | #include <string.h>
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20 | #if HAVE_SYS_TYPES_H
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21 | #include <sys/types.h>
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22 | #endif
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23 | #if HAVE_SYS_STAT_H
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24 | #include <sys/stat.h>
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25 | #endif
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26 | #include <dirent.h>
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27 | #if HAVE_ERRNO_H
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28 | #include <errno.h>
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29 | #endif
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30 | #if HAVE_SYS_MKDEV_H
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31 | #include <sys/mkdev.h>
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32 | #endif
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33 |
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34 | #include "blkidP.h"
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35 |
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36 | struct dir_list {
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37 | char *name;
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38 | struct dir_list *next;
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39 | };
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40 |
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41 | char *blkid_strndup(const char *s, int length)
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42 | {
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43 | char *ret;
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44 |
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45 | if (!s)
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46 | return NULL;
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47 |
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48 | if (!length)
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49 | length = strlen(s);
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50 |
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51 | ret = xmalloc(length + 1);
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52 | strncpy(ret, s, length);
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53 | ret[length] = '\0';
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54 | return ret;
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55 | }
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56 |
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57 | char *blkid_strdup(const char *s)
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58 | {
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59 | return blkid_strndup(s, 0);
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60 | }
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61 |
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62 | /*
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63 | * This function adds an entry to the directory list
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64 | */
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65 | static void add_to_dirlist(const char *name, struct dir_list **list)
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66 | {
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67 | struct dir_list *dp;
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68 |
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69 | dp = xmalloc(sizeof(struct dir_list));
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70 | dp->name = blkid_strdup(name);
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71 | dp->next = *list;
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72 | *list = dp;
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73 | }
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74 |
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75 | /*
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76 | * This function frees a directory list
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77 | */
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78 | static void free_dirlist(struct dir_list **list)
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79 | {
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80 | struct dir_list *dp, *next;
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81 |
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82 | for (dp = *list; dp; dp = next) {
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83 | next = dp->next;
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84 | free(dp->name);
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85 | free(dp);
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86 | }
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87 | *list = NULL;
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88 | }
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89 |
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90 | static void scan_dir(char *dir_name, dev_t devno, struct dir_list **list,
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91 | char **devname)
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92 | {
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93 | DIR *dir;
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94 | struct dirent *dp;
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95 | char path[1024];
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96 | int dirlen;
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97 | struct stat st;
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98 |
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99 | if ((dir = opendir(dir_name)) == NULL)
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100 | return;
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101 | dirlen = strlen(dir_name) + 2;
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102 | while ((dp = readdir(dir)) != 0) {
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103 | if (dirlen + strlen(dp->d_name) >= sizeof(path))
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104 | continue;
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105 |
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106 | if (dp->d_name[0] == '.' &&
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107 | ((dp->d_name[1] == 0) ||
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108 | ((dp->d_name[1] == '.') && (dp->d_name[2] == 0))))
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109 | continue;
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110 |
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111 | sprintf(path, "%s/%s", dir_name, dp->d_name);
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112 | if (stat(path, &st) < 0)
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113 | continue;
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114 |
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115 | if (S_ISDIR(st.st_mode))
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116 | add_to_dirlist(path, list);
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117 | else if (S_ISBLK(st.st_mode) && st.st_rdev == devno) {
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118 | *devname = blkid_strdup(path);
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119 | DBG(DEBUG_DEVNO,
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120 | printf("found 0x%llx at %s (%p)\n", devno,
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121 | path, *devname));
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122 | break;
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123 | }
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124 | }
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125 | closedir(dir);
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126 | return;
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127 | }
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128 |
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129 | /* Directories where we will try to search for device numbers */
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130 | const char *blkid_devdirs[] = { "/devices", "/devfs", "/dev", NULL };
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131 |
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132 | /*
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133 | * This function finds the pathname to a block device with a given
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134 | * device number. It returns a pointer to allocated memory to the
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135 | * pathname on success, and NULL on failure.
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136 | */
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137 | char *blkid_devno_to_devname(dev_t devno)
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138 | {
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139 | struct dir_list *list = NULL, *new_list = NULL;
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140 | char *devname = NULL;
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141 | const char **dir;
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142 |
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143 | /*
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144 | * Add the starting directories to search in reverse order of
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145 | * importance, since we are using a stack...
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146 | */
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147 | for (dir = blkid_devdirs; *dir; dir++)
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148 | add_to_dirlist(*dir, &list);
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149 |
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150 | while (list) {
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151 | struct dir_list *current = list;
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152 |
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153 | list = list->next;
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154 | DBG(DEBUG_DEVNO, printf("directory %s\n", current->name));
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155 | scan_dir(current->name, devno, &new_list, &devname);
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156 | free(current->name);
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157 | free(current);
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158 | if (devname)
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159 | break;
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160 | /*
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161 | * If we're done checking at this level, descend to
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162 | * the next level of subdirectories. (breadth-first)
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163 | */
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164 | if (list == NULL) {
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165 | list = new_list;
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166 | new_list = NULL;
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167 | }
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168 | }
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169 | free_dirlist(&list);
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170 | free_dirlist(&new_list);
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171 |
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172 | if (!devname) {
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173 | DBG(DEBUG_DEVNO,
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174 | printf("blkid: couldn't find devno 0x%04lx\n",
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175 | (unsigned long) devno));
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176 | } else {
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177 | DBG(DEBUG_DEVNO,
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178 | printf("found devno 0x%04llx as %s\n", devno, devname));
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179 | }
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180 |
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181 |
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182 | return devname;
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183 | }
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184 |
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185 | #ifdef TEST_PROGRAM
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186 | int main(int argc, char** argv)
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187 | {
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188 | char *devname, *tmp;
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189 | int major, minor;
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190 | dev_t devno;
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191 | const char *errmsg = "Couldn't parse %s: %s\n";
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192 |
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193 | blkid_debug_mask = DEBUG_ALL;
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194 | if ((argc != 2) && (argc != 3)) {
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195 | fprintf(stderr, "Usage:\t%s device_number\n\t%s major minor\n"
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196 | "Resolve a device number to a device name\n",
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197 | argv[0], argv[0]);
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198 | exit(1);
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199 | }
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200 | if (argc == 2) {
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201 | devno = strtoul(argv[1], &tmp, 0);
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202 | if (*tmp) {
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203 | fprintf(stderr, errmsg, "device number", argv[1]);
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204 | exit(1);
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205 | }
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206 | } else {
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207 | major = strtoul(argv[1], &tmp, 0);
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208 | if (*tmp) {
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209 | fprintf(stderr, errmsg, "major number", argv[1]);
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210 | exit(1);
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211 | }
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212 | minor = strtoul(argv[2], &tmp, 0);
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213 | if (*tmp) {
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214 | fprintf(stderr, errmsg, "minor number", argv[2]);
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215 | exit(1);
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216 | }
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217 | devno = makedev(major, minor);
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218 | }
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219 | printf("Looking for device 0x%04Lx\n", devno);
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220 | devname = blkid_devno_to_devname(devno);
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221 | free(devname);
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222 | return 0;
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223 | }
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224 | #endif
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