1 | /* vi: set sw=4 ts=4: */
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2 | /*
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3 | * simple inotify daemon
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4 | * reports filesystem changes via userspace agent
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5 | *
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6 | * Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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7 | *
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8 | * Licensed under GPLv2, see file LICENSE in this source tree.
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9 | */
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10 |
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11 | /*
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12 | * Use as follows:
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13 | * # inotifyd /user/space/agent dir/or/file/being/watched[:mask] ...
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14 | *
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15 | * When a filesystem event matching the specified mask is occured on specified file (or directory)
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16 | * a userspace agent is spawned and given the following parameters:
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17 | * $1. actual event(s)
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18 | * $2. file (or directory) name
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19 | * $3. name of subfile (if any), in case of watching a directory
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20 | *
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21 | * E.g. inotifyd ./dev-watcher /dev:n
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22 | *
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23 | * ./dev-watcher can be, say:
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24 | * #!/bin/sh
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25 | * echo "We have new device in here! Hello, $3!"
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26 | *
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27 | * See below for mask names explanation.
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28 | */
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29 |
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30 | #include "libbb.h"
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31 | #include <sys/inotify.h>
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32 |
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33 | static const char mask_names[] ALIGN1 =
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34 | "a" // 0x00000001 File was accessed
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35 | "c" // 0x00000002 File was modified
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36 | "e" // 0x00000004 Metadata changed
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37 | "w" // 0x00000008 Writable file was closed
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38 | "0" // 0x00000010 Unwritable file closed
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39 | "r" // 0x00000020 File was opened
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40 | "m" // 0x00000040 File was moved from X
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41 | "y" // 0x00000080 File was moved to Y
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42 | "n" // 0x00000100 Subfile was created
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43 | "d" // 0x00000200 Subfile was deleted
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44 | "D" // 0x00000400 Self was deleted
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45 | "M" // 0x00000800 Self was moved
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46 | "\0" // 0x00001000 (unused)
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47 | // Kernel events, always reported:
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48 | "u" // 0x00002000 Backing fs was unmounted
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49 | "o" // 0x00004000 Event queued overflowed
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50 | "x" // 0x00008000 File is no longer watched (usually deleted)
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51 | ;
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52 | enum {
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53 | MASK_BITS = sizeof(mask_names) - 1
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54 | };
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55 |
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56 | int inotifyd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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57 | int inotifyd_main(int argc, char **argv)
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58 | {
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59 | int n;
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60 | unsigned mask;
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61 | struct pollfd pfd;
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62 | char **watches; // names of files being watched
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63 | const char *args[5];
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64 |
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65 | // sanity check: agent and at least one watch must be given
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66 | if (!argv[1] || !argv[2])
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67 | bb_show_usage();
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68 |
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69 | argv++;
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70 | // inotify_add_watch will number watched files
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71 | // starting from 1, thus watches[0] is unimportant,
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72 | // and 1st file name is watches[1].
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73 | watches = argv;
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74 | args[0] = *argv;
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75 | args[4] = NULL;
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76 | argc -= 2; // number of files we watch
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77 |
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78 | // open inotify
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79 | pfd.fd = inotify_init();
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80 | if (pfd.fd < 0)
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81 | bb_perror_msg_and_die("no kernel support");
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82 |
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83 | // setup watches
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84 | while (*++argv) {
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85 | char *path = *argv;
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86 | char *masks = strchr(path, ':');
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87 |
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88 | mask = 0x0fff; // assuming we want all non-kernel events
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89 | // if mask is specified ->
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90 | if (masks) {
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91 | *masks = '\0'; // split path and mask
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92 | // convert mask names to mask bitset
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93 | mask = 0;
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94 | while (*++masks) {
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95 | const char *found;
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96 | found = memchr(mask_names, *masks, MASK_BITS);
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97 | if (found)
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98 | mask |= (1 << (found - mask_names));
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99 | }
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100 | }
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101 | // add watch
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102 | n = inotify_add_watch(pfd.fd, path, mask);
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103 | if (n < 0)
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104 | bb_perror_msg_and_die("add watch (%s) failed", path);
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105 | //bb_error_msg("added %d [%s]:%4X", n, path, mask);
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106 | }
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107 |
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108 | // setup signals
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109 | bb_signals(BB_FATAL_SIGS, record_signo);
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110 |
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111 | // do watch
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112 | pfd.events = POLLIN;
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113 | while (1) {
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114 | int len;
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115 | void *buf;
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116 | struct inotify_event *ie;
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117 | again:
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118 | if (bb_got_signal)
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119 | break;
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120 | n = poll(&pfd, 1, -1);
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121 | // Signal interrupted us?
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122 | if (n < 0 && errno == EINTR)
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123 | goto again;
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124 | // Under Linux, above if() is not necessary.
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125 | // Non-fatal signals, e.g. SIGCHLD, when set to SIG_DFL,
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126 | // are not interrupting poll().
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127 | // Thus we can just break if n <= 0 (see below),
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128 | // because EINTR will happen only on SIGTERM et al.
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129 | // But this might be not true under other Unixes,
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130 | // and is generally way too subtle to depend on.
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131 | if (n <= 0) // strange error?
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132 | break;
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133 |
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134 | // read out all pending events
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135 | // (NB: len must be int, not ssize_t or long!)
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136 | xioctl(pfd.fd, FIONREAD, &len);
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137 | #define eventbuf bb_common_bufsiz1
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138 | ie = buf = (len <= sizeof(eventbuf)) ? eventbuf : xmalloc(len);
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139 | len = full_read(pfd.fd, buf, len);
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140 | // process events. N.B. events may vary in length
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141 | while (len > 0) {
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142 | int i;
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143 | // cache relevant events mask
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144 | unsigned m = ie->mask & ((1 << MASK_BITS) - 1);
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145 | if (m) {
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146 | char events[MASK_BITS + 1];
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147 | char *s = events;
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148 | for (i = 0; i < MASK_BITS; ++i, m >>= 1) {
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149 | if ((m & 1) && (mask_names[i] != '\0'))
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150 | *s++ = mask_names[i];
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151 | }
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152 | *s = '\0';
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153 | // bb_error_msg("exec %s %08X\t%s\t%s\t%s", args[0],
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154 | // ie->mask, events, watches[ie->wd], ie->len ? ie->name : "");
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155 | args[1] = events;
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156 | args[2] = watches[ie->wd];
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157 | args[3] = ie->len ? ie->name : NULL;
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158 | spawn_and_wait((char **)args);
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159 | // we are done if all files got final x event
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160 | if (ie->mask & 0x8000) {
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161 | if (--argc <= 0)
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162 | goto done;
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163 | inotify_rm_watch(pfd.fd, ie->wd);
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164 | }
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165 | }
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166 | // next event
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167 | i = sizeof(struct inotify_event) + ie->len;
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168 | len -= i;
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169 | ie = (void*)((char*)ie + i);
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170 | }
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171 | if (eventbuf != buf)
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172 | free(buf);
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173 | } // while (1)
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174 | done:
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175 | return bb_got_signal;
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176 | }
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