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/* vi: set sw=4 ts=4: */
/*
* simple inotify daemon
* reports filesystem changes via userspace agent
*
* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
*
* Licensed under GPLv2, see file LICENSE in this tarball for details.
*/
/*
* Use as follows:
* # inotifyd /user/space/agent dir/or/file/being/watched[:mask] ...
*
* When a filesystem event matching the specified mask is occured on specified file (or directory)
* a userspace agent is spawned and given the following parameters:
* $1. actual event(s)
* $2. file (or directory) name
* $3. name of subfile (if any), in case of watching a directory
*
* E.g. inotifyd ./dev-watcher /dev:n
*
* ./dev-watcher can be, say:
* #!/bin/sh
* echo "We have new device in here! Hello, $3!"
*
* See below for mask names explanation.
*/
#include "libbb.h"
#include <sys/inotify.h>
static const char mask_names[] ALIGN1 =
"a" // 0x00000001 File was accessed
"c" // 0x00000002 File was modified
"e" // 0x00000004 Metadata changed
"w" // 0x00000008 Writable file was closed
"0" // 0x00000010 Unwritable file closed
"r" // 0x00000020 File was opened
"m" // 0x00000040 File was moved from X
"y" // 0x00000080 File was moved to Y
"n" // 0x00000100 Subfile was created
"d" // 0x00000200 Subfile was deleted
"D" // 0x00000400 Self was deleted
"M" // 0x00000800 Self was moved
"\0" // 0x00001000 (unused)
// Kernel events, always reported:
"u" // 0x00002000 Backing fs was unmounted
"o" // 0x00004000 Event queued overflowed
"x" // 0x00008000 File is no longer watched (usually deleted)
;
enum {
MASK_BITS = sizeof(mask_names) - 1
};
int inotifyd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
int inotifyd_main(int argc, char **argv)
{
int n;
unsigned mask;
struct pollfd pfd;
char **watches; // names of files being watched
const char *args[5];
// sanity check: agent and at least one watch must be given
if (!argv[1] || !argv[2])
bb_show_usage();
argv++;
// inotify_add_watch will number watched files
// starting from 1, thus watches[0] is unimportant,
// and 1st file name is watches[1].
watches = argv;
args[0] = *argv;
args[4] = NULL;
argc -= 2; // number of files we watch
// open inotify
pfd.fd = inotify_init();
if (pfd.fd < 0)
bb_perror_msg_and_die("no kernel support");
// setup watches
while (*++argv) {
char *path = *argv;
char *masks = strchr(path, ':');
mask = 0x0fff; // assuming we want all non-kernel events
// if mask is specified ->
if (masks) {
*masks = '\0'; // split path and mask
// convert mask names to mask bitset
mask = 0;
while (*++masks) {
const char *found;
found = memchr(mask_names, *masks, MASK_BITS);
if (found)
mask |= (1 << (found - mask_names));
}
}
// add watch
n = inotify_add_watch(pfd.fd, path, mask);
if (n < 0)
bb_perror_msg_and_die("add watch (%s) failed", path);
//bb_error_msg("added %d [%s]:%4X", n, path, mask);
}
// setup signals
bb_signals(BB_FATAL_SIGS, record_signo);
// do watch
pfd.events = POLLIN;
while (1) {
int len;
void *buf;
struct inotify_event *ie;
again:
if (bb_got_signal)
break;
n = poll(&pfd, 1, -1);
// Signal interrupted us?
if (n < 0 && errno == EINTR)
goto again;
// Under Linux, above if() is not necessary.
// Non-fatal signals, e.g. SIGCHLD, when set to SIG_DFL,
// are not interrupting poll().
// Thus we can just break if n <= 0 (see below),
// because EINTR will happen only on SIGTERM et al.
// But this might be not true under other Unixes,
// and is generally way too subtle to depend on.
if (n <= 0) // strange error?
break;
// read out all pending events
// (NB: len must be int, not ssize_t or long!)
xioctl(pfd.fd, FIONREAD, &len);
#define eventbuf bb_common_bufsiz1
ie = buf = (len <= sizeof(eventbuf)) ? eventbuf : xmalloc(len);
len = full_read(pfd.fd, buf, len);
// process events. N.B. events may vary in length
while (len > 0) {
int i;
// cache relevant events mask
unsigned m = ie->mask & ((1 << MASK_BITS) - 1);
if (m) {
char events[MASK_BITS + 1];
char *s = events;
for (i = 0; i < MASK_BITS; ++i, m >>= 1) {
if ((m & 1) && (mask_names[i] != '\0'))
*s++ = mask_names[i];
}
*s = '\0';
// bb_error_msg("exec %s %08X\t%s\t%s\t%s", args[0],
// ie->mask, events, watches[ie->wd], ie->len ? ie->name : "");
args[1] = events;
args[2] = watches[ie->wd];
args[3] = ie->len ? ie->name : NULL;
wait4pid(xspawn((char **)args));
// we are done if all files got final x event
if (ie->mask & 0x8000) {
if (--argc <= 0)
goto done;
inotify_rm_watch(pfd.fd, ie->wd);
}
}
// next event
i = sizeof(struct inotify_event) + ie->len;
len -= i;
ie = (void*)((char*)ie + i);
}
if (eventbuf != buf)
free(buf);
} // while (1)
done:
return bb_got_signal;
}
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