225 lines
6.5 KiB
C
225 lines
6.5 KiB
C
/* vi: set sw=4 ts=4: */
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/*
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* simple inotify daemon
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* reports filesystem changes via userspace agent
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*
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* Copyright (C) 2008 by Vladimir Dronnikov <dronnikov@gmail.com>
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*
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* Licensed under GPLv2, see file LICENSE in this source tree.
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*/
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/*
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* Use as follows:
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* # inotifyd /user/space/agent dir/or/file/being/watched[:mask] ...
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*
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* When a filesystem event matching the specified mask is occurred on specified file (or directory)
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* a userspace agent is spawned and given the following parameters:
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* $1. actual event(s)
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* $2. file (or directory) name
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* $3. name of subfile (if any), in case of watching a directory
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*
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* E.g. inotifyd ./dev-watcher /dev:n
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*
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* ./dev-watcher can be, say:
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* #!/bin/sh
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* echo "We have new device in here! Hello, $3!"
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*
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* See below for mask names explanation.
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*/
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//config:config INOTIFYD
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//config: bool "inotifyd (3.6 kb)"
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//config: default n # doesn't build on Knoppix 5
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//config: help
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//config: Simple inotify daemon. Reports filesystem changes. Requires
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//config: kernel >= 2.6.13
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//applet:IF_INOTIFYD(APPLET(inotifyd, BB_DIR_SBIN, BB_SUID_DROP))
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//kbuild:lib-$(CONFIG_INOTIFYD) += inotifyd.o
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//usage:#define inotifyd_trivial_usage
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//usage: "PROG FILE1[:MASK]..."
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//usage:#define inotifyd_full_usage "\n\n"
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//usage: "Run PROG on filesystem changes."
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//usage: "\nWhen a filesystem event matching MASK occurs on FILEn,"
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//usage: "\nPROG ACTUAL_EVENTS FILEn [SUBFILE] is run."
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//usage: "\nIf PROG is -, events are sent to stdout."
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//usage: "\nEvents:"
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//usage: "\n a File is accessed"
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//usage: "\n c File is modified"
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//usage: "\n e Metadata changed"
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//usage: "\n w Writable file is closed"
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//usage: "\n 0 Unwritable file is closed"
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//usage: "\n r File is opened"
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//usage: "\n D File is deleted"
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//usage: "\n M File is moved"
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//usage: "\n u Backing fs is unmounted"
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//usage: "\n o Event queue overflowed"
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//usage: "\n x File can't be watched anymore"
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//usage: "\nIf watching a directory:"
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//usage: "\n y Subfile is moved into dir"
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//usage: "\n m Subfile is moved out of dir"
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//usage: "\n n Subfile is created"
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//usage: "\n d Subfile is deleted"
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//usage: "\n"
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//usage: "\ninotifyd waits for PROG to exit."
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//usage: "\nWhen x event happens for all FILEs, inotifyd exits."
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#include "libbb.h"
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#include "common_bufsiz.h"
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#include <sys/inotify.h>
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static const char mask_names[] ALIGN1 =
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"a" // 0x00000001 File was accessed
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"c" // 0x00000002 File was modified
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"e" // 0x00000004 Metadata changed
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"w" // 0x00000008 Writable file was closed
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"0" // 0x00000010 Unwritable file closed
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"r" // 0x00000020 File was opened
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"m" // 0x00000040 File was moved from X
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"y" // 0x00000080 File was moved to Y
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"n" // 0x00000100 Subfile was created
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"d" // 0x00000200 Subfile was deleted
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"D" // 0x00000400 Self was deleted
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"M" // 0x00000800 Self was moved
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"\0" // 0x00001000 (unused)
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// Kernel events, always reported:
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"u" // 0x00002000 Backing fs was unmounted
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"o" // 0x00004000 Event queued overflowed
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"x" // 0x00008000 File is no longer watched (usually deleted)
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;
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enum {
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MASK_BITS = sizeof(mask_names) - 1
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};
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int inotifyd_main(int argc, char **argv) MAIN_EXTERNALLY_VISIBLE;
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int inotifyd_main(int argc, char **argv)
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{
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int n;
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unsigned mask;
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struct pollfd pfd;
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char **watches; // names of files being watched
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const char *args[5];
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// sanity check: agent and at least one watch must be given
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if (!argv[1] || !argv[2])
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bb_show_usage();
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argv++;
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// inotify_add_watch will number watched files
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// starting from 1, thus watches[0] is unimportant,
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// and 1st file name is watches[1].
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watches = argv;
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args[0] = *argv;
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args[4] = NULL;
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argc -= 2; // number of files we watch
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// open inotify
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pfd.fd = inotify_init();
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if (pfd.fd < 0)
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bb_perror_msg_and_die("no kernel support");
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// setup watches
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while (*++argv) {
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char *path = *argv;
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char *masks = strchr(path, ':');
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mask = 0x0fff; // assuming we want all non-kernel events
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// if mask is specified ->
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if (masks) {
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*masks = '\0'; // split path and mask
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// convert mask names to mask bitset
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mask = 0;
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while (*++masks) {
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const char *found;
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found = memchr(mask_names, *masks, MASK_BITS);
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if (found)
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mask |= (1 << (found - mask_names));
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}
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}
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// add watch
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n = inotify_add_watch(pfd.fd, path, mask);
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if (n < 0)
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bb_perror_msg_and_die("add watch (%s) failed", path);
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//bb_error_msg("added %d [%s]:%4X", n, path, mask);
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}
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// setup signals
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bb_signals(BB_FATAL_SIGS, record_signo);
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// do watch
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pfd.events = POLLIN;
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while (1) {
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int len;
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void *buf;
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struct inotify_event *ie;
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again:
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if (bb_got_signal)
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break;
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n = poll(&pfd, 1, -1);
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// Signal interrupted us?
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if (n < 0 && errno == EINTR)
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goto again;
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// Under Linux, above if() is not necessary.
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// Non-fatal signals, e.g. SIGCHLD, when set to SIG_DFL,
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// are not interrupting poll().
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// Thus we can just break if n <= 0 (see below),
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// because EINTR will happen only on SIGTERM et al.
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// But this might be not true under other Unixes,
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// and is generally way too subtle to depend on.
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if (n <= 0) // strange error?
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break;
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// read out all pending events
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// (NB: len must be int, not ssize_t or long!)
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#define eventbuf bb_common_bufsiz1
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setup_common_bufsiz();
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xioctl(pfd.fd, FIONREAD, &len);
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ie = buf = (len <= COMMON_BUFSIZE) ? eventbuf : xmalloc(len);
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len = full_read(pfd.fd, buf, len);
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// process events. N.B. events may vary in length
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while (len > 0) {
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int i;
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// cache relevant events mask
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unsigned m = ie->mask & ((1 << MASK_BITS) - 1);
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if (m) {
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char events[MASK_BITS + 1];
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char *s = events;
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for (i = 0; i < MASK_BITS; ++i, m >>= 1) {
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if ((m & 1) && (mask_names[i] != '\0'))
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*s++ = mask_names[i];
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}
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*s = '\0';
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if (LONE_CHAR(args[0], '-')) {
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/* "inotifyd - FILE": built-in echo */
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printf(ie->len ? "%s\t%s\t%s\n" : "%s\t%s\n", events,
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watches[ie->wd],
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ie->name);
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fflush(stdout);
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} else {
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// bb_error_msg("exec %s %08X\t%s\t%s\t%s", args[0],
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// ie->mask, events, watches[ie->wd], ie->len ? ie->name : "");
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args[1] = events;
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args[2] = watches[ie->wd];
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args[3] = ie->len ? ie->name : NULL;
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spawn_and_wait((char **)args);
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}
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// we are done if all files got final x event
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if (ie->mask & 0x8000) {
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if (--argc <= 0)
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goto done;
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inotify_rm_watch(pfd.fd, ie->wd);
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}
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}
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// next event
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i = sizeof(struct inotify_event) + ie->len;
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len -= i;
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ie = (void*)((char*)ie + i);
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}
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if (eventbuf != buf)
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free(buf);
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} // while (1)
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done:
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return bb_got_signal;
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}
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