文章整理自：http://ixdba.blog.51cto.com/2895551/580280
前面我们已经讲解了如何使用rsync实现文件同步，但是rsync会存在一些缺点：
NAMEinotifywait - wait for changes to files using inotify
SYNOPSIS
inotifywait [-hcmrq] [-e <event> ] [-t <seconds> ] [--format <fmt> ] [--timefmt <fmt> ] <file> [ ... ]
DESCRIPTION
inotifywait efficiently waits for changes to files using Linux?. inotify(7) interface. It is suitable
for waiting for changes to files from shell scripts. It can either exit once an event occurs, or con-
tinually execute and output events as they occur.
OUTPUT
inotifywait will output diagnostic information on standard error and event information on standard
output. The event output can be configured, but by default it consists of lines of the following
form:
watched_filename EVENT_NAMES event_filename
watched_filename
is the name of the file on which the event occurred. If the file is a directory, a trailing
slash is output.
EVENT_NAMES
are the names of the inotify events which occurred, separated by commas.
event_filename
is output only when the event occurred on a directory, and in this case the name of the file
within the directory which caused this event is output.
By default, any special characters in filenames are not escaped in any way. This can make the
output of inotifywait difficult to parse in awk scripts or similar. The --csv and --format
options will be helpful in this case.
OPTIONS
-h, --help
Output some helpful usage information.
@<file>
When watching a directory tree recursively, exclude the specified file from being watched. The
file must be specified with a relative or absolute path according to whether a relative or
absolute path is given for watched directories. If a specific path is explicitly both included
and excluded, it will always be watched.
Note: If you need to watch a directory or file whose name starts with @, give the absolute
path.
--fromfile <file>
Read filenames to watch or exclude from a file, one filename per line. If filenames begin with
@ they are excluded as described above. If <file> is ?.?. filenames are read from standard
input. Use this option if you need to watch too many files to pass in as command line argu-
ments.
-m, --monitor
Instead of exiting after receiving a single event, execute indefinitely. The default behaviour
is to exit after the first event occurs.
-d, --daemon
Same as --monitor, except run in the background logging events to a file that must be specified
by --outfile. Implies --syslog.
-o, --outfile <file>
Output events to <file> rather than stdout.
-s, --syslog
Output errors to syslog(3) system log module rather than stderr.
-r, --recursive
Watch all subdirectories of any directories passed as arguments. Watches will be set up recur-
sively to an unlimited depth. Symbolic links are not traversed. Newly created subdirectories
will also be watched.
Warning: If you use this option while watching the root directory of a large tree, it may take
quite a while until all inotify watches are established, and events will not be received in
this time. Also, since one inotify watch will be established per subdirectory, it is possible
that the maximum amount of inotify watches per user will be reached. The default maximum is
8192; it can be increased by writing to /proc/sys/fs/inotify/max_user_watches.
-q, --quiet
If specified once, the program will be less verbose. Specifically, it will not state when it
has completed establishing all inotify watches.
If specified twice, the program will output nothing at all, except in the case of fatal errors.
--exclude <pattern>
Do not process any events whose filename matches the specified POSIX extended regular expres-
sion, case sensitive.
--excludei <pattern>
Do not process any events whose filename matches the specified POSIX extended regular expres-
sion, case insensitive.
-t <seconds>, --timeout <seconds>
Exit if an appropriate event has not occurred within <seconds> seconds. If <seconds> is zero
(the default), wait indefinitely for an event.
-e <event>, --event <event>
Listen for specific event(s) only. The events which can be listened for are listed in the
EVENTS section. This option can be specified more than once. If omitted, all events are lis-
tened for.
-c, --csv
Output in CSV (comma-separated values) format. This is useful when filenames may contain
spaces, since in this case it is not safe to simply split the output at each space character.
--timefmt <fmt>
Set a time format string as accepted by strftime(3) for use with the ?.T?.conversion in the
--format option.
--format <fmt>
Output in a user-specified format, using printf-like syntax. The event strings output are lim-
ited to around 4000 characters and will be truncated to this length. The following conversions
are supported:
%w This will be replaced with the name of the Watched file on which an event occurred.
%f When an event occurs within a directory, this will be replaced with the name of the File which
caused the event to occur. Otherwise, this will be replaced with an empty string.
%e Replaced with the Event(s) which occurred, comma-separated.
%Xe Replaced with the Event(s) which occurred, separated by whichever character is in the place of
?.?.
%T Replaced with the current Time in the format specified by the --timefmt option, which should be
a format string suitable for passing to strftime(3).
EXIT STATUS
0 The program executed successfully, and an event occurred which was being listened for.
1 An error occurred in execution of the program, or an event occurred which was not being lis-
tened for. The latter generally occurs if something happens which forcibly removes the inotify
watch, such as a watched file being deleted or the filesystem containing a watched file being
unmounted.
2 The -t option was used and an event did not occur in the specified interval of time.
EVENTS
The following events are valid for use with the -e option:
access A watched file or a file within a watched directory was read from.
modify A watched file or a file within a watched directory was written to.
attrib The metadata of a watched file or a file within a watched directory was modified. This
includes timestamps, file permissions, extended attributes etc.
close_write
A watched file or a file within a watched directory was closed, after being opened in writeable
mode. This does not necessarily imply the file was written to.
close_nowrite
A watched file or a file within a watched directory was closed, after being opened in read-only
mode.
close A watched file or a file within a watched directory was closed, regardless of how it was
opened. Note that this is actually implemented simply by listening for both close_write and
close_nowrite, hence all close events received will be output as one of these, not CLOSE.
open A watched file or a file within a watched directory was opened.
moved_to
A file or directory was moved into a watched directory. This event occurs even if the file is
simply moved from and to the same directory.
moved_from
A file or directory was moved from a watched directory. This event occurs even if the file is
simply moved from and to the same directory.
move A file or directory was moved from or to a watched directory. Note that this is actually
implemented simply by listening for both moved_to and moved_from, hence all close events
received will be output as one or both of these, not MOVE.
move_self
A watched file or directory was moved. After this event, the file or directory is no longer
being watched.
create A file or directory was created within a watched directory.
delete A file or directory within a watched directory was deleted.
delete_self
A watched file or directory was deleted. After this event the file or directory is no longer
being watched. Note that this event can occur even if it is not explicitly being listened for.
unmount
The filesystem on which a watched file or directory resides was unmounted. After this event
the file or directory is no longer being watched. Note that this event can occur even if it is
not explicitly being listened to.
EXAMPLES
Example 1
Running inotifywait at the command-line to wait for any file in the ?.est?.directory to be accessed.
After running inotifywait, ?.at test/foo?.is run in a separate console.
% inotifywait test
Setting up watches.
Watches established.
test/ ACCESS foo
Example 2
A short shell script to efficiently wait for httpd-related log messages and do something appropriate.
#!/bin/sh
while inotifywait -e modify /var/log/messages; do
if tail -n1 /var/log/messages | grep httpd; then
kdialog --msgbox "Apache needs love!"
fi
done
Example 3
A custom output format is used to watch ?./test?. Meanwhile, someone runs ?.ouch ~/test/badfile;
touch ~/test/goodfile; rm ~/test/badfile?.in another console.
% inotifywait -m -r --format ?.:e %f?.~/test
Setting up watches. Beware: since -r was given, this may take a while!
Watches established.
CREATE badfile
OPEN badfile
ATTRIB badfile
CLOSE_WRITE:CLOSE badfile
CREATE goodfile
OPEN goodfile
ATTRIB goodfile
CLOSE_WRITE:CLOSE goodfile
DELETE badfile
BUGS
There are race conditions in the recursive directory watching code which can cause events to be missed
if they occur in a directory immediately after that directory is created. This is probably not fix-
able.
It is assumed the inotify event queue will never overflow.
AUTHORS
inotifywait is written and maintained by Rohan McGovern <rohan@mcgovern.id.au>.
inotifywait is part of inotify-tools. The inotify-tools website is located at: http://inotify-
tools.sourceforge.net/
SEE ALSO
inotifywatch(1), strftime(3), inotify(7)
inotifywait 3.14 March 14, 2010 inotifywait(1)
