inotifywait, fsnotifywait - wait for changes to files using
inotify or fanotify
inotifywait [-hcmrPq] [-e <event> ]
[-t <seconds> ] [--format <fmt> ]
[--timefmt <fmt> ] <file> [ ... ]
fsnotifywait [-hcmrPqIFS] [-e <event> ]
[-t <seconds> ] [--format <fmt> ]
[--timefmt <fmt> ] <file> [ ... ]
inotifywait efficiently waits for changes to files using
Linux's inotify(7) interface. It is suitable for waiting for changes
to files from shell scripts. It can either exit once an event occurs, or
continually execute and output events as they occur.
fsnotifywait is similar to inotifywait but it is
using Linux's fanotify(7) interface by default. If explicitly
specified, it uses the inotify(7) interface.
inotifywait and fsnotifywait 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.
- -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
arguments.
- -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.
- -P,
--no-dereference
- Do not follow symlinks.
- -r, --recursive
- Watch all subdirectories of any directories passed as arguments. Watches
will be set up recursively 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 for the subset of files whose filenames match
the specified POSIX regular expression, case sensitive.
- --excludei
<pattern>
- Do not process any events for the subset of files whose filenames match
the specified POSIX regular expression, case insensitive.
- --include
<pattern>
- Process events only for the subset of files whose filenames match the
specified POSIX regular expression, case sensitive.
- --includei
<pattern>
- Process events only for the subset of files whose filenames match the
specified POSIX regular expression, 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 listened 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.
- --no-newline
- Don't print newline symbol after user-specified format in the --format
option.
- --format
<fmt>
- Output in a user-specified format, using printf-like syntax. The event
strings output are limited 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. When an event occurs within a Watched directory or when watching
with fanotify, this will be replaced with the name of the Directory in
which the event occurred.
- %f
- When an event occurs within a Watched directory or when watching with
fanotify, 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 `X'.
- %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).
- %0
- Replaced with NUL.
- %n
- Replaced with Line Feed.
The following additional options are available:
- -I, --inotify
- Watch using inotify.
- -F, --fanotify
- Watch using fanotify (default). fanotify support for reporting events with
inotify compatible information was added in kernel v5.9. With older
kernels the command will fail. As of kernel v5.12, fanotify requires admin
privileges.
- -S, --filesystem
- Watch entire filesystem of any directories passed as arguments using
fanotify.
- 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 listened 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.
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 writable 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 move 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.
Running inotifywait at the command-line to wait for any file in
the `test' directory to be accessed. After running inotifywait, `cat
test/foo' is run in a separate console.
% inotifywait test
Setting up watches.
Watches established.
test/ ACCESS foo
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
A custom output format is used to watch `~/test'. Meanwhile,
someone runs `touch ~/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
Enforce file permissions in directory `~/test'
inotifywait -qmr -e 'moved_to,create' --format '%w%f%0' --no-newline ~/test |\
while IFS= read -r -d '' file
do
chmod -v a+rX "$file"
done
When using inotifywait, the filename that is outputted is not
guaranteed to be up to date after a move because it is the inode that is
being monitored. Additionally, none of the observed operations are
guaranteed to have been performed on the filename inotifywait was instructed
to monitor in cases when the file is known by several names in the
filesystem.
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 fixable.
It is assumed the inotify event queue will never overflow.
inotifywait was started by Rohan McGovern, and is currently
maintained by Eric Curtin and Radu Voicilas.
https://www.openhub.net/p/inotify-tools/contributors/summary gives you a
more complete list of contributors.
inotifywait is part of inotify-tools. The inotify-tools website is
located at: https://github.com/inotify-tools/inotify-tools/wiki