Comments on: Watch – A Useful Linux Command You May Have Never Heard Of

By: Artem Russakovskii

Artem Russakovskii — Tue, 13 Mar 2012 10:36:06 +0000

Don't think you can do that with watch. If you want to detect file system changes, I suggest you look into lsyncd or inotify-tools.

By: soi

soi — Tue, 13 Mar 2012 10:04:43 +0000

Hi Artem,

I wonder how to have "watch" execute a command or an application for me after its detection of something "new" created or changed? For example, I issue the command $watch 'ls /home/user/' and want to execute a script call upload.sh every time a new file created and detected by "watch"?

Thank you!

By: Thomas

Thomas — Thu, 11 Aug 2011 06:34:40 +0000

Nice and useful post. When I recover data from bad HDDs, I used frequent "df -h" in 2 minutes interval. So I think "watch -n 120 -d df -h" will make me free from frequent typing. Cheers!

By: Seabrook

Seabrook — Thu, 10 Feb 2011 21:46:39 +0000

Type the following:

watch 'tail -1 /var/log/secure >> /root/sechist'

to create a cumulative file of the last line of the
/var/log/secure file, sampling every two seconds.

Then execute the following to see only the changes

uniq /root/sechist

Do an su command in another window to generate
some changes for this command.

By: Abhiram

Abhiram — Sun, 06 Feb 2011 05:28:03 +0000

Hi!

Am trying to redirect the o/p of the watch command to a file.

For ex — watch -n 10 ps >> output.txt

This is giving the o/p in the file BUT, is adding these junk characters in addition. ALSO, it is NOT separating the outputs at different intervals. Its just mixing it all up.

Help needed to separate the outputs at diff intervals and NOT print the special characters!!

Regards

By: Kris

Kris — Wed, 02 Feb 2011 15:15:29 +0000

Love the reply. I hope my comment pushes you over $999,9999.00

By: Artem Russakovskii

Artem Russakovskii — Wed, 27 Oct 2010 08:52:05 +0000

Thanks for stopping by and commenting on a 3-year old article, and for your kind and not at all passive aggressive wish. I am in fact working on becoming a millionaire in this exact way. Moreover, I believe this very page will push me past the $999,999.

By: kisiel

kisiel — Wed, 27 Oct 2010 08:35:16 +0000

So you plan to become a millionaire without actually providing any value, as evidenced by this post, copied in haste from a man page. The best of luck with that.

By: jlampa

jlampa — Tue, 26 Oct 2010 19:12:27 +0000

While watch is pretty useful, a better solution in this case would be to use inotify / incron, which is like cron, but based on filesystem events instead of a schedule.

By: lakshmi

lakshmi — Tue, 26 Oct 2010 18:29:16 +0000

Learn something new everyday! Nice post.

By: redraven

redraven — Tue, 26 Oct 2010 16:27:34 +0000

I use this quite frequently:
watch -n 1 -d /usr/bin/sensors

By: Spyros

Spyros — Fri, 16 Oct 2009 07:48:25 +0000

Actually i have heard of the command but i must admit that i have really used it Nice post, though !

By: YB

YB — Thu, 26 Feb 2009 14:04:16 +0000

Thanks, Guy!
I was looking for a way to watch a certain part of a long output and your tailpipe solution was perfect!

By: Guy

Guy — Mon, 22 Sep 2008 10:59:59 +0000

Artem,
Just pipe it out to the tail function, try this:

watch -d 'ls -l /usr/bin | tail -n 50'

Works quite well. Now if it could only take an action when something changed, i.e., move files in a directory when we found changes to a directory.

By: Artem Russakovskii

Artem Russakovskii — Thu, 24 Jul 2008 17:14:38 +0000

Carlos, what I mean is, if you are trying to watch a long directory listing that doesn't fit the screen, screen would show you the top output of 'ls' for example, not the bottom.

By: Carlos from Philly

Carlos from Philly — Thu, 24 Jul 2008 13:54:58 +0000

Not sure what you mean by:
"Now if anyone knows how to make watch print the bottom part of the command output rather than the top, please post a comment."
But using the –no-title option eliminates the:
Every 5.0s: ls Thu Jul 24 09:53:45 2008
portion of the output, giving you only the result of the stuff in your quotes (at the specified interval and maintaining the specified options, of course).