watch - execute a program periodically, showing output fullscreen
watch [-dhv] [-n <seconds>] [--differences[=cumulative]] [--help]
[--interval=<seconds>] [--version] <command>
watch runs command repeatedly, displaying its output (the first screenfull).
This allows you to watch the program output change over time.
By default, the program is run every 2 seconds; use -n or --interval to
specify a different interval.
The -d or --differences flag will highlight the differences between
successive updates. The --cumulative option makes highlighting
"sticky", presenting a running display of all positions that have ever
changed.
watch will run until interrupted.
Note that command is given to "sh -c" which means that you may need to
use extra quoting to get the desired effect.
Note that POSIX option processing is used (i.e., option processing
stops at the first non-option argument). This means that flags after
command don't get interpreted by watch itself.
To watch for mail, you might do
watch -n 60 from
To watch the contents of a directory change, you could use
watch -d ls -l
If you're only interested in files owned by user joe, you might use
watch -d 'ls -l | fgrep joe'
To see the effects of quoting, try these out
watch echo $$
watch echo '$$'
watch echo "'"'$$'"'"
You can watch for your administrator to install the latest kernel with
watch uname -r
(Just kidding.)
Upon terminal resize, the screen will not be correctly repainted until
the next scheduled update. All --differences highlighting is lost on
that update as well.
Non-printing characters are stripped from program output. Use "cat -v"
as part of the command pipeline if you want to see them.
The original watch was written by Tony Rems <[email protected]> in
1991, with mods and corrections by Francois Pinard. It was reworked
and new features added by Mike Coleman <[email protected]> in 1999.
1999 Apr 3 WATCH(1)
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