Section: Linux User's Manual (1)
Updated: 1999 Apr 3
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watch - execute a program periodically, showing output fullscreen
[-dhvt] [-n <seconds>] [--differences[=cumulative]] [--help] [--interval=<seconds>] [--no-title] [--version] <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
to specify a different interval.
flag will highlight the differences between successive updates. The
option makes highlighting "sticky", presenting a running display of all
positions that have ever changed. The
option turns off the header showing the interval, command, and current
time at the top of the display, as well as the following blank line.
will run until interrupted.
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
don't get interpreted by
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
Upon terminal resize, the screen will not be correctly repainted until the
next scheduled update. All
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.
was written by Tony Rems <firstname.lastname@example.org> in 1991, with mods and
corrections by Francois Pinard. It was reworked and new features added by
Mike Coleman <email@example.com> in 1999.
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