WATCH (1)
execute a program periodically, showing output fullscreen
SYNOPSIS
watch
[-dhv] [-n <seconds>] [--differences[=cumulative]] [--help] [--interval=<seconds>] [--version] <command>
DESCRIPTION
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
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.
EXAMPLES
To watch for mail, you might do
To watch the contents of a directory change, you could use
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
You can watch for your administrator to install the latest kernel with
(Just kidding.)
BUGS
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.
AUTHORS
The original
watch
was written by Tony Rems <rembo@unisoft.com> in 1991, with mods and
corrections by Francois Pinard. It was reworked and new features added by
Mike Coleman <mkc@acm.org> in 1999.
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