WATCH

Section: Linux User's Manual (1)
Updated: 1999 Apr 3
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NAME

watch - 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

: 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.)

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.

This document was created by man2html, using the manual pages.
Time: 00:57:10 GMT, April 25, 2024