watch



WATCH(1)                      Linux User’s Manual                     WATCH(1)




NAME

       watch - execute a program periodically, showing output fullscreen


SYNOPSIS

       watch  [-dhvt]  [-n  <seconds>]  [--differences[=cumulative]]  [--help]
       [--interval=<seconds>] [--no-title] [--version] <command>


DESCRIPTION

       watch runs command repeatedly, displaying its output (the first screen-
       full).   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.  The -t or --no-title 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.

       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.



                                  1999 Apr 3                          WATCH(1)

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