watch

Execute a program periodically, showing output full screen

Syntax
      watch [options] command options

Options

   -n
   --interval=n 
                 Specify an interval n seconds to run command

   -d
   --differences[=cumulative]]
                 Highlight the differences between successive updates

   -h
   --help        Display Help

   -v
   --version     Display version

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.

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.

POSIX option processing is used (i.e., option processing stops at the first non-option argument). This means that command_options 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.

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Related:

builtin - Run a shell builtin
crontab - Schedule a command to run at a later time
chroot - Run a command with a different root directory
exec - Execute a command
if - Conditionally perform a command
nohup - Run a command immune to hangups
su - Run a command with substitute user and group id
watch - Execute/display a program periodically
.period - Run commands from a file
Equivalent Windows command: SCHTASKS - Manage scheduled tasks.


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