Execute a program periodically, showing output full screen

      watch [options] command options


                 Specify an interval n seconds to run command

                 Highlight the differences between successive updates

   --help        Display Help

   --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 might 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.

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.


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

“Advertising may be described as the science of arresting the human intelligence long enough to get money from it” ~ Stephen Leacock

Related Linux commands

at - Schedule a command to run once at a particular time.
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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