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watch - Online in the Cloud

Run watch in OnWorks free hosting provider over Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator

This is the command watch that can be run in the OnWorks free hosting provider using one of our multiple free online workstations such as Ubuntu Online, Fedora Online, Windows online emulator or MAC OS online emulator



watch - execute a program periodically, showing output fullscreen


watch [options] command


watch runs command repeatedly, displaying its output and errors (the first screenfull).
This allows you to watch the program output change over time. By default, the program is
run every 2 seconds. By default, watch will run until interrupted.


-d, --differences [permanent]
Highlight the differences between successive updates. Option will read optional
argument that changes highlight to be permanent, allowing to see what has changed
at least once since first iteration.

-n, --interval seconds
Specify update interval. The command will not allow quicker than 0.1 second
interval, in which the smaller values are converted.

-p, --precise
Make watch attempt to run command every interval seconds. Try it with ntptime and
notice how the fractional seconds stays (nearly) the same, as opposed to normal
mode where they continuously increase.

-t, --no-title
Turn off the header showing the interval, command, and current time at the top of
the display, as well as the following blank line.

-b, --beep
Beep if command has a non-zero exit.

-e, --errexit
Freeze updates on command error, and exit after a key press.

-g, --chgexit
Exit when the output of command changes.

-c, --color
Interpret ANSI color and style sequences.

-x, --exec
command is given to sh -c which means that you may need to use extra quoting to get
the desired effect. This with the --exec option, which passes the command to
exec(2) instead.

-h, --help
Display help text and exit.

-v, --version
Display version information and exit.


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


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 "'"'$$'"'"

To see the effect of precision time keeping, try adding -p to

watch -n 10 sleep 1

You can watch for your administrator to install the latest kernel with

watch uname -r

(Note that -p isn't guaranteed to work across reboots, especially in the face of ntpdate
or other bootup time-changing mechanisms)

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