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Linux / Unix Command: watch
Command Library

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.)  


Important: Use the man command (% man) to see how a command is used on your particular computer.

>> Linux/Unix Command Library

>> Shell Command Library

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