watch is a GNU command-line tool that runs the specified command repeatedly and displays the output on stdout so you can watch it change over time. By default, the command is run every 2 seconds, although this is adjustable with the -n secs argument. Since the command is passed to sh -c, you may need to encase it in quotes for it to run correctly.
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Syntax
watch [options] command [command options]
Example
watch "ps aux | grep php"
This will generate a list of processes every 2 seconds, filter for all lines that contain the word "php", and display the results on the screen. The output might look something like this:
Every 2s: ps aux | grep php Tue Jan 30 14:56:33 2007 reconst 30028 0.0 0.0 7044 2596 ? S Jan23 0:00 vim -r core/html_api.php cinonet 28009 0.0 0.2 20708 11064 ? SN Jan25 0:30 php5.cgi donoiz 23810 0.0 0.2 22740 10996 ? SN Jan27 0:30 php.cgi 43/pdf
The watch command is useful for viewing changes over time, like repeatedly running the ls -l command to watch a file's size change, or running ps as in the above example to monitor certain processes continuously.
Arguments
-d– Highlights differences between iterations-h– Displays a help message, then exits-n secs– Specifies the interval between executions of the command in seconds-t– Tells watch not to display the header-v– Prints version information, then exits
See also
External links
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