Killing all instances of Chrome on the command-line?

Try using pkill(1).

pkill chrome

ps aux | grep chrome | awk ' { print $2 } ' | xargs kill -9

pgrep chrome | xargs kill -9

ps aux | awk '/chrome/ { print $2 } ' | xargs kill -9

The latter is more "elegant" as it will not pick up the actual pid for "grep chrome" inside of its ps listing

:-)

Some systems may also have useful programs such as killall and pidof (which is actually provided by the System V killall5):

killall chrome
kill -9 `pidof chrome`

Both of these should accomplish what you are asking.

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