#!/bin/bashecho '192.168.1.1 foobar' | grep -E '([0-9]{1,3}\.?){4}'echo '192.168.1.1 foobar' | grep '\([0-9]\{1,3\}\.\{0,1\}\)\{4\}'
Standard input is empty
192.168.1.1 foobar 192.168.1.1 foobar
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