the many greps

[JTW at MIT-XX.ARPA]

From:  John T. Wroclawski <JTW at MIT-XX.ARPA>

	So why doesn't somebody do just that?  There is a reason: the three
	greps interpret three different forms of regular expression.  You
	can't take an arbitrary shell script which uses, say, 'grep' and
	substitute 'egrep' everywhere without first scrutinizing each regular
	expression to make sure it doesn't have parentheses, vertical bars,
	etc.

Now wait a minute. What's to prevent the (one) unified grep from basing
it's choice of algorithm partly on whether that algorithm can handle the
particular regular expr grep was given as an argument?
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