Re: [9fans] text utility

[Geoff Collyer <geoff@collyer.net>]

I'm pretty sure it was Doug McIlroy who used

	rev <dict | sort >rhymdict

to produce a rhyming dictionary.  To find rhyming words, you'd reverse
the suffix of a word, look that up and reverse the result:

	look `{echo suffix | rev} rhymdict | rev

This is described in a memo called `Webster's 2nd on the head of a
pin' and dates from the mid-1970s.  (I have a copy somewhere.)

As for tac,

	tail -1000000000r

does the job for most files of interest (those under a billion lines).
I just tried it on a file of ~250,000 lines; it's quite quick.
Alternatively,

	awk '{print NR, $0}' | sort -nr | sed 's/^[0-9]+ //'

does the job more slowly.