Inserting Blank Line into File (sed/awk/?)

[Root Boy Jim]

>In article <ED.91Mar15201957 at lvw6.lvw.loral.com> ed at lvw6.lvw.loral.com (Ed Allen) writes:
>>Now for the 'sed' solution....
>>sed -n -e '{N;N;p;a\
>>
>>}' filename

Most of it anyway. Works if the number of lines is a multiple of three.
Extra line or two gets eaten.

Anyway, here's a single line solution without the same bug:

	sed -n -e '$p;N;$p;N;h;s/.*//;H;x;p'

I think TC is right about avoiding sed in cases like this.
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