====== SED - Delete - Delete duplicate, nonconsecutive lines from a file ======

<WRAP important>
**WARNING:**  Beware not to overflow the buffer size of the hold space, or else use GNU sed.
</WRAP>

<code bash>
sed -n 'G; s/\n/&&/; /^\([ -~]*\n\).*\n\1/d; s/\n//; h; P'
</code>