Which, btw, can be achieved by GNU's uniq which - my guess - is the most efficient way to do that.

That isn't what uniq does. It removes adjacent duplicate lines only. This is why everyone sorts before running uniq.

$ echo -e "foo\nbar\nfoo" | uniq
foo
bar
foo
$ echo -e "foo\nbar\nfoo" | sort | uniq
bar
foo
$

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In reply to Re^2: Possible faster way to do this? by hippo
in thread Possible faster way to do this? by Anonymous Monk

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