| Date: Mon, 02 Feb 2004 20:12:10 +0100
| From: Brian Foster <blf at utvinternet.ie>
|[ ... ]
| be aware, however, that both uniq(1) and `comm'
| require the input to be sorted.
| ( I must confess I have never understood why the
| input must be sorted. `uniq' could still deal
| with _adjacent_ duplicate lines (e.g., N and N+1),
| and `comm' could compare line N with line N.
| why the insistence on sorting? ) [ ... ]
sorry for replying to my own post.
the above is (almost) all gibberish.
uniq(1) does not require its input to be sorted,
unless you want to find/remove all duplicates.
comm(1) requires sorted input because making
a tri-state decision (file1-only, file2-only,
or both-files) on the basis of a line-by-line
(bi-valued) comparison is computationally infeasible.
now I just hope the work-related e-mail I sent
late last night is more coherent than the above
p.s. my clear(er?) memory now in the morning is it was
older, any maybe only non-GNU, versions of join(1)
which inexplicitly insisted on sorted input.
however, I note the GNU join man(1) page does not
mention sorting, so perhaps that nonsense has been
removed. or I am just imagining it?
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