Re: uniq without sort <-------------- GURU NEEDED

gnuist006@gmail.com wrote:
> This is a tough problem, and needs a guru.
>
> I know it is very easy to find uniq or non-uniq lines if you scramble
> all of them and sort them. Its trivially
>
> echo -e "a\nc\nd\nb\nc\nd" | sort | uniq
>
> $ echo -e "a\nc\nd\nb\nc\nd"
> a
> c
> d
> b
> c
> d
>
> $ echo -e "a\nc\nd\nb\nc\nd"|sort|uniq
> a
> b
> c
> d
>
>
> So it is TRIVIAL with sort.
>
> I want uniq without sorting the initial order.
>
> The algorithm is this. For every line, look above if there is another
> line like it. If so, then ignore it. If not, then output it. I am
> sure, I can spend some time to write this in C. But what is the
> solution using shell ? This way I can get an output that preserves the
> order of first occurrence. It is needed in many problems.

$ echo -e "a\nc\nd\nb\nc\nd" | perl -lne'$x{$_}++||print'
a
c
d
b



John
--
Perl isn't a toolbox, but a small machine shop where you
can special-order certain sorts of tools at low cost and
in short order. -- Larry Wall