On Monday 2 February 2004, nickm at go2.ie (Nick Murtagh) wrote:
>Brian Foster wrote:
>> ( 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? )
>>I don't understand - uniq seems to do what you are suggesting,
>ie given unsorted input, adjacent duplicates are removed.
uniq does exactly that. But if what you want is a file with all
duplicates removed then you must sort first, in order to remove ALL
duplicates. And if you want the action of uniq -u i.e. to get all the
uniq lines in the file(s) you also have to have sorted input - otherwise
how is uniq to know that a line IS unique. Of course you could write a
unique which does work with unsorted input, but it would take
exponentially larger amounts of memory.
Niall
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