The traditional approach is to sort your file first, then all duplicates will appear one after another. To sort a huge amount of data, the best approach is to divide it up into small parts and sort these first and then do a Merge Sort from the sorted parts. During that merging you can also already output the duplicates easily.

In reply to Re: Find duplicate lines from the file and write it into new file. by Corion
in thread Find duplicate lines from the file and write it into new file. by anna_here

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