is the file sorted? if so, a simple uniq -d foo.txt > dups.txt will do it..
I wrote one coding but I have 'Out of memory Error'
 What's the code look like? Someone here may be able to provide suggestions on how to make it more efficient if you post the snippet.

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

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