And to do it all at once as an inline edit: 
sort -uo file.txt file.txt

[download]

Update: For those that asked, sort -u file.txt > file.txt
will completely and happily change file.txt into a zero byte file, hence the need for the "o" flag.

In reply to Re: Re: Re: Detecting duplicate entries by turnstep
in thread Detecting duplicate entries by r.joseph

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