Using Windows/DOS shell/batch commands, how do I take a file and only keep unique lines?

Question

Say I have a file like:

apple
pear
lemon
lemon
pear
orange
lemon

How do I make it so that I only keep the unique lines, so I get:

Answer 1

Run PowerShell from the command prompt.

Assuming the items are in a file call fruits.txt, the following will put the unique lines in uniques.txt:

type fruits.txt | Sort-Object -unique | Out-File uniques.txt