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

Use GNU sort utility:

sort -u file.txt

If you're on Windows and using Git, then sort and many more useful utilities are already here: C:\Program Files\Git\usr\bin\

Just add this path to your %PATH% environment variable.