remove same line in a file

[we2aresame]

I have a file like:
aaa
bbb
aaa
ccc
aaa
ddd
now, I try to only keep one line represent the lines which include same data, that means, the new file will be like:
aaa
bbb
ccc
ddd
would you tell me how to do it, thanks.

 

[Ygor]

sort -u

 

[we2aresame]

thanks, but if the file like:
aaa
ccc
bbb
aaa

the result should be:

aaa
ccc
bbb

I just want to remove the same data lines, sort maybe not the best way, thanks.

 

[CaKiwi]

Try this (untested)

awk '{if (!a[$0]){a[$0]=1;print}}' infile > outfile

CaKiwi

"I love mankind, it's people I can't stand" - Linus Van Pelt

 

[sampsonr]

or how about just:

sort infile | uniq