How to use uniq Unix command and specify input and output file?

Question

I'm confusing use of uniq command, can anyone explain this command and how to use it?

How to use uniq without specifying any option?

Any example would be helped and appreciated

warl0ck · Answer 1 · 2013-03-08 06:25:48Z

up vote 1 down vote

uniq read file line-by-line, and only consider a duplicate when the current line is exactly the same as the last line,

i.e for a input file like this,

You'll get an output like this,

1
2
1

To use it, you can either run it though a pipe, i.e

command | uniq

Or get the input from a file like this,

uniq < input > output

edited Mar 8 at 6:25

answered Mar 8 at 3:06

warl0ck
10.8k11166

	I have to downvote this because it doesn't appear to answer the question at all. The question is about `uniq`, not `sort`. Data does need to be sorted for `uniq` to work, but that is not included here. – jordanm Mar 8 at 6:19
	@jordanm ah, I take it wrong, answer updated, thanks for pointing out – warl0ck Mar 8 at 6:26
	However, all my uses of `uniq` combine with `sort` – Bernhard Mar 8 at 12:30
	Downvote removed – jordanm Mar 8 at 15:37
	For completeness, I'd suggest including a demonstration of how `uniq` and `sort` work together; I agree that `uniq` is most useful when combined with `sort`. – davidcl Mar 8 at 17:06

1 Answer