uniq command takes in a sorted file and reports duplicated lines. With the proper options, it can be used to omit or report unique or repeated lines.
If we use the
uniq command on an unsorted list, it will report unexpected results, so make sure you
$ sort test.txt | uniq
The example file here simply lists the names of a few people. If we
sort then call uniq, it will return all names in the file, just once.
$ cat names.txt Bob Chase Jon Clara Bob Theresa Jon Billy Jonathan Clara Jonathan Bob Jonny $ sort names.txt | uniq Billy Bob Chase Clara Jon Jonathan Jonny Theresa
To output lines that have repeated elements, we pass in the
$ sort names.txt | uniq -d Bob Clara Jon Jonathan
To output lines that occur just once, pass in the
$ sort names.txt | uniq -c Billy Chase Jonny Theresa
-c option, we can find how many times each occurrence occurs.
$ sort names.txt | uniq -c 1 Billy 3 Bob 1 Chase 2 Clara 2 Jon 2 Jonathan 1 Jonny 1 Theresa
Here are a list of the most-used options. Check out the
man page for more.
-d- output only unique lines. This is the default setting.
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