The uniq command finds the unique lines in a given input (stdin or a filename command line argument) and either reports or removes the duplicated lines.
This command only works with sorted data. Hence, uniq is often used with the sort command.
To produce the unique lines (all lines in the input are printed and duplicate lines are printed once), use this:
$ cat sorted.txt bash foss hack hack $ uniq sorted.txt bash foss hack
Alternatively, use this:
$ sort unsorted.txt | uniq
Display only unique lines (the lines that are not repeated or duplicated in the input file):
$ uniq -u sorted.txt bash foss
Alternatively, use this command:
$ sort unsorted.txt | uniq -u
To count how many times each of the lines appears in the file, ...
