Uniq
uniq is a Unix utility which, when fed a text file, outputs the file with adjacent identical lines collapsed to one. It is a kind of filter program. Typically it is used after sort. It can also output only the duplicate lines (with the -d option), or add the number of occurrences of each line (with the -c option).
An example:
To see the list of lines in a file, sorted by the number of times each occurs:
- sort file|uniq -c|sort -n
Using uniq like this is common when building pipelines in shell scripts.
