Learning Linux Shell Scripting - Second Edition

The uniq command

The following are a few examples showing the usage of the uniq command:

• This command removes duplicate adjacent lines from the file:

    $ cat test
    aa
    aa
    cc
    cc
    bb
    bb
    yy
    zz
    $ uniq test

• This output removes the duplicate adjacent lines from test file, shown as follows:

    aa
    cc
    bb
    yy
    zz

• The next command only prints duplicate lines:

    $ uniq -d test

• Output:

    aa
    cc
    bb

• The following command prints the number of occurrences of all elements on an individual line:

    $ uniq -c test

• Output:

    2 aa
    2 cc
    2 bb
    1 yy
    1 zz