====== AWK - Delete non-consecutive duplicate lines ======

<code bash>
awk '!a[$0]++' contents.txt
</code>

----

Example

<file bash contents.txt>
aaaaa
  bbbbb
ccccc
ccccc
  ddddd
ddddd
    eeeee
  bbbbb
</file>

returns:

<code bash>
aaaaa
  bbbbb
ccccc
  ddddd
ddddd
    eeeee
</code>