The Goal

The password for Level 9 is the only line that appears exactly once in data.txt. All other lines are repeated.

The Approach

uniq -u prints only unique lines, but it only compares adjacent lines. Running it directly on the unsorted file still prints duplicates. The file needs to be sorted first so that identical lines end up next to each other, allowing uniq -u to work correctly:

bandit8@bandit:~$ cat data.txt | sort -d | uniq -u
password

Commands Covered

  • sort -d, sort lines in dictionary order
  • uniq -u, print only lines that appear exactly once (requires sorted input)