Level goal

The password for the next level is stored in the file data.txt and is the only line of text that occurs only once.

Login

ssh bandit8@bandit.labs.overthewire.org -p 2220
dfwvzFQi4mU0wfNbFOe9RoWskMLg7eEc

Doc

sort (1)             - sort lines of text files
uniq (1)             - report or omit repeated lines
    -c, --count           prefix lines by the number of occurrences
    -u, --unique          only print unique lines
| -pipe operator

Solution

We pipe the ouput of sort (in order to get the identical lines one after the other) and pipe the output to unique using the flags -c (counting just to make sure) and -u(unique)

bandit8@bandit:~$ sort data.txt | uniq -cu
      1 4CKMh1JI91bUIZZPXDqGanal4xvAg0JM