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