OverTheWire Bandit: Level 7 to Level 8

The Goal

Find the password stored in data.txt next to the word millionth.

What I Did

Listed the directory to confirm the file:

bandit7@bandit:~$ ls
data.txt

Tried reading it with cat:

bandit7@bandit:~$ cat data.txt

A massive wall of text came out — thousands of lines, each containing a word and what looked like a password. Reading through it manually wasn’t an option.

I needed to find the specific line containing millionth. That’s exactly what grep is for:

bandit7@bandit:~$ grep "millionth" data.txt
millionth	dfwvzFQi4mU0wfNbFOe9RoWskMLg7eEc

One line. The password is right there next to the word.

What grep Actually Does

grep stands for Global Regular Expression Print. It reads through a file line by line, checks each line against a pattern you give it, and prints every line that matches.

The basic syntax is:

grep "pattern" filename

It’s case sensitive by default. grep "Millionth" would find nothing here because the word is lowercase. To make it case insensitive add -i:

grep -i "millionth" data.txt

Other useful flags:

Flag	What it does
-i	Case insensitive search
-n	Show line numbers
-v	Invert — show lines that do NOT match
-r	Search recursively through directories
-c	Count matching lines instead of printing them
-l	Print only filenames that contain a match

The Other Commands on This Level

This level lists several commands I didn’t need here but are worth understanding:

sort — sorts lines alphabetically or numerically. Almost always paired with uniq.

uniq — removes consecutive duplicate lines. sort data.txt | uniq is the standard combination for finding or removing duplicates.

strings — extracts readable text from binary files. When cat gives you garbage characters, strings pulls out only the human-readable parts.

base64 — encodes or decodes base64 data. base64 -d file decodes it back to the original content.

tr — translates or replaces characters. tr 'A-Z' 'a-z' converts uppercase to lowercase. tr -d '\n' removes all newline characters.

tar — bundles multiple files into one archive. tar -xf archive.tar extracts it.

gzip / bzip2 — compression tools. gzip -d file.gz and bzip2 -d file.bz2 decompress files.

xxd — shows a hex dump of a file. Used when you need to inspect raw bytes — common in reverse engineering and forensics.

| (pipe) — the most important operator in Linux. Takes the output of one command and feeds it as input to the next:

cat data.txt | grep "millionth"

This does exactly the same thing as grep "millionth" data.txt — two ways to get the same result. Pipes become essential when chaining multiple commands together.

What I Learned

grep is the go-to tool for searching inside files. When a file is too large to read manually, grep finds exactly what you need instantly.

The pipe operator chains tools together. Linux is built around small tools that each do one thing well. The power comes from combining them.

Reading a massive file with cat first showed me what the structure looked like — word on the left, password on the right — which confirmed that grep was the right approach.

Commands Used

Command	What it did
ls	Confirmed data.txt exists
cat data.txt	Showed the file structure — too large to read manually
grep "millionth" data.txt	Found the exact line containing the password