There were 11 bash challenges with a one month Hack The Box VIP+ prize to the first person who completes all of them.

1. How many?

Use the smallest amount of code to echo the number of characters in the string ‘a’.

Mystiko{echo ${#a}}

2. UpPeR or LOwErcaSe?

Use the smallest amount of code to echo the variable ‘a’ all lower case.

Mystiko{echo ${a,}}

3. Calculating a float?

Use the smallest amount of code to echo the answer of 2.50000 when dividing 5 by 2 on the command line.

Mystiko{echo "scale=5;5/2"|bc}

4. Alt+126

Use the smallest amount of code to list the directory contents of the user mystiko.

Mystiko{ls ~mystiko}

5. Where am I?

Use the smallest amount of code to return to your last directory.

Mystiko{cd -}

6. AKA

Can some one help me make it easier to type the following command in just by typing in the letters www
python3 -m http.server 8888

Mystiko{alias www='python3 -m http.server 8888'}

7. Read that file!!

You have a file. You need to read it. There are a few caveats:

It can only be read in a terminal. You must only use a binary that contains two letters. You cannot use an editor. The flag is the md5 hash of the terminal answer after you have run it.

[connor@fedora Desktop]$ wget -O not_the_flag.txt
[connor@fedora Desktop]$ nl not_the_flag.txt | openssl md5
MD5(stdin)= de87beaf3d7a30134c0de342dcc43a76


8. Enumeration: “Ubuntu what?”

Find a way to get the following (at a minimum) information for a box that you have just accessed.

PRETTY_NAME=”Ubuntu 21.10”

This information is found in /etc/lsb-release and /etc/os-release.
I thought nl /etc/* was technically correct, but managed to guess the flag: Mystiko{nl /etc/*release}

9. My External IP

I need to find only my external IP address. How can I do that in the shortest BASH terminal command?

There are various websites that give you your IP, and seemed to have the shortest URLs.
Mystiko{curl} was not accepted, but Mystiko{curl} was.

10. Hidden

You are setting up a CTF challenge for your friends but want to ensure that they cannot see your history.
What is the shortest piece of code that you can use to hide your commands?

By default, commands with a space entered before them will not be saved in bash history.
Mystiko{ }

11. Delete the file - quickly!!!

You have a file emailed to you by a spy you just met in a coffee shop.
You must delete it as quickly as you can. You check the file first and
notice that it has an ‘i’ attribute set. What is the shortest piece of
code that you can use to delete the file called “a” while not running as root user?

Mystiko{sudo chattr -i a;rm a}

I ended up winning the prize!