Using a Caesar Cipher shifted $6$ positions $($a $->$ g$),$ encode the following message:

attackatdawn

This can be done by hand or with the following command in a Kali terminal window that takes the first string and translates the letter in the second string into the letter in the same position of the third string.

echo 'attackatdawn' $|$ tr 'abcdefghijklmnopqrstuvwxyz' 'ghijklmnopqrstuvwxyzabcdef'

If you don't want to type out all those letters, use a short cut that the tr command gives us

echo 'attackatdawn' $|$ tr $\text{'}$a$-$z$\text{'}\text{'}$g$-$za$-$f$\text{'}$

type man tr or tr $--$help to see what else the translate command can do