Another linux command, I find very useful, this is a command that helps you search for strings/text within documents. There are a whole lot of uses for it, but I will leave you to explore that yourself.
Its simplest form is:
grep <word> <in file> => grep "dog" animals.txt
The above looks for dog in a text file called animal.txt
There are flags/options you can set with the command to make things easier.
-x = exclusive, exact match -v = everything but -i = I do not care about case
and many more.
You can also use  and ^ to help make your search more refined.
grep ^a* fruits.txt
Finds fruits that have a in them
grep ^a.p fruits.txt
Finds fruits that begin with an a and followed a random letter and then by a p.
grep ^[a-p] fruits.txt
Find all text that begin with an a through to P in fruits.txt
Go ahead and play with grep!
Lastly, grep can search through huge files very quickly, and outputs can be overwhelming, eg. log files. To make it easier, and this can be used for most linux commands,you can pipe commands through each other.
ps aux | grep 'root'| less
This simply means, I am looking for root in the output of
ps aux but due to the volume outputted, I want to see them in pages, thus the use of
Go ahead and play with grep. Fun times ahead.