One of the commands I use the most in the terminal is grep, even more than cd o ls.
grep It has many options and offers dissimilar possibilities, however I use the most conventional way possible, but let's start by explaining What is grep?
grep is simply a filter, it is a command that shows lines that match the filter we have declared.
For example, in our system we have the file / usr / share / doc / bash / FAQ and the content of this file is:
If you want to list the content in the terminal with the command cat (yes cat, like cat hehe) they can do it:
cat /usr/share/doc/bash/FAQ
Now, suppose we only want to list the line of that file that talks about the version, for this we use grep:
cat /usr/share/doc/bash/FAQ | grep version
Putting that in the terminal will only show you the line that contains "version" in that file, it will no longer show any line that does not contain that word.
What if I want to show everything except the version line?
That is, in the way I explained to you, everything that matches the filter would be shown, now I will show you how to make everything appear except what matches the filter:
cat /usr/share/doc/bash/FAQ | grep -v version
Do you notice the difference? ... simply adding -v It already makes a difference 
So if they put grep it will only show you what matches the filter, but if you put grep -v it will show you everything except the filter.
Well, this is where the post ends, just another tip that you might now look down on but… you have no idea how useful grep can be, it is seriously a life saver 
regards