How does "Linux learning" know about a strange command?

How to understand a strange command?

Some commands can be used to understand the situation of a command itself, such as the absolute path of the command.

$which ls

Which searches for a command in the default path , returning the absolute path to the command.

$whereis ls

Whereis searches for a command in a relatively large range , returning the absolute path to the command .

$whatis ls

Whatis used a short sentence to introduce the order.

$man ls

Man queries a concise help manual . For most Linux-brought commands, when the author writes it, it comes with a help document that tells the user how to use the command.

(man can be said to be the best encyclopedia we know about Linux, it can not only tell you the features of Linux commands, but also query Linux system files and system calls.) If you want to learn more about Linux, you have to know how to use man to query related documents. )

$info ls

Info query For more detailed help information

In addition, in the shell, you can also use the UP arrow to view previously entered commands that were run.

You can also use

$history

To query the previous operation on the command line.

When a command runs, you can use Ctrl + C when you want to stop it halfway . If you just want to stop temporarily, use Ctrl + Z.

How does "Linux learning" know about a strange command?