The Command-Line Interface (CLI), also called Terminal; Console; Command Prompt, is a way to interact with a computer. Unlike in a Graphical Interface, where you use your mouse and on-screen buttons, in a CLI all interaction is done with the keyboard, through a Text Interface.
Old-time Windows users might be familiar with MS-DOS, which features a Command-Line Interface. However, the Unix CLI is a much more powerful tool than MS-DOS.
On Unix, a CLI starts out something like this:
johndoe@computer12 /home/johndoe $ █
█– indicates where you can type.
The above combined is called the command prompt. It tells you who you are, on which machine you are, and where you are within the machine.
Unlike on Windows where paths look like
C:\Users\John Doe, on Unix paths look like
/home/johndoe. Spaces are allowed but not common as they tend to cause problems.
After opening a terminal window, the user
ls, and hits Return. This is the command to show the contents of the current directory.
johndoe@computer12 /home/johndoe $ ls documents letter.txt johndoe@computer12 /home/johndoe $ █
There are two files:
documents (a directory) and
letter.txt. Directories are typically shown in bold.
Next, John wants to see the contents of
letter.txt. He enters the command
cat, followed by the filename.
johndoe@computer12 /home/johndoe $ cat letter.txt Dear Reader, This is an example text file. Yours truly, John Doe johndoe@computer12 /home/johndoe $ █
To navigate to the
documents directory, John types
cd (change directory), followed by the name of the directory.
johndoe@computer12 /home/johndoe $ cd documents johndoe@computer12 /home/johndoe/documents $ █
You can see that the command prompt has changed, and he is now inside the documents directory. John can then type
ls again to see what's inside.
To go back to the parent directory, he types
johndoe@computer12 /home/johndoe/documents $ cd .. johndoe@computer12 /home/johndoe $ █
For a list of basic commands, please refer to basics