Overview

Most computer Operating Systems (OS) provide a graphical user interface (GUI or “gooey”) to interact with systems through point-and-click mouse movements. However, using the command-line interface (CLI) provides a more concise and powerful means to control a program or OS. Moreover, using programs with a CLI are usually easier to automate via scripting, which is a necessity for any serious developer, programmer, software engineer, or computer scientist.

Note: the words directory and folder are used synonymously.

pwd
Print the full filename of the current working directory.

$ pwd

ls
List the contents of the current directory.

$ ls

cd ..
The change directory and double period combination will move to the parent directory of the current directory.

$ cd ..

cd ~
The change directory and ~ (tilde) combination will return to the home directory. It is an alternative to using the $HOME command.

$ cd ~

cd /
The change directory and / (forward slash) combination will return to the root directory.

$ cd /

Creating Directories

mkdir
Make directory is used to create a new directory in the current directory or in another directory. It can also create multiple directories by providing a list of file paths, separated by spaces.

# Create a new directory in the current directory.
$ mkdir dev_projects
$ ls
dev_projects/

# Create a new directory in another directory.
$  mkdir dev_projects/test_1
$ ls dev_projects/
test_1/

# Create multiple directories in another directory.
$ mkdir dev_projects/ex_1 dev_projects/ex_2
$ ls dev_projects/
ex_1/  ex_2/

Creating Files

touch
Touch can create a new file in the current directory or another directory. It can also create multiple files by providing a list of file paths, separated by spaces.

# Create new file in current directory.
$ touch test.py
$ ls
test.py

# Create new file in another directory.
$ touch dev_env/hello-world.py
$ ls dev_env/
hello-world.py

# Create multiple files in another directory.
$ touch dev_env/ex1.py dev_env/ex2.py
$ ls dev_env/
ex1.py  ex2.py

ls -lSh
Use ls (list directory contents), the -l (long listing format), -S (sort by file size), and -h (human readable) flags to view additional information.

$ ls -lSh test_env/

# Total in Kilobytes.
total 4.0K

# The leading dash (-) means this is a file.
-rw-rw-r-- 1 user user 19 Feb 19 06:41 example.py

Removing Files

rm
The remove command is used to delete a single file or multiple files.

# Remove a single file.
$ ls
example.py

$ rm example.py 

# Remove multiple files at once.
$ ls
note_1  note_2  note_3

$ rm note_1 note_2
$ ls
note_3

Removing Directories

rmdir
The remove directory command will only delete a completely empty directory.

$ ls
ex_1/  ex_2/  test_1/

$ rmdir test_1/
$ ls
ex_1/  ex_2/

rm -rf
The rm command in conjunction with the -rf flag will delete the directory and all files and folders inside. This is done with recursive force, using an approach called recursion.

Use this command with extreme caution!

$ ls
ex_1/  ex_2/

$ rm -rf ex_1/
$ ls
ex_2/

Summary

✔️ ls -lSh - list a directory’s contents, sorted by file size.

✔️ cd - change to a different directory.

✔️ pwd - print the current working directory’s location.

✔️ touch - create a new file or update a file’s timestamp.

✔️ mkdir - make a new directory.

✔️ rm - remove a file.

✔️ rmdir - remove an empty directory.

✔️ rm -rf - permanently remove a directory and its contents (caution is advised).