The Shell

Sometimes, you may want to interact with the operating system in a more direct way. A traditional way to do this is to do it through the shell.

The shell is a command line interface to the operating system. It is a program that wraps around the operating system kernel, and allows you to directly execute system calls and commands to interact with the operating system.

There are many various shells that are available on Linux, such as:

  • The Bourne shell (sh)
  • The Bourne-again shell (bash)
  • The Korn shell (ksh)
  • The Z shell (zsh)
  • The Friendly Interactive Shell (fish)

Ultramarine Linux uses the Z Shell as its default shell, combined with the Starship Prompt for a more clean interface.

To learn more about shell scripting, you can watch this Bash introduction video by Fireship here:

NOTE: The Z shell is mostly compatible with Bash, so most of the knowledge you will learn will be mostly applicable in Ultramarine Linux.

The Z shell is also used Kali Linux and newer versions of macOS (Catalina and newer).

Interacting with the shell

To start using the shell, open the Terminal app.

The GNOME Terminal

You will be greeted with a prompt, simply type in the command you want to execute, and press Enter⏎.

To change directories, type cd followed by the path you want to change to.

cd /home/user/Documents

To list the contents of a directory, type ls.

To read a file to the terminal, type cat followed by the path to the file.

cat /home/user/Documents/README.md

To delete a file, type rm followed by the path to the file.

rm /home/user/Documents/README.md

To delete a full directory, recursively delete it by typing rm -r followed by the path to the directory.

rm -r /home/user/Documents

Most users will usually execute rm -rf instead of rm -r. The -f flag is used to force the deletion of a file or directory.

To create a new file, type touch followed by the path to the file.

touch /home/user/Documents/newfile.txt

To create a new directory, type mkdir followed by the path to the directory.

mkdir /home/user/Documents/newdir

To move or rename a file or directory, type mv followed by the path to the file or directory, and then the new path.

mv /home/user/Documents/newfile.txt /home/user/Documents/newfile2.txt

To know more about each command, open the manual by typing man followed by what you want to learn about

man sudo

This will open less, an app that allows you to read through long lines of text as a scrollable page.

To exit less press Q.

Most commands will also have a -h or --help flag, which tells you more about the command.

The Pipeline

Linux offers a way for inter-process communication through pipes.

The pipeline you to transfer data from one process to another, and is used to execute commands in parallel.

echo "Hello World" | wc -w

This calls the wc (word count) command, which counts the number of words in the text. Then pipes the output of echo to it, which then outputs the number of words. This is a very simple example of a pipeline.

A named pipe is created by using > instead of |.

echo "Hello World" > pipe.txt

This pipes the output of echo to the named pipe pipe.txt, which is now a file.

Executing a file

To execute a program, you must first make sure that the file is executable. This is done by using the chmod command.

chmod +x /path/to/exec

Then you can execute the file by directly pointing to it.

/path/to/exec

For files in your current folder, you must use ./ before the file name.

./exec