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.
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