# Hola , Linux 👋 | Beyond Shell(s)


## What is Hola, Linux 👋  ?
-  **Hola, Linux 👋** is a project that you can depend on it as a starter code for your brain 🧠 to rebuild Linux concepts.

#### ***One Shell, Many Sessions***.
➡️ I want you to be quiet 😔 and divide the concept of shell **logically** to many shell(s) and give them the alias of **"Shell Sessions"**

➡️➡️ So it's one shell but many names "aliases" based on its function.

➡️ Linux has more than one shell session:-

1. Login Shell.
2. Non-Login Shell
3. Interactive Shell.
4. Non-Interactive Shell.
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## **Login Shell 👤**:- 

➡️ The shell is considered as Login Shell when you use the shell to :-
 1. Login via a terminal (or Switching to another user).
 2. Login via SSH.

After successful login (No authentication failure.), a shell starts and a new era of execution begins.

**Login Shell Behind The Scene Sequence**

When shell starts, a group of pre-configured scripts is executed to setup the environment and those scripts are executed under the umbrella of Global Environment, the execution of these scripts is in the -behind the scene- sequence:- 


- Login Shell invokes ```
/etc/profile``` that contains global configuration that applies to all users.

- accessing its ```
/etc/profile.d/*.sh
``` directory

- In the user's home directory, ``` ~/.bash_profile 
``` file is **executed** and it's a personal initialization file for configuring the user environment to configure your shell before the initial command prompt besides ```~/.bash_login``` and ```~/.profile``` 

- ```~/.bash_profile``` is configured to invoke ``` ~/.bashrc``` that defines settings for that logged-in user.

- ``` ~/.bashrc``` calls ```/ect/.bashrc```


 _______________________________
## **Non-Login Shell 👤**:- 

➡️ The shell is considered as Non-Login Shell once the user has authenticated via terminal or via SSH and then opened **a new** terminal, that new terminal opened is considered as Non-Login Shell because user is no longer asked for login credentials.
So, a non-login shell is started by a login shell.

**Login Shell Behind The Scene Sequence**

When that non-login shell starts, a group of pre-configured scripts is executed to setup the environment,  the execution of these scripts is in the -behind the scene- sequence:- 


- Non-login shell executes ```~/.bashrc```  that defines the settings for the logged-in user (*note*: that ```~/.bashrc``` is executed after a user has successfully logged in). 

- ```~/.bashrc``` executes ```/etc/bashrc```

- ```/etc/bashrc``` invokes the scripts in ``` /etc/profile.d ```


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## **Interactive Shell 🥂 **:- 

➡️ The shell that expects you, *User*, to interact with it, *for example* the user is going to enter some inputs to the shell via keyboard. That one is considered as "Interactive Shell".

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## **Non-Interactive Shell 🍸 **:- 

 ➡️ Non-interactive concept is for systems that are not used directly by people and they don't accept user input.

 ➡️ In our Linux, Shell is considered as **Non-interactive **one when there is no interaction on behalf of the user. User is not a part of that process and shell doesn't expect any interactivity from the user.

**So, 🤔 Where interaction comes 🤔?**
that shell expects inputs to interact but *in case of* **Non-Interactive shell**, the input comes from **automated script**  and the user doesn't interact with that shell with his hand and keyboard. A script does that interaction and the output is redirected to a file.

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# Conclusion
- So i tried to cover up one of the most concepts in shell, shell sessions, to change the way how you deal and interact with your next shell(s).
- We, together, started by Login and Non-Login Shell which the shell you daily use when accessing your remote server via SSH or via terminal.
- Then we moved to Interactive & Non-Interactive Shell, The Interactive Shell that you interact with it using your keyboard*. And the one which is used by an automated script while user doesn't touch it and that is *the Non-Interactive One*
- Hola, Linux 👋 will take the road of simplifying many Linux concepts.