exit a bash script exit 0 and exit 1 explained

## Understanding Exit Codes in Bash Scripts: A Comprehensive Guide

Bash scripts are powerful tools for automating tasks, and understanding how to control their execution flow is crucial for writing robust and reliable scripts. One of the most fundamental aspects of controlling execution is understanding *exit codes*. Exit codes are small integer values returned by a script or command that indicate its success or failure. This tutorial will delve deep into exit codes, specifically focusing on `exit 0` and `exit 1`, with plenty of code examples to solidify your understanding.

**1. What are Exit Codes?**

* **Definition:** An exit code (also known as a return code or status code) is a numerical value between 0 and 255 that a command or script returns to the operating system upon completion. It's like a "report card" telling the system how the command/script fared.

* **Purpose:** Exit codes allow programs and scripts to communicate their success or failure status to other programs, scripts, or the operating system itself. This information is critical for decision-making in automated processes.

* **Convention:** By convention:

* **0 (Zero):** Indicates successful execution. No errors were encountered, and the command/script completed as expected.
* **Non-Zero Values (1-255):** Indicate failure. Different non-zero values can be used to represent different types of errors or problems. However, the precise meaning of each non-zero code is specific to the command/script that returns it.

* **Accessing Exit Codes:** You can access the exit code of the most recently executed command in Bash using the special variable `$?`. It's important to note that `$?` is *immediately* updated after each command runs. Therefore, you must check it *immediately* after the command you are interested in.

**2. `exit` Command: The Exit Code Generator**

The `exit` command is the primary way to explicitly set the exit code of a Bash script. Its syntax is simple: ...

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