bash exit command and exit codes

## Bash Exit Command and Exit Codes: A Comprehensive Guide

This tutorial provides an in-depth exploration of the `exit` command and exit codes in Bash scripting. Understanding these concepts is crucial for writing robust and reliable shell scripts that can be easily integrated into larger systems. We will cover the following topics:

**1. What are Exit Codes?**

* Definition and Purpose
* The Range of Valid Exit Codes (0-255)
* The Significance of Exit Code 0
* Non-zero Exit Codes and Error Indication

**2. The `exit` Command**

* Syntax and Usage
* Exiting a Script at Any Point
* Exiting a Function
* Exiting a Subshell

**3. Checking Exit Codes**

* The `$?` Variable
* Using `if` Statements to Check Exit Codes
* Logical Operators (`&&` and `||`) and Exit Codes
* `set -e` and its effect on exit codes

**4. Using Exit Codes for Error Handling**

* Customizing Exit Codes
* Defining Meaningful Exit Codes
* Error Logging and Debugging

**5. Best Practices for Using Exit Codes**

* Consistency and Clarity
* Avoiding Ambiguous Exit Codes
* Documenting Exit Code Behavior

**6. Advanced Scenarios**

* Returning Exit Codes from Functions
* Using Exit Codes in Pipelines
* Handling Exit Codes in Looped Operations

Let's begin:

**1. What are Exit Codes?**

* **Definition and Purpose:**
An exit code (also known as a return code or status code) is a small integer value returned by a process (like a shell script or a command) after it completes its execution. It signals whether the process was successful or encountered an error. Think of it as a "thumbs up" or "thumbs down" indicator from the program to the operating system. The operating system and other programs can then use this code to determine what actions to take next.

* **The Range of Valid Exit Codes (0-255):**
Exit codes are typically represented as integers between 0 and 255 (inclusive). This is because they are often stored in a single byte.

* **The Signifi ...

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