functions

Linux/Bash Script/8-Function.md

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+# 🐚 Bash Function Syntax & Examples
+
+Bash functions allow you to group reusable logic in shell scripts. Below are clear examples and explanations to help you understand how to define and use them effectively.
+
+---
+
+## 🔧 Defining a Function
+
+You can define a Bash function in two main ways:
+
+### Option 1: Classic Syntax
+
+```bash
+function_name () {
+    # commands
+}
+```
+
+### Option 2: With the `function` Keyword
+
+```bash
+function function_name () {
+    # commands
+}
+```
+
+> 💡 Both syntaxes are valid. The use of the `function` keyword is optional and mostly stylistic.
+
+---
+
+## 📥 Passing Arguments
+
+Bash functions accept arguments just like scripts. These are accessed via `$1`, `$2`, etc.
+
+### Example: Single Argument
+
+```bash
+func1() {
+    echo "Arg: $1"
+}
+
+func1 "Test"
+```
+
+**Output:**
+
+```
+Arg: Test
+```
+
+---
+
+## ➕ Multiple Arguments & Calculation
+
+You can perform operations using passed arguments, like arithmetic:
+
+```bash
+summery() {
+    local sum=$(( $1 + $2 ))
+    echo $sum
+}
+
+summery 5 7
+```
+
+**Output:**
+
+```
+12
+```
+
+> 📌 `local` ensures `sum` is scoped within the function.
+
+---
+
+## ✅ Best Practices
+
+* Use `local` to avoid polluting the global scope.
+* Quote variables when dealing with strings.
+* Use descriptive names for clarity.
+
+---
+
+## 🧪 Try It Yourself
+
+Add these examples to a `.sh` file and run it with:
+
+```bash
+bash script.sh
+```