129 lines
2.0 KiB
Markdown
129 lines
2.0 KiB
Markdown
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# Introduction to Bash Scripting
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Bash (Bourne Again SHell) is a command-line interface and scripting language used in Unix and Unix-like operating systems, including Linux and macOS. Bash scripts are text files containing a series of commands that can be executed by the Bash shell.
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## 1. Creating a Bash Script
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To create a Bash script:
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- Open a text editor
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- Start the file with a shebang: #!/bin/bash
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- Add your commands
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- Save the file with a .sh extension (e.g., myscript.sh)
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- Make the script executable: chmod +x myscript.sh
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Here's a simple example:
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```bash
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#!/bin/bash
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echo "Hello, World!"
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```
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## 2. Variables
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Variables in Bash are created by assigning a value:
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```bash
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name="John"
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age=30
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echo "Name: $name, Age: $age"
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```
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Use `$` to reference variables. For command substitution, use `$(command)`:
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```bash
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current_date=$(date +%Y-%m-%d)
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echo "Today is $current_date"
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```
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## 3. User Input
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Use `read` to get user input:
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```bash
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echo "What's your name?"
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read user_name
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echo "Hello, $user_name!"
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```
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## 4. Conditional Statements
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If-else statements:
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```bash
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if [ "$age" -ge 18 ]; then
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echo "You are an adult"
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else
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echo "You are a minor"
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fi
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```
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Note the spaces around the brackets and comparison operator.
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## 5. Loops
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For loop:
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```bash
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for i in {1..5}
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do
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echo "Iteration $i"
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done
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```
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While loop:
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```bash
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counter=1
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while [ $counter -le 5 ]
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do
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echo "Counter: $counter"
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((counter++))
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done
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```
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## 6. Functions
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Define and call functions:
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```bash
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greet() {
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echo "Hello, $1!"
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}
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greet "Alice"
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greet "Bob"
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```
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## 7. Command-line Arguments
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Access command-line arguments using `$1`, `$2`, etc.:
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```bash
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echo "Script name: $0"
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echo "First argument: $1"
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echo "Second argument: $2"
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echo "All arguments: $@"
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```
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## 8. File Operations
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Check if a file exists:
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```bash
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if [ -f "myfile.txt" ]; then
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echo "myfile.txt exists"
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else
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echo "myfile.txt does not exist"
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fi
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```
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Read from a file:
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```bash
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while IFS= read -r line
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do
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echo "$line"
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done < "myfile.txt"
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```
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