Getting Started with Linux Shell Scripting: A Beginner's Tutorial Linux shell scripting is a powerful tool for automating tasks, processing data and performing system maintenance. If you're new to Linux or shell scripting, this beginner's tutorial will help you get started. What is a Linux shell script? A shell script is a computer program that runs in a command-line interface. It is a series of commands and variables that are executed in a particular sequence to automate a task or to perform system maintenance. Shell scripts are written in a shell programming language like Bash, Korn, or C shell. How to create a shell script? To create a shell script, you have to follow these basic steps: 1. Open a text editor like vi, emacs, or nano. 2. Begin your script with a shebang line that specifies the shell you want to use. 3. Write your commands and save the file with a '.sh' extension. 4. Set the file as executable with the chmod command. Let's create a simple shell script that outputs "Hello, World!" on the screen. 1. Open a text editor and type: ``` #!/bin/bash echo "Hello, World!" ``` 2. Save the file with a ".sh" extension, for example, "hello_world.sh". 3. Open the terminal and navigate to the directory where you saved the file. 4. Make the script executable with the chmod command: ``` chmod +x hello_world.sh ``` 5. Run the script with the following command: ``` ./hello_world.sh ``` And you should see the output on the terminal: ``` Hello, World! ``` Variables in shell scripting Variables are used to store data that can be accessed and modified by the shell script. A variable name must start with a letter or an underscore, and it can contain letters, numbers, and underscores. To assign a value to a variable, use the equal sign (=). Let's create a shell script that uses variables to store and print some data. ``` #!/bin/bash # Assign values to variables name="John" age=30 country="USA" # Print the values echo "Name: $name" echo "Age: $age" echo "Country: $country" ``` Save the file with a ".sh" extension, for example, "data.sh". Make it executable with the chmod command, and run it with the following command: ``` ./data.sh ``` You should see the output on the terminal: ``` Name: John Age: 30 Country: USA ``` The script assigns values to three variables, name, age, and country, and prints their values using the echo command. Note that to access the value of a variable, you have to write a dollar sign ($) before the variable name. Conditional statements in shell scripting Conditional statements are used to execute different code based on a condition. In shell scripting, you can use the if-else statement to test a condition and execute different code blocks. Let's create a simple shell script that tests whether a person is eligible to vote based on their age. ``` #!/bin/bash # Assign a value to the age variable age=19 # Test the age and print a message if [ $age -ge 18 ]; then echo "You are eligible to vote." else echo "You are not eligible to vote." fi ``` Save the file with a ".sh" extension, for example, "vote.sh". Make it executable with the chmod command, and run it with the following command: ``` ./vote.sh ``` You should see the output on the terminal: ``` You are eligible to vote. ``` The script assigns a value of 19 to the age variable, tests whether the age is greater than or equal to 18 using the if statement, and prints a message accordingly. Loops in shell scripting Loops are used to execute a set of commands repeatedly. In shell scripting, you can use the while loop to execute a set of commands as long as a condition is true, or the for loop to execute a set of commands for a specified number of times. Let's create a simple shell script that prints the first ten numbers using a for loop. ``` #!/bin/bash # Print the first ten numbers for i in {1..10}; do echo $i done ``` Save the file with a ".sh" extension, for example, "numbers.sh". Make it executable with the chmod command, and run it with the following command: ``` ./numbers.sh ``` You should see the output on the terminal: ``` 1 2 3 4 5 6 7 8 9 10 ``` The script uses a for loop to iterate over the values 1 to 10 and print them using the echo command. Conclusion Linux shell scripting is a powerful tool for automating tasks, processing data, and performing system maintenance. In this beginner's tutorial, we covered some of the basic concepts of shell scripting, including creating a shell script, using variables, conditional statements, and loops. With these skills, you can start writing shell scripts to automate repetitive tasks, process large datasets, and maintain your system more efficiently.