Writing your first bash script

A Bash script is a plain text file containing a series of commands written in the Bash programming language. Serving as an executable script in Unix-like environments, it automates tasks by executing commands sequentially. Bash scripts often utilize variables, conditionals, and loops to perform more complex operations, providing a powerful tool for automating routine tasks and system administration.

Bash Shell Scripting/Prerequisites

Before creating a Bash script, ensure you have access to a Unix-like environment such as Linux or macOS. A text editor like Vim, Nano, or a graphical editor is necessary for script creation. Familiarize yourself with basic Bash syntax, including shebangs (#!/bin/bash) and common commands. Understanding file permissions is crucial; use the chmod +x command to grant execution permissions to your script.

Make sure to have a working knowledge of terminal navigation and basic command-line operations. Additionally, it's beneficial to grasp variables, loops, and conditional statements for more complex scripts.

Create and run your first Bash Shell script

Open any plain text editor (e.g., Notepad, TextEdit) and start typing your commands. Remember, each line represents a separate instruction.

Essential Script Elements

  1. Shebang line: This line (starting with #!) specifies the interpreter to run the script. For bash, it's typically #!/bin/bash.
  2. Comments: Start lines with # to add explanatory notes for yourself or others reading the script.
  3. Commands: These are the core of your script. Use familiar commands like echo, ls, mkdir, cp, etc., to perform desired actions.
  4. Control flow: You can control the script's execution using conditional statements (if, else, elif), loops (for, while), and functions.

Running Your Script

  1. Save the script: Choose a descriptive filename ending with .sh (e.g., hello_world.sh).
  2. Make the script executable: Open a terminal, navigate to the script's location, and use chmod +x <filename>.sh.
  3. Run the script: Execute the script by typing its filename followed by Enter in the terminal (e.g., ./hello_world.sh).
Example:

Let's create a simple script that prints "Hello, World!" to the terminal.

#!/bin/bash echo "Hello, World!"

The first line #!/bin/bash is called a shebang. It tells the system which interpreter should be used to run the script, in this case, Bash.

The second line echo "Hello, World!" is a simple command that outputs the text "Hello, World!" to the terminal.

Save Your Script

Save your script with a .sh extension. For example, you can save it as hello_world.sh. Make sure to save it in a directory where you have permission to execute files.

Make the Script Executable

In order to execute the script, you need to make it executable. Open a terminal and navigate to the directory where you saved your script. Use the following command to make it executable:

chmod +x hello_world.sh

This command changes the file permissions to allow execution.

Run Your Script

Now, you can run your script using the following command:

./hello_world.sh

The ./ is used to specify the current directory, and hello_world.sh is the name of your script. The output "Hello, World!" should be displayed on the terminal.

That's it! You've successfully created and run your first Bash script. You can gradually explore more complex scripting by adding conditional statements, loops, and interacting with user inputs and system variables.

Tips for Beginners:
  1. Start simple! Focus on basic commands and gradually build complexity.
  2. Use meaningful variable names and comments to keep your script organized and understandable.
  3. Test your script thoroughly before relying on it for critical tasks.
  4. Don't hesitate to seek help online! Numerous resources and communities exist to support your scripting journey.

Conclusion

To create and run your first Bash script, use a text editor to write a sequence of commands, including a shebang (#!/bin/bash) as the first line. Save the file with a .sh extension, make it executable using chmod +x, and execute it with ./script.sh in the terminal, initiating the script's actions.






Related Topics
  1. Understanding Bash script structure and syntax
  2. Shebang and Script Execution permissions
  3. Writing Comments in Bash Scripts
  4. Variable Declaration and Assignment in Bash
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  2. Reading User Input in Bash
  3. String Manipulation in Bash
  4. Bash Arrays | An introduction to Bash arrays
  5. Standard Input, Standard Output, and Standard Error | Bash
  6. The Pipe '|' Operator in Bash (Advanced)
  7. Conditional Expressions in Bash
  8. Read and Write to Files with Bash
  9. Command Substitution in Bash Shell
  10. Error handling in Bash scripts
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  12. Shell Expansion | Bash