Bash = "Bourne Again SHell"

• popular Unix shell
• commonly used for scripting and automation tasks in Unix-based operating systems, including Linux and macOS.

Shebang

• he shebang, also known as a "hashbang," is the first line of a bash script and specifies the interpreter that should be used to execute the script
• typically looks like this: #!/bin/bash (indicating that Bash should be used as the interpreter)
• this line is necessary to tell the system which shell to use when executing the script.

Comments:

• bash supports comments, which are lines in the script that are not executed but serve as documentation or explanations
• comments in bash scripts start with the # symbol and can be used to provide information about the script's purpose, usage, or any other relevant details

Variables

• bash allows you to define and use variables to store and manipulate data

• variables in bash are denoted by a dollar sign ($) followed by the variable name,

  e.g. $my_variable

• you can assign values to variables using the equals sign (=), without any spaces around it, e.g. my_variable="Hello"

• bash supports both global and local variables, and you can use them to store strings, numbers, and other types of data

• Global variables

  • to define a global variable, you simply assign a value to a variable without any special syntax

    # Define a global variable
    my_global_variable="Hello, world!"
    
    # Access the global variable
    echo $my_global_variable
    

• Local variables

  • to define a local variable, you can use the **local**keyword followed by the variable name and an equals sign

    # Define a function with a local variable
    my_function() {
      local my_local_variable="Hello from function!"
      echo $my_local_variable
    }
    
    # Call the function
    my_function
    
    # Try to access the local variable outside the function (will not work)
    echo $my_local_variable
    

Control structures

• Bash provides various control structures, such as conditionals (if statements), loops (for and while loops), and case statements (case), which allow you to control the flow of your script based on conditions or iterate over lists of data
• these control structures provide powerful tools for writing dynamic and interactive bash scripts