Variable scope in bash

Variable scope refers to the context in which a variable is accessible and can be referenced within a script. In Bash, variables can have different scopes depending on where they are defined.

1. Global scope: Variables defined outside of any function or block have global scope. They can be accessed from any part of the script, including within functions.

#!/bin/bash

global_var="I'm a global variable"

my_function() {
    echo "Accessing global variable: $global_var"
}

my_function

In this example, the variable global_var is defined outside of any function, making it a global variable. The my_function function is able to access and use the value of the global_var variable.

2. Local scope: Variables defined within a function have local scope. They are only accessible within the function and cannot be accessed outside of it.

#!/bin/bash

my_function() {
    local local_var="I'm a local variable"
    echo "Accessing local variable: $local_var"
}

my_function

# Attempting to access the local_var variable outside the function will result in an error
echo "Trying to access local variable outside the function: $local_var"

In this example, the variable local_var is defined inside the my_function function using the local keyword. This makes it a local variable that can only be accessed within the function. Attempting to access the local_var variable outside of the function will result in an error.

It’s important to note that when a variable is defined within a function with the same name as a global variable, the local variable takes precedence within the function. However, the global variable is still accessible outside the function.

Understanding variable scope is crucial for writing correct and maintainable Bash scripts. By properly managing the scope of variables, you can ensure that variables are accessible where needed and avoid unintended side effects or conflicts between variables.