Difference between local and environment variable?

Local variables and environment variables serve different purposes in a shell environment:

Local Variables

Scope: Local variables are only accessible within the shell session or script where they are defined. They cannot be accessed by child processes.
Definition: They are defined without the export command. For example:
```
local_var="This is a local variable"
```
Usage: Typically used for temporary data storage within scripts.

Environment Variables

Scope: Environment variables are accessible to all processes running in the current shell session and any child processes.
Definition: They are defined using the export command. For example:
```
export MY_VAR="This is an environment variable"
```
Usage: Commonly used to configure system settings and provide information to applications.

Example

# Local variable
local_var="Hello"
echo $local_var  # Outputs: Hello

# Environment variable
export env_var="World"
echo $env_var    # Outputs: World

# Child process accessing environment variable
bash -c 'echo $env_var'  # Outputs: World
# Child process cannot access local variable
bash -c 'echo $local_var' # Outputs nothing

In summary, local variables are limited to the current shell or script, while environment variables can be accessed by any process spawned from that shell.