(ChatGPT)

Defining environment variables in a `.bat` (batch) file in Windows is straightforward. Here’s how you can define and
use environment variables within a batch file:


##################################################################################################################################
### Defining Environment Variables in a Batch File
##################################################################################################################################

1. **Create or Open a Batch File**:
   - You can create a new batch file using a text editor like Notepad. Save the file with a `.bat` extension,
     for example, `setvars.bat`.

2. **Define the Variable**:
   - Use the `set` command to define an environment variable. For example:
     ```batch
     @echo off
     set MY_VARIABLE=HelloWorld
     echo %MY_VARIABLE%
     ```

3. **Use the Variable**:
   - You can reference the variable using the `%` syntax within the same batch file.
     ```batch
     @echo off
     set MY_VARIABLE=HelloWorld
     echo %MY_VARIABLE%

     set MY_PATH=C:\MyFolder
     echo %MY_PATH%

     set MY_SCRIPT=%USERPROFILE%\scripts\myscript.py
     echo %MY_SCRIPT%
     ```

4. **PERSISTING Environment Variables**:
   - Environment variables defined using `set` are temporary and only last for the duration of the command prompt session
     or the batch file execution. If you need to set environment variables permanently, use the `setx` command.
     Note that `setx` changes the environment variable for future command prompt sessions, not the current one.
     ```batch
     @echo off
     setx MY_PERSISTENT_VARIABLE "PersistentValue"
     ```


##################################################################################################################################
### Example Batch File
##################################################################################################################################

Here’s an example batch file that sets a few environment variables and uses them:

```batch
@echo off
:: Define temporary environment variables
set MY_VARIABLE=HelloWorld
set MY_PATH=C:\MyFolder
set MY_SCRIPT=%USERPROFILE%\scripts\myscript.py

:: Display the values
echo MY_VARIABLE is %MY_VARIABLE%
echo MY_PATH is %MY_PATH%
echo MY_SCRIPT is %MY_SCRIPT%

:: Define a persistent environment variable
setx MY_PERSISTENT_VARIABLE "PersistentValue"

:: Display the persistent variable
echo MY_PERSISTENT_VARIABLE has been set to PersistentValue permanently

pause
```


##################################################################################################################################
### Running the Batch File
##################################################################################################################################

To run the batch file, simply double-click it or execute it from a command prompt:

1. **Double-Click**:
   - Navigate to the directory containing your `.bat` file and double-click it.

2. **Command Prompt**:
   - Open a command prompt (`cmd.exe`).
   - Navigate to the directory containing your `.bat` file using the `cd` command.
   - Type the name of the batch file and press Enter, for example:
     ```
     cd C:\Path\To\Your\BatchFile
     setvars.bat
     ```


##################################################################################################################################
### Notes
##################################################################################################################################

- **Temporary vs. Persistent**:
  - `set` is used for temporary variables that last for the duration of the command prompt session.
  - `setx` is used for setting persistent variables that are available in future command prompt sessions.

- **Scope**:
  - Environment variables set within a batch file using `set` are only available within that batch file and any programs it launches.

By following these steps, you can effectively define and use environment variables in your batch files,
making your scripts more flexible and powerful.