How to modify environment variables?

To modify environment variables in a Linux environment, you can use the export command in the terminal. Here are the steps to modify an environment variable:

Open your terminal.
Check the current value of the variable (if it exists):
```
echo $VARIABLE_NAME
```
Modify the variable:
You can change the value of an existing variable or create a new one using the export command. For example, to modify an existing variable or create a new one:
```
export VARIABLE_NAME="new_value"
```
Make the change persistent (optional):
If you want the change to persist across terminal sessions, add the export command to your shell's configuration file (e.g., .bashrc for Bash or .zshrc for Zsh). Open the file in a text editor:
```
nano ~/.zshrc  # or ~/.bashrc
```
Add the export line at the end of the file:
```
export VARIABLE_NAME="new_value"
```
Save and exit the editor. In nano, you can do this by pressing Ctrl+O, Enter, and then Ctrl+X.
Apply the changes without restarting the terminal:
```
source ~/.zshrc  # or source ~/.bashrc
```
Verify the change:
```
echo $VARIABLE_NAME
```

This will show the updated value of the environment variable.