Environment Variables

We talked about how you can create and use local variables in your shell:

name="Lane"
echo $name
# Lane

There is another type of variable called an environment variable. They are available to all programs that you run in your shell.

You can view all of the environment variables that are currently set in your shell with the env command.

To set a variable in your shell, use the export command:

export NAME="Lane"

You can then use the variable in your shell, just as before:

echo $NAME
# Lane

The interesting part is that programs and scripts you run in your shell can also use that variable:

For example, we can create a file called introduce.sh with the following contents:

#!/bin/sh
echo "Hi I'm $NAME"

Then we run it:

chmod +x ./introduce.sh

./introduce.sh
# Hi I'm Lane

Assignment

Take a look at the contents of the warn.sh script in the worldbanc/private/bin directory. It looks like it's supposed to print nicely formatted warning messages with worldbanc branding.

export the required environment variables:

WARN_MESSAGE: "The auditor is here"
WARN_FROM_NAME: "Your worst nightmare"

Run the script and paste its full output into the input field and submit your answer.

Tip

You can also temporarily set a variable for a single command, instead of exporting it (exporting means the variable will persist until you close the shell).

For example:

WARN_MESSAGE="this works too" ./warn.sh