# Read and Set Shell Variables

In this tutorial, you will read common environment variables, define your own shell variable, export it to child processes, and verify that child processes inherit the value you set. Along the way you will work with `echo`, `env`, `export`, and `bash`.

These skills appear directly on the RHCSA EX200 exam — understanding the difference between a shell variable and an exported environment variable is tested both in isolation and as a prerequisite for configuring services and scripts.

::remark-box
---
kind: info
---
**Before running any commands:** click the **+** button in the terminal tab bar to open a new terminal tab. The playground history tracking activates in new sessions only. Commands run in the original tab will not register for task verification.
::

---

## What You Will Build

By the end of this tutorial, the terminal will be in this state:

laborant@rocky-01 ~$ echo $MYGREETING Hello RHCSA laborant@rocky-01 ~$ bash -c 'echo $MYGREETING' Hello RHCSA

Both the parent shell and a child shell return the value you defined — this is environment inheritance in action.

---

## Step 1: Read Three Built-in Environment Variables

The shell provides a set of variables automatically. Use `echo` to read three of them.

```bash
echo $USER

Expected output:

laborant

echo $SHELL

Expected output:

/bin/bash

echo $PATH

Expected output (similar to):

/home/laborant/.local/bin:/home/laborant/bin:/usr/local/bin:/usr/bin:/bin

Each variable name is prefixed with $ — that is the signal to the shell to substitute the variable's value before the command runs.

Step 2: List All Environment Variables with env

Now use env to display every variable currently exported to the environment.

env

You will see many lines. Look for the variables you just read:

SHELL=/bin/bash
HOME=/home/laborant
USER=laborant
PATH=/home/laborant/.local/bin:/home/laborant/bin:/usr/local/bin:/usr/bin:/bin
LANG=en_US.UTF-8

Everything shown here is inherited by any command this shell launches.

env | grep PATH

Step 3: Create a Shell Variable

Define your own variable.

MYGREETING="Hello RHCSA"

No output is produced — the shell accepts the assignment silently. Confirm the value is set:

echo $MYGREETING

Expected output:

Hello RHCSA

Step 4: Confirm the Variable Is Not Yet Inherited

Check what a child shell sees before you export MYGREETING.

bash -c 'echo $MYGREETING'

Expected output:

The output is an empty line. The child shell has no knowledge of MYGREETING because it has not been exported yet.

Step 5: Export the Variable

Mark MYGREETING for inclusion in the environment of every child process this shell launches.

export MYGREETING

Again, no output — the shell accepts the export silently.

Step 6: Verify Inheritance in a Child Process

Now that MYGREETING is exported, confirm that a child shell inherits it.

bash -c 'echo $MYGREETING'

Expected output:

Hello RHCSA

The same value you set in the parent shell is now visible inside the child shell — this is environment inheritance.

Step 7: Confirm the Complete Final State

Verify both the parent shell and a child shell return the expected value.

echo $MYGREETING

Expected output:

Hello RHCSA

bash -c 'echo $MYGREETING'

Expected output:

Hello RHCSA

Both commands return Hello RHCSA — the system is in the state described at the top of this tutorial.

What You Accomplished

In this tutorial, you:

1. Read the values of built-in environment variables $USER, $SHELL, and $PATH using echo
2. Listed all exported environment variables using env
3. Defined a new shell variable MYGREETING with an assigned value
4. Confirmed that an unexported variable is invisible to child processes
5. Exported MYGREETING using export
6. Verified that a child process launched with bash -c inherits the exported variable

Next Steps

• Persist variables across sessions — write export MYGREETING="Hello RHCSA" into ~/.bash_profile and verify it survives logout
• Unset a variable — try unset MYGREETING and confirm echo $MYGREETING returns an empty line
• Inspect a variable's export status — run declare -p MYGREETING before and after export and compare the flags shown