q04-environment-variables

Énoncé§

Solve this question on: terminal

There is an existing env variable for user candidate@terminal: VARIABLE1=random-string, defined in file .bashrc. Create a new script under /opt/course/4/script.sh which:

1. Defines a new env variable VARIABLE2 with content v2, only available in the script itself
2. Outputs the content of the env variable VARIABLE2
3. Defines a new env variable VARIABLE3 with content ${VARIABLE1}-extended, available in the script itself and all child processes of the shell as well
4. Outputs the content of the env variable VARIABLE3

ℹ️ Do not alter the .bashrc file, everything needs to be done in the script itself

Solution§

Well, let’s check the existing variable and its content as mentioned:

echo $VARIABLE1
random-string
env | grep VARIABLE
VARIABLE1=random-string

How the variable’s value defined? Let’s check the .bashrc file:

cat .bashrc | grep VARIABLE1
export VARIABLE1=random-string

Now let’s create a script which will define a new env variable called VARIABLE2 with content v2:

vim /opt/course/4/script.sh
VARIABLE2="v2"
echo $VARIABLE2

We give it a try, it should output the variable content, but shouldn’t make it available (export) afterwards:

bash /opt/course/4/script.sh
v2

Finally, we define the third environment variable called VARIABLE3 within the same script

VARIABLE2=“v2”

echo $VARIABLE2

export VARIABLE3=”${VARIABLE1}-extended”    # add

echo $VARIABLE3                             # add

Run and check the result

sh /opt/course/4/script.sh
v2
random-string-extended

What’s the difference between export and not using export? Let’s demonstrate it:

TEST1=test1
export TEST2=test2
echo $TEST1
test1
echo $TEST2
test2
bash
echo $TEST1 # variable NOT available in subprocesses
echo $TEST2 # exported variable available in subprocesses
test2