Update bash-9-scripting.md

docs/pages/bash/bash-9-scripting.md

@@ -13,6 +13,29 @@ echo hello # how are you? my command ls ; cd
 
 When it will come the time to write scripts, you will have to use it extensively to comment your code...
 
+## Variable
+
+A variable is a named storage location that holds a value or information. Think of a variable as a container. The name of the variable allows you to refer to and access the stored value.
+
+In bash any character or string can become a variable storing any value using the = sign as follow:
+
+```bash
+v=hello
+var=4
+echo $v
+echo $var
+```
+
+!!! question "Try to define a variable `number` and initialize it to 10. Display the value of the variable with `echo`. Change its value to 20 and display it"
+
+??? example "Click to show the solution"
+    ```bash
+    number=10
+    echo $number
+    number=20
+    echo $number
+    ```
+
 ## First script
 
 !!! question "Write a bash script called `count.sh` that allows to count the number of files contained in the directory `training_unix_basics/data`"