--- layout: page category-page: scripts category-title: Scripting tags: variables defining deleting naming author: Dario Rasic title: Script Variables previous-page: pages/scripts/0-base-commands.html next-page: pages/scripts/2-special-variables.html --- A variable is simply a string to which we assign a certain type of data, which could be a text, a number, a filename and other types of data.

Naming a variable

To name a variable in Unix we have to use only letters, numbers or the underscore character (_).
Other characters can't be used because they have a special meaning in Unix Shell.
Some simple examples are:
VAR_1
VAR_2
NAME_3
name_4

Defining a variable

To define a certain variable, we could use the following basecase:
variable_name=variable_value
Let me show you a simple example:
VAR_1=Strawberry
To access a variable we have to use the dollar sign ($). So if I want to access VAR_1, I have to write:
VAR_1="Strawberry"
echo $VAR_1
    Strawberry

Deleting a variable

Deleting a variable means that shell will remove a certain variable from the list of those that it tracks.
To delete a variable we use the following command:
unset variable_name
which in our case would be:
unset VAR_1

Protecting variables

To protect a certain variable, we can set them as read-only so that it can't be changed or deleted.
So, if we try to change the value of VAR_1, the result will be the following:
VAR_1="Strawberry"
readonly VAR_1
VAR_1="Blueberry"
    VAR_1: This variable is read only.
If we try to delete the variable, shell will give us the following value:
VAR_1="Strawberry"
unset VAR_1
    VAR_1: This variable is read only.