WEBVTT

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In this lecture, we will see
how to make use of variables

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in Terraform.

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We have used several arguments
in our Terraform blocks so far.

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For the local file, we have
a filename and content.

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For the random pet resource, we
have used the prefix, separator,

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and length as the arguments.

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Since these values
are directly defined

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within the main configuration files,

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they are considered
to be hardcoded values.

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Hardcoding values
is not a good idea.

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For one, this limits the
reusability of the code,

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which defeats the
purpose of using IAC.

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We want to make sure that the
same code can be used again and again

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to deploy resources based
on a set of input variables

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that can be provided
during the execution.

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That is where input variables
come in to the picture.

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Just as in any general-purpose
programming language,

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such as Bash Scripting
or PowerShell,

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we can make use of input
variables in Terraform.

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To assign variables, let us
create a new configuration file

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called variables.tf and
define the values like this.

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The variables.tf file,
just like the main.tf file,

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consists of blocks
and arguments.

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To create a variable, use
the keyword called variable.

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This is followed by
the variable name.

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This can be named anything
but as a standard,

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use an appropriate name,
such as the argument name

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for which we are using the variable.

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Within this block, we can provide
a default value for the variable.

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This is an optional parameter,
but it is a quick and simple way

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to assign values
to the variables.

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We will see the other methods
to do so in a later lecture.

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Great. Now we have our
variable configuration file,

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but how do we use it
within the main.tf file?

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To do this, we can replace
the argument values

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with the variable names
prefixed with a var like this.

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When using variables, you do
not have to enclose the values

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inside double quotes as you
would when providing actual values.

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Using the same execution flow
that we have seen many times by now,

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we can create the
resources using Terraform

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plan followed by the Terraform apply.

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The resources have now
been created as expected.

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Now, if you want to make an
update to the resources

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by making changes to the
existing arguments,

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we can do that by just
updating the variables.tf file.

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The main.tf may not be modified.

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For example, let us update
the local file resource

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to create the file at the same
location but with an updated content

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that reads, "My favorite
pet is Mrs. hiskers",

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and for the random pet resource,
let's change the length

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of the pet name to two.

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We can do that like this.

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As expected, when we
run Terraform apply,

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it will recreate the resources.

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The content of the file has been
changed and the pet name now

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has two words following the prefix.

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Before we conclude this lecture,

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here is an example of what our
configuration files would look like

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when creating an EC2
instance in AWS with Terraform

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while making use
of input variables.

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Don't worry if the resource block
and the arguments are unfamiliar.

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We have a separate lecture

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where we will be making use of
AWS resources later in the course.