WEBVTT

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In this lecture, we will take a look
at some of the common operators

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and then conditional expressions
in Terraform.

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In the previous lecture,
we saw how to test functions

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using the terraform console command.

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That's not the only use of it.

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We can also make use of arithmetic
and logical operations with Terraform

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and test the same using
the terraform console command.

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For example, we can make use of
arithmetic operations like these

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by making use of arithmetic operators.

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Besides arithmetic, Terraform
also supports equality,

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logical, and comparison operators.

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Equality operators take two values
of any data type

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and produce a Boolean result of true or false.

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To check if two values are exactly equal,

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we can make use of double equals operator
like this.

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The != operator does the inverse

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and it prints a value of true
if the two values are not equal.

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In this example, the comparison result
produces false

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as the value on the left
of the operator is a number,

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and the one on the right is a string
as it is enclosed within double quotes.

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The comparison operators of greater than,
lesser than, greater than or equal to,

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and lesser than or equal to take two values
both of type number,

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and then it produces a Boolean result.

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Let's now look at logical operators.

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The first operator is the AND operator,
which makes use of the double ampersand symbol.

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A logical AND operation
accepts two Boolean values

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and returns a true
only if both the values are true.

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For example, here 8 being greater than 7
AND 8 being less than 10 are both true.

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Hence, the result is true as well.

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If either of the values is false,
the result would be false as well.

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The logical OR operation
returns a value of true

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if either value provided to it is true.

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For example, 8 being greater than 9
OR less than 10 produces a result of true,

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since the second condition is true.

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Finally, the NOT operator returns a false
if the condition is true

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and true if the condition is false.

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For example, we have a Boolean variable here
called special with the default value of true.

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The value of var.special returns a true

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but when we use the NOT operator in front
of this variable, it results in a false.

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Another variable b has a value of 25.

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We can add a NOT operator
before the comparison b greater than 30.

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Although comparison is false,
and 25 is not greater than 30,

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we get the result of true

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as we are making use of the NOT operator
on the result of this comparison.

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The same operations can be applied
to variables in Terraform.

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If we consider a .tf file with two variables
of type number called a and b,

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we can make use of operators like this.

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That's great, but how do we make use of this
within Terraform?

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Say, we want to assign a variable to an argument
based on a condition.

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Say, if it's greater than a specific value
or another variable.

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To understand this,
let's make use of a simple example.

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Let's say we want to generate a new password.

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This can be done by making use of
the random_puzzle resource type

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from the random provider.

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This resource will generate a random password
with a user-specified length argument.

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To print the password on the screen
after a terraform apply,

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let's also make use of an output variable
called password.

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We have also defined a variable
called length of type number

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and used this within the main.tf file.

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Note that there is no default value assigned
to this variable in the variables.tf file.

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We will pass in a value for this manually
when we run the terraform apply command.

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If we run terraform apply now, a password with
the specified requirements will be printed.

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Wait, what if we want Terraform to accept a value
of length that is at least 8 characters long

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failing which use the length of 8 as default?

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With common scripting methods
such as a bash script,

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this can be done by making use of
an IF or ELSE statement like this.

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The example here has a condition,
and two statements.

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One for if the condition equals true
and the other if it is false.

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If the length variable has a value lesser than 8,
then we assign it a value of 8.

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If not, we use the length as it is.

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Once done, we can use this variable
to generate the required password.

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The same can be done in Terraform
by making use of a conditional expression.

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The syntax of using this is as follows.

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First, we have to specify the condition.

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This is followed by a question mark and a value.

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Following this, we have a colon
and another value.

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If the condition is true, the value to the right
of the question mark is considered.

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If it is false, the value to the right
of the colon is considered.

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Let's put this to use and update
our terraform configuration file

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for generating a random password
of at least 8 characters.

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The value of the length argument
can now be updated like this.

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The condition used here is to check
if the variable is lesser than 8.

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If true, use 8 as the value
of the length argument.

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Else make use of the length variable
as the value of length.

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If we run terraform init plan and apply now,
with the value of length as equal to 5,

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you can see that Terraform
still makes use of the length as 8

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and then generates the password.

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For any value greater than 8; 12, for example,

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Terraform accepts that as the value
and generates the password as expected.

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That's it for this lecture.

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Head over to the practice tests

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and practice working with functions
and conditional statements in Terraform.