Note_Tech

All technological notes.

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Terraform - Interpolation

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• Terraform - Interpolation
  • Interpolation
    • Variables
    • Math
    • Conditional

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Interpolation

• In Terraform, it is allowed to interpolate other values using ${}

• Interpolation types:

  • Variables: ${var.variable_name}
  • Resources: ${aws_instance.name.id}
  • Data Source: ${data.template_file.name.rendered}

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Variables

Variable Type	Syntax	Example
String	var.VAR_NAME	${var.aws_region}
Map	var.MAP_NAME["key_name"]	${var.amis["us-east-1"]}/${lookup(var.amis, var.aws_region)}
List	var.LIST_NAME,var.LIST_NAME[index]	${var.subnets[i]},${join(",",var.subnets)}
Outputs of a module	module.NAME.output	${module.aws_vpc.vpcid}
Count informatnion	count.FIELD	${count.index}
Path information	path.TYPE	path.cwd(current dir), path.module(module path),path.root(root module path)
Meta information	terraform.FIELD	terraform.env(active workspace)

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Math

• ${2 + 3 * 4}

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Conditional

• Syntax:

condition ? trueval : falseval

• Example

resource "aws_instance" "myinstance"{

    count = ${var.env == "prod" ? 2 : 1}    # if the env is prod, then provision 2 instances, otherwise just 1.
}

• Operators
  • ==
  • !=
  • <, <=
  • >,>=
  • &&, ||, !