How to Use templatefile Function in Terraform: Syntax and Example

Use the templatefile function in Terraform to read a template file and replace placeholders with variable values. It takes the file path and a map of variables, returning the rendered string for use in your configuration.

Syntax

The templatefile function requires two arguments: the path to the template file and a map of variables to replace in the template. It returns a string with all placeholders replaced by the provided values.

• templatefile(path, vars)
• path: String path to the template file.
• vars: Map of variable names and their values.

terraform

templatefile("./example.tmpl", { name = "Alice", age = 30 })

Example

This example shows how to use templatefile to render a greeting message from a template file with variables.

terraform

variable "user_name" {
  default = "Alice"
}

variable "user_age" {
  default = 30
}

output "greeting" {
  value = templatefile("./greeting.tmpl", {
    name = var.user_name,
    age  = var.user_age
  })
}

# Contents of greeting.tmpl:
# Hello, my name is ${name} and I am ${age} years old.

Output

greeting = "Hello, my name is Alice and I am 30 years old."

Common Pitfalls

Common mistakes when using templatefile include:

• Incorrect file path causing file not found errors.
• Missing variables in the map leading to unresolved placeholders.
• Using incorrect syntax inside the template file (must use ${var} format).

Always verify the template file path is correct and all variables used in the template are provided in the map.

terraform

/* Wrong: Missing variable 'age' */
output "greeting_wrong" {
  value = templatefile("./greeting.tmpl", {
    name = "Alice"
  })
}

/* Right: Provide all variables used in template */
output "greeting_right" {
  value = templatefile("./greeting.tmpl", {
    name = "Alice",
    age  = 30
  })
}

Quick Reference

Use this quick reference to remember how to use templatefile:

Feature	Description
templatefile(path, vars)	Reads a template file and replaces variables.
path	String path to the template file.
vars	Map of variable names and values for replacement.
Template syntax	Use ${var} to reference variables inside the template.
Returns	A string with variables replaced.

Key Takeaways

The templatefile function reads a file and replaces variables with values from a map.

Always provide all variables used in the template to avoid errors.

Use ${var} syntax inside the template file for placeholders.

Ensure the template file path is correct relative to your Terraform configuration.

templatefile returns a string that can be used in outputs, resources, or locals.