Top 10 Templating Engines Across Major Programming Languages

In Terraform, the template process refers to the process of using a template engine to dynamically generate configuration files or values based on a set of input parameters.

Terraform supports various template engines, including Go’s text/template and html/template, as well as the Jinja2 template engine. These template engines enable you to write dynamic templates with placeholders for values that will be replaced by actual values at runtime.

The template process in Terraform involves the following steps:

1. Define a template file: Create a template file with placeholders for the values that will be replaced at runtime.
2. Define variables: Define input variables that will be used to replace the placeholders in the template file.
3. Use the template engine: Use the templatefile() function or template_file data source to render the template and generate the final output.
4. Use the output: Use the generated output in your Terraform configuration, such as passing it to a resource as a value.

The template process is useful for generating dynamic configuration files, such as cloud-init scripts, Kubernetes manifests, and shell scripts, among others. It enables you to generate configuration files based on the specific needs of your environment, without having to hard-code the values in your Terraform configuration.

Example – 1

Example 2

List 10 real use case where i can use Template template_file of Terrraform

1. Cloud-init Configuration: You can use Terraform’s template_file data source to create cloud-init configuration files for your virtual machines or instances.
2. Nginx Configuration: With template_file, you can create an Nginx configuration file to customize the web server based on your specific needs.
3. DNS Records: Use template_file to create custom DNS records and add them to your DNS server configuration files.
4. Configuration Files for Services: template_file can be used to generate configuration files for various services such as Apache, MySQL, Postgres, etc.
5. SSL/TLS Certificates: You can use template_file to generate SSL/TLS certificate configuration files for various web servers.
6. Bash Scripts: Use template_file to generate bash scripts to automate repetitive tasks such as backing up files or deploying code.
7. User Data for EC2 Instances: With template_file, you can create EC2 instance user data scripts to configure your instances when they launch.
8. Load Balancer Configuration: You can use template_file to create load balancer configuration files for services like AWS Elastic Load Balancer (ELB) or NGINX.
9. Kubernetes Manifests: template_file can be used to create Kubernetes manifest files for deploying applications to a Kubernetes cluster.
10. Database Configuration Files: Use template_file to generate database configuration files for various databases like MongoDB, Redis, Cassandra, etc.

Here is a basic 1-page tutorial for templating in Terraform using a simple Hello World example.

Basic Templating in Terraform — Hello World Tutorial

What is Templating in Terraform?

Templating in Terraform allows you to insert dynamic values into files such as:

• Configuration files
• Scripts
• YAML / JSON
• Application configs

Terraform commonly uses:

templatefile()

function to process templates.

Basic Flow of Terraform Templates

Values (variables)
        ↓
Template file (.tftpl)
        ↓
templatefile() function
        ↓
Rendered Output File
Code language: JavaScript (javascript)

Example: Hello World Template in Terraform

Goal:

Generate a file that prints:

Hello Rajesh, Welcome to Terraform Templates!

Step 1 — Create Template File

Create file:

hello.tftpl
Code language: CSS (css)

Hello ${name}, Welcome to Terraform Templates!

Here:

${name}

means:

Insert value of name variable.

Step 2 — Create Terraform File

Create file:

main.tf
Code language: CSS (css)

terraform {
  required_version = ">= 1.0"
}

# Step 1 — Define variable
variable "name" {
  default = "Rajesh"
}

# Step 2 — Generate output file using template
resource "local_file" "hello_output" {

  filename = "hello.txt"

  content = templatefile(
    "${path.module}/hello.tftpl",
    {
      name = var.name
    }
  )
}
Code language: PHP (php)

Step 3 — Initialize Terraform

terraform init

Step 4 — Apply Terraform

terraform apply

Type:

yes

Step 5 — Check Output File

Terraform will create:

hello.txt
Code language: CSS (css)

Content:

Hello Rajesh, Welcome to Terraform Templates!

Understanding Key Components

Minimal Multi-Line Template Example

Template:

hello.tftpl
Code language: CSS (css)

Hello ${name}

Environment: ${env}

Welcome to Terraform templating!

Terraform:

variable "env" {
  default = "dev"
}
Code language: JavaScript (javascript)

Output:

Hello Rajesh

Environment: dev

Welcome to Terraform templating!

Real-World Uses of Terraform Templates

Terraform templates are commonly used for:

Summary

Basic Terraform templating workflow:

1. Create template file (.tftpl)
2. Define variables
3. Use templatefile()
4. Generate output file
5. Review rendered content
Code language: CSS (css)

Core syntax:

${variable_name}

This is the basic foundation of Terraform templating, widely used in cloud-init scripts, configuration generation, and Kubernetes manifests in real DevOps projects.

Here is a 1-page basic tutorial on templating in Go with a simple Hello World example.

Basic Use of Templating in Go — Hello World Tutorial

What is Templating in Go?

Templating in Go allows you to insert dynamic values into text output such as:

• HTML pages
• Configuration files
• Logs
• YAML/JSON files

Go provides two built-in templating packages:

Basic Flow of Go Templates

Values (data)
        ↓
Template file (.tmpl)
        ↓
Interpolation {{ }}
        ↓
Rendered Output

Example: Hello World Using text/template

This example prints:

Hello Rajesh, Welcome to Go Templates!

Step 1 — Create Template File

Create file:

hello.tmpl
Code language: CSS (css)

Hello {{.Name}}, Welcome to Go Templates!

Here:

{{.Name}}

means:

Insert value of Name from data.

Step 2 — Create Go Program

Create file:

main.go
Code language: CSS (css)

package main

import (
	"os"
	"text/template"
)

// Step 1 — Define structure for values
type User struct {
	Name string
}

func main() {

	// Step 2 — Provide values
	data := User{
		Name: "Rajesh",
	}

	// Step 3 — Load template file
	tmpl := template.Must(
		template.ParseFiles("hello.tmpl"),
	)

	// Step 4 — Execute template
	tmpl.Execute(os.Stdout, data)
}
Code language: JavaScript (javascript)

Step 3 — Run the Program

go run main.go
Code language: CSS (css)

Output

Hello Rajesh, Welcome to Go Templates!

Understanding the Syntax

Example: Hello Multiple Users (List Example)

Template:

Users:

{{range .}}
Hello {{.Name}}
{{end}}

Go Code:

users := []User{
	{Name: "Rajesh"},
	{Name: "Amit"},
	{Name: "Neha"},
}

tmpl.Execute(os.Stdout, users)
Code language: JavaScript (javascript)

Output:

Users:

Hello Rajesh
Hello Amit
Hello Neha

When to Use html/template

Use html/template when generating web pages.

Example:

import "html/template"
Code language: JavaScript (javascript)

It automatically:

• Escapes HTML
• Prevents XSS attacks
• Secures web output

Real-World Uses of Go Templates

Go templates are widely used in:

Summary

Basic Go templating steps:

1. Create template file (.tmpl)
2. Provide data (struct or list)
3. Parse template
4. Execute template
5. Get output
Code language: CSS (css)

Core syntax:

{{.FieldName}}

That is the foundation of Go templating, and it is exactly the same concept used in Helm charts, Kubernetes configs, and many DevOps tools.

Rajesh Kumar

I’m a DevOps/SRE/DevSecOps/Cloud Expert passionate about sharing knowledge and experiences. I have worked at Cotocus. I share tech blog at DevOps School, travel stories at Holiday Landmark, stock market tips at Stocks Mantra, health and fitness guidance at My Medic Plus, product reviews at TrueReviewNow , and SEO strategies at Wizbrand.

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