Terraform templatefile() function renders a file as a template with variables per the Terraform docs. Use for nginx.conf, cloud-init scripts, Kubernetes manifests - any file with templated values. The team that uses templatefile() has DRY, configurable config files generated by Terraform.
Table of contents
- The templatefile function
- The template file
- Template syntax
- Loops in templates
- Conditionals
- Use cases
- Alternative: the deprecated template_file data source
- FAQ
The templatefile function
resource "local_file" "nginx_config" {
content = templatefile("${path.module}/nginx.conf.tpl", {
port = 80
upstream = "myapp:8080"
ssl_cert = "/etc/ssl/cert.pem"
})
filename = "/etc/nginx/nginx.conf"
}The team that uses templatefile() has config files generated from Terraform variables.
The template file
nginx.conf.tpl:
server {
listen ${port};
location / {
proxy_pass http://${upstream};
}
ssl_certificate ${ssl_cert};
}The ${var} syntax is Terraform template syntax. The team that writes templates has DRY config.
Template syntax
Terraform template syntax (not Jinja2):
${var}- variable substitution.$${literal}- escape dollar sign (literal${).%{ for x in list }...%{ endfor }- loops.%{ if cond }...%{ endif }- conditionals.
The team that uses these has full template power.
Loops in templates
content = templatefile("${path.module}/config.tpl", {
upstreams = ["app1:8080", "app2:8080", "app3:8080"]
})config.tpl:
%{ for upstream in upstreams ~}
upstream ${upstream} { server ${upstream}; }
%{ endfor ~}The team that uses loops has dynamic config generation.
Conditionals
%{ if ssl_enabled ~}
listen 443 ssl;
%{ else ~}
listen 80;
%{ endif ~}The team that uses conditionals has environment-specific config in one template.
Use cases
- nginx/Apache configs: virtual hosts, upstreams.
- cloud-init scripts: bootstrap scripts with EC2 metadata.
- systemd units: service files with paths and env vars.
- K8s manifests: deployment YAML with image tags.
- Bash scripts: post-install with paths.
The team that uses templates has config as code, fully managed.
Alternative: the deprecated template_file data source
Older Terraform used data "template_file". This is deprecated - use templatefile() function. The team that has old code has migration work.
FAQ
What’s the difference between templatefile() and the template_file data source?
templatefile() is the modern function (inlined). template_file data source is deprecated. The team that uses templatefile() has the current syntax.
Can I use Jinja2 syntax?
No - Terraform has its own template syntax (similar but not Jinja2). The team that uses Terraform template syntax has portable Terraform code.
How do I include a file in a template?
Use fileexists() or file() function. The team that uses file() inlines the content; templatefile() renders a template.
Can templates reference other templates?
Yes - templatefile() can be nested. The team that uses composition has modular templates.
What about YAML output?
Templates can produce any text format - YAML, JSON, INI, etc. The team that uses templates for K8s manifests has full control.
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Useful related references: