How to Use the file Function in Terraform

In Terraform, the file function reads the contents of a file from your local system and returns it as a string. You can use it to load configuration files, scripts, or any text data into your Terraform resources or variables.

Syntax

The file function takes a single argument: the path to the file you want to read. It returns the entire content of that file as a string.

• file(path): Reads the file at path and returns its content.

terraform

file("path/to/file.txt")

Example

This example shows how to read a local script file and use its content as user data in an AWS EC2 instance resource.

terraform

variable "script_path" {
  default = "./setup.sh"
}

resource "aws_instance" "example" {
  ami           = "ami-0c55b159cbfafe1f0"
  instance_type = "t2.micro"

  user_data = file(var.script_path)

  tags = {
    Name = "ExampleInstance"
  }
}

Output

Terraform will read the contents of './setup.sh' and pass it as the user data script to the EC2 instance during creation.

Common Pitfalls

• Using a wrong or relative file path that does not exist causes Terraform to error out.
• The file function reads files only from the local machine where Terraform runs, not from remote locations.
• Trying to read binary files may cause unexpected results since file returns a string.

terraform

/* Wrong usage: file path does not exist */
user_data = file("./nonexistent.sh")

/* Correct usage: ensure file exists and path is correct */
user_data = file("./setup.sh")

Quick Reference

Tips for using file function:

• Always verify the file path is correct and accessible.
• Use file for text files like scripts, configs, or certificates.
• For binary files, consider filebase64 instead.
• Combine with variables to make file paths configurable.

Key Takeaways

The file function reads local file contents and returns them as a string.

Use file to load scripts or config files into Terraform resources or variables.

Ensure the file path is correct and the file exists to avoid errors.

file works only with local files accessible to Terraform during execution.

For binary data, use filebase64 instead of file.