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functions.md

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Built-in Functions

String Functions

Function Description Example
upper(string) Convert to uppercase upper("hello") → "HELLO"
lower(string) Convert to lowercase lower("HELLO") → "hello"
trim(string, chars) Trim characters from both ends trim(" hello ", " ") → "hello"
trimspace(string) Trim whitespace trimspace(" hello ") → "hello"
replace(string, old, new) Replace substrings replace("hello", "l", "L") → "heLLo"
substr(string, offset, length) Extract substring substr("hello", 0, 2) → "he"
join(separator, list) Join list elements join(",", ["a", "b"]) → "a,b"
split(separator, string) Split string into list split(",", "a,b") → ["a", "b"]
format(spec, args...) Printf-style formatting format("Hello %s", "world")

Collection Functions

Function Description
length(collection) Return length of list, map, or string
contains(list, value) Check if list contains value
concat(list1, list2, ...) Concatenate lists
keys(map) Return map keys
values(map) Return map values
merge(map1, map2, ...) Merge maps
sort(list) Sort a list of strings
distinct(list) Remove duplicates
flatten(list) Flatten nested lists
reverse(list) Reverse a list

Numeric Functions

Function Description
abs(number) Absolute value
ceil(number) Round up
floor(number) Round down
max(numbers...) Maximum value
min(numbers...) Minimum value

Filesystem Functions

Function Description Example
file(path) Read file contents file("/etc/hostname")
template(path) Render Go template template("./config.tpl")
basename(path) Get filename from path basename("/etc/nginx/nginx.conf") → "nginx.conf"
dirname(path) Get directory from path dirname("/etc/nginx/nginx.conf") → "/etc/nginx"

Template Function

The template() function renders Go templates with access to all HCL variables and resource attributes. Templates have access to all Sprig functions, providing Helm-style templating capabilities.

Template file (env.tpl):

APP_NAME={{ .var.app_name }}
PORT={{ .var.port }}
CONFIG_DIR={{ .directory.config_dir.path }}

HCL configuration:

variable "app_name" {
  default = "myapp"
}

variable "port" {
  default = "8080"
}

resource "directory" "config_dir" {
  path = "/opt/myapp/config"
}

resource "file" "env_file" {
  path    = "${directory.config_dir.path}/env"
  content = template("./env.tpl")
}

Variables are accessible via .var.<name>, resources via .<resource_type>.<resource_name>.<attribute>, and system facts via .fact.<path> (see System Facts).

Sprig Template Functions

Templates include all Sprig functions, providing powerful templating capabilities similar to Helm.

String Functions:

{{ .var.name | upper }}                    # Convert to uppercase
{{ .var.name | lower }}                    # Convert to lowercase
{{ .var.name | title }}                    # Title case
{{ .var.text | trim }}                     # Trim whitespace
{{ .var.text | indent 4 }}                 # Indent by 4 spaces
{{ .var.text | nindent 4 }}                # Newline + indent by 4 spaces
{{ .var.list | join "," }}                 # Join list with comma

Default Values:

{{ .var.port | default 8080 }}             # Use 8080 if port is empty
{{ .var.config | default "{}" | toJson }}  # Default with JSON encoding
{{- if empty .var.optional }}
# optional not set
{{- end }}

Encoding:

{{ .var.password | b64enc }}               # Base64 encode
{{ .var.encoded | b64dec }}                # Base64 decode
{{ .var.config | toJson }}                 # Convert to JSON
{{ .var.config | toPrettyJson }}           # Pretty-print JSON
{{ .var.config | toYaml }}                 # Convert to YAML

Lists and Dicts:

{{ list "a" "b" "c" | join "," }}          # Create and join list
{{ .var.items | first }}                   # First element
{{ .var.items | last }}                    # Last element
{{ .var.items | uniq }}                    # Remove duplicates
{{ dict "key" "value" | toJson }}          # Create dictionary

Conditionals:

{{ ternary "yes" "no" .var.enabled }}      # Ternary operator
{{ .var.required | required "msg" }}       # Fail if empty

Cryptographic:

{{ .var.data | sha256sum }}                # SHA256 hash
{{ .var.password | htpasswd "user" }}      # Generate htpasswd entry

See the Sprig documentation for the complete list of available functions.

Other Functions

Function Description Example
env(name) Get environment variable env("HOME")
coalesce(values...) Return first non-null value coalesce(var.custom, "default")