Helper Functions

Boilerplate provides a rich set of helper functions available in all template files. Helper functions transform values using the pipe (|) operator.

Quick Example

Given a variable ProjectName with the value "My Cool App":

{{ .ProjectName | lower }}          → my cool app
{{ .ProjectName | snakecase }}      → my_cool_app
{{ .ProjectName | kebabcase }}      → my-cool-app
{{ .ProjectName | dasherize }}      → my-cool-app
{{ .ProjectName | camelcase }}      → MyCoolApp
{{ .ProjectName | camelCaseLower }} → myCoolApp

You can also chain multiple helpers together:

{{ .ProjectName | lower | replace " " "-" }} → my-cool-app

String Functions

Boilerplate built-in

Function	Description	Example
dasherize	Convert to dash-separated lowercase	{{ "Foo Bar" | dasherize }} → foo-bar
camelCaseLower	Lower camelCase	{{ "foo-bar" | camelCaseLower }} → fooBar
replaceOne	Replace first occurrence	{{ "aab" | replaceOne "a" "b" }} → bab

Sprig string functions

All Sprig v3 string functions are available:

Function	Description
lower	Lowercase
upper	Uppercase
title	Title Case
trim	Remove leading/trailing whitespace
trimPrefix	Remove prefix
trimSuffix	Remove suffix
replace	Replace all occurrences
contains	Check if string contains substring
hasPrefix	Check if string starts with prefix
hasSuffix	Check if string ends with suffix
snakecase	Convert to snake_case
camelcase	Convert to CamelCase
kebabcase	Convert to kebab-case
quote	Wrap in double quotes
indent	Indent each line
nindent	Indent with leading newline

Note

The older aliases downcase, upcase, capitalize, and snakeCase still work but are deprecated. Use lower, upper, title, and snakecase instead.

Math Functions

Function	Description	Example
plus	Addition	{{ plus 2 3 }} → 5
minus	Subtraction	{{ minus 10 3 }} → 7
times	Multiplication	{{ times 4 5 }} → 20
divide	Division	{{ divide 10 3 }} → 3.333...
roundInt	Round to integer	{{ roundInt 3.7 }} → 4
ceilInt	Ceiling integer	{{ ceilInt 3.2 }} → 4
floorInt	Floor integer	{{ floorInt 3.8 }} → 3
numRange	Generate number list	{{ numRange 1 5 1 }} → [1 2 3 4]

Collection Functions

Function	Description
keysSorted	Return sorted keys of a map
toYaml	Convert value to YAML string
fromYaml	Parse YAML string into a value

File & Shell Functions

Function	Description
snippet	Extract file contents, optionally by named marker
include	Include and render another template file
pathExists	Check if a file path exists
shell	Execute a shell command and capture output

snippet

Include the contents of a file, optionally extracting a named section:

{{ snippet "../src/handler.go" }}

With named sections (delimited by boilerplate-snippet: <name> comments in the source file):

{{ snippet "../src/handler.go" "main-handler" }}

include

Include and render another template file with the current variables:

{{ include "../shared/header.html" . }}

shell

Run a shell command and insert its output. This is useful for dynamically fetching values at render time — for example, looking up an AWS account ID, reading a secret, or grabbing the current git commit — and interpolating the result directly into your generated files.

Git SHA: {{ shell "git" "rev-parse" "HEAD" }}

More examples:

AWS Account ID: {{ shell "aws" "sts" "get-caller-identity" "--query" "Account" "--output" "text" }}

Current date: {{ shell "date" "+%Y-%m-%d" }}

Resolved IP: {{ shell "dig" "+short" "example.com" }}

Tip

Each argument to shell is a separate string, just like exec.Command in Go. So shell "git" "rev-parse" "HEAD" is correct, not shell "git rev-parse HEAD".

Caution

The shell helper can be disabled with --no-shell, in which case it returns the string "replace-me".

Context Functions

Function	Description
templateFolder	Absolute path to the template directory
templateUrl	The template URL as provided
outputFolder	Absolute path to the output directory
vars	Return all variables as a map
templateIsDefined	Check if a named partial/template is defined
envWithDefault	Get an environment variable with a fallback value
relPath	Create a relative path from two absolute paths

Examples

Template is at: {{ templateFolder }}
Output goes to: {{ outputFolder }}
Git branch: {{ envWithDefault "BRANCH" "main" }}

Deprecated Helpers

These older function names still work for backwards compatibility but should be replaced with their modern equivalents:

Deprecated	Use Instead
downcase	lower (Sprig)
upcase	upper (Sprig)
capitalize	title (Sprig)
snakeCase	snakecase (Sprig)
camelCase	camelcase (Sprig)
round	roundInt
ceil	ceilInt
floor	floorInt
env	envWithDefault
keys	keysSorted
replace	replaceOne or Sprig’s replace
slice	Sprig’s list

Note

The deprecated round, ceil, floor, env, keys, replace, and slice functions have different behavior than the Sprig functions with the same names. The Boilerplate-specific versions (e.g., roundInt, keysSorted) were created to avoid these conflicts.