Template function reference

hull’s expression engine ships ~200 built-in functions. Every function is documented with its signature and an input → output example, split into category pages so you can find what you need fast.

Pipeline convention. In ${value | f x y} the value to the left of the pipe is the function’s first argument, so it calls f(value, x, y). For example ${"hello" | upper} calls upper("hello") → "HELLO", and ${values.text | replace "old" "new"} calls replace(values.text, "old", "new").

Categories

Page	Covers
String	upper, lower, trim, replace, quote, indent, trunc, camelcase, kebabcase, snakecase, initials, …
Math & logic	add, sub, mul, div, mod, max, min, round, default, required, ternary, omitempty, …
Collection & type	keys, values, first, last, join, uniq, compact, has, toYaml, toJson, toInt, toBool, …
Date & encoding	now, date, dateInZone, toDate, ago, b64encode, b64decode, sha256, …
Crypto & secrets	sha256sum, bcrypt, genPrivateKey, genCA, randAlphaNum, uuidv4, sops, externalSecret, sealedSecret, …
Regex, path & misc	regexMatch, regexReplaceAll, base, dir, ext, urlParse, dict, merge, pick, semver, coalesce, …
Sequence, Sprig & external	until, seq, slice, dig, chunk, fromJson, http, httpJSON, vault, env, the must* variants, …

How to read an entry

### `funcName`
`funcName(value, arg) → returnType`

One-line description of what it does.

${"input" | funcName "arg"}   → output

The expression is on the left of the →, the real rendered result on the right — exactly what hull emits, not an escaped string. So toJson shows {"a":1}, never "{\"a\":1}".

• Scalars (string, number, bool) are shown as the literal value.
• Lists and maps are shown in their real serialized form, e.g. [1,2,10] or {"a":1,"b":2}.

• Multi-line results (like toYaml) are shown as the actual lines beneath a # → marker:

  ${dict "a" 1 "b" 2 | toYaml}
  # →
  a: 1
  b: 2
  

When a result varies between runs (timestamps, random keys, network responses), the example shows its shape and is marked (shape; value varies).

Building lists and maps in an example

hull has no list literal — ${[1,2,3]} renders as null. Construct a list with tuple, and a map with dict:

${tuple 10 2 1 | sortNumeric}     → [1,2,10]
${dict "a" 1 "b" 2 | keys}        → ["a","b"]

In real templates you more often pipe a list straight from your values (${values.ports | toYaml}) or from a list-producing function like split, until, or keys.

See also

• Expressions — the ${...} syntax, operators, and pipelines
• CLI reference — the commands that render these templates