Filters And Functions

All of the builtin functionalities for Tera are available.

On top of that, Sketch adds some extra filters and functions.

Functions

• uuid (generates a v4 UUID)

Filters

Strings

• capture(regex=REGEX) (matches a regex once and returns the named capture groups)
• capture_many(regex=REGEX) (matches a regex repetitively and returns the list of named capture groups)
• semver (parses a cargo-style semver and returns the segments)
• matches_semver(target=TARGET) (checks if a cargo-style semver matches a target)
• strip_prefix(prefix=PREFIX) (strips a prefix from a string, if present)
• strip_suffix(suffix=SUFFIX) (strips a suffix from a string, if present)

Filesystem

• basename (gets the basename of a directory/file)
• parent_dir (gets the parent directory of a directory/file)
• is_file (checks if a path is a file)
• is_dir (checks if a path is a directory)
• is_absolute (checks if a path is absolute)
• is_relative (checks if a path is relative)
• absolute (makes a path absolute)
• relative(from=PATH) (returns the relative path between two paths)
• read_dir (returns the list of the files contained in a directory and its subdirectories)
• glob(pattern=GLOB) (returns the glob matching entries in a directory and its subdirectories)
• matches_glob(pattern=GLOB) (checks if a path matches a glob pattern)

Serialization

• to_yaml (serializes input into yaml)
• to_toml (serializes input into prettified toml)

Examples

Template:

{# Using special variables -#}

Current arch is: {{ sketch_arch }}
Current os is: {{ sketch_os }}
Current os family is: {{ sketch_os_family }}
Is unix: {{ sketch_is_unix }}

{# Functions and filters -#}

A random uuid is: {{ uuid() }}

{# Generating a random alphanumeric string -#}
A random string is: {{ uuid() | truncate(length=6, end="") }}

{# Generating a random number -#}
A random number is: {{ get_random(start=100000, end=9999999) }}

Now is {{ now(utc=true) }}

{# Assigning an env to a variable -#}
{%- set greeting = get_env(name="GREETING") -%}

{#- Manipulating data -#}
{%- set segments = greeting | split(pat=",") -%}
First segment is: {{ segments[0] }}
Second segment is: {{ segments[1] }}

{% set some_path = "mydir/myfile" -%}
Basename is: {{ some_path | basename }}
Parent dir is: {{ some_path | parent_dir }}

{% set dir = "../sketch" -%}

{% if dir | is_dir -%}
It's a dir!
{% endif -%}

{% set file = "Cargo.toml" -%}

{% if file | is_file -%}
It's a file!
{%- endif %}

Matches glob: {{ file | matches_glob(pattern="**/*.toml") }}

{%- set captures = file | capture(regex="(?<path>.*)\.(?<extension>\w+)") %}

Path is: {{ captures['path'] }}
Extension is: {{ captures['extension'] }}

In yaml form:
{{ captures | to_yaml }}

In toml form:
{{ captures | to_toml }}

{% set words = "They're taking the hobbits to Isengard" | capture_many(regex="(?<word>[\w']+)") -%}

{% for capture in words -%}
{{ capture['word'] -}} {% if not loop.last %}{{ " " }}{% endif -%}
{%- endfor -%}!

{% set version = "v0.1.0" -%}

{% set segments = version | semver -%}
Major is: {{ segments['major'] }}
Minor is: {{ segments['minor'] }}
Patch is: {{ segments['patch'] }}

Version matches >=0.1.0: {{ version | matches_semver(target=">=0.1.0") }}
Version matches >=0.2.0: {{ version | matches_semver(target=">=0.2.0") }}

To camelCase: {{ "my_var" | camel }}
To snake_case: {{ "myVar" | snake }}
To SCREAMING_CASE: {{ "myVar" | upper_snake }}
To PascalCase: {{ "myVar" | pascal }}

Luke, I am your {{ "grandfather" | strip_prefix(prefix="grand") }}!

{% set dir = "../examples/templating/templates" -%}

{% for entry in dir | glob(pattern="example.j2") -%}
Entry: {{ entry }}
{% endfor %}

Cmd:

GREETING="hello,world" sketch render --template example.j2 --stdout

Output:

Current arch is: x86_64
Current os is: linux
Current os family is: unix
Is unix: true

A random uuid is: fd61daf5-83bf-46c6-afe3-5fcac0d6212c

A random string is: 0de4ed

A random number is: 3574820

Now is 2025-10-27T19:13:47.625250487+00:00

First segment is: hello
Second segment is: world

Basename is: myfile
Parent dir is: mydir

It's a dir!
It's a file!

Matches glob: true

Path is: Cargo
Extension is: toml

In yaml form:
path: Cargo
extension: toml


In toml form:
path = "Cargo"
extension = "toml"


They're taking the hobbits to Isengard!

Major is: 0
Minor is: 1
Patch is: 0

Version matches >=0.1.0: true
Version matches >=0.2.0: false

To camelCase: myVar
To snake_case: my_var
To SCREAMING_CASE: MY_VAR
To PascalCase: MyVar

Luke, I am your father!

Entry: example.j2