Expressions and Templates

Template variables and pipe filters provide in-line transformation of values inside workflow steps. No shell gymnastics needed.

Built-in variables

These variables are available in all cmd:, mcp:, run_if, and skip_if fields:

Variable	Example value	Description
{{date}}	2026-04-02	Current date (YYYY-MM-DD)
{{datetime}}	2026-04-02T14:30:00	Current date and time
{{hostname}}	web-01	Machine hostname
{{task_ref}}	backup/db-full	Current task identity
{{step_id.status}}	success	Step outcome (success, failed, skipped, timedout)
{{step_id.var}}	(captured value)	Output captured from a previous step

Step status variables are set automatically after each step completes. Captured outputs require an outputs: block on the source step (see Workflows & YAML).

Pipe filters

Chain filters after a variable using the | character:

cmd: echo "Host: {{hostname | upper}}, DB: {{db_name | default 'mydb'}}"

Available filters

Filter	Example	Result
upper	{{hostname | upper}}	MYSERVER
lower	{{name | lower}}	myname
trim	{{input | trim}}	Strips leading/trailing whitespace
default	{{db | default 'mydb'}}	Fallback if variable is empty
replace	{{path | replace '/' '-'}}	Character replacement
truncate	{{log | truncate 80}}	Limit string length
split	{{csv | split ','}}	Split string into array
first	{{list | first}}	First element of array
last	{{list | last}}	Last element of array
nth	{{list | nth 2}}	Nth element of array (zero-indexed)
count	{{list | count}}	Number of elements in array

Ternary expressions

Compare a variable and branch on the result:

cmd: echo "Deploying to {{env | eq 'prod' ? 'production' : 'staging'}}"

This evaluates the env variable: if it equals prod, the expression resolves to production; otherwise staging.

Date offsets

Generate dates relative to today:

Expression	Description
{{date_offset +7d}}	7 days from now
{{date_offset -1w}}	1 week ago
{{date_offset -1d}}	Yesterday

Date offsets are useful for log rotation, retention windows, and scheduled checks.

Docker and Go template passthrough

Syntax like {{.Names}} or {{.Status}} is left untouched by the template engine. This means Docker and Go template commands work without escaping:

cmd: docker ps --format "table {{.Names}}\t{{.Status}}"

TIP

The engine distinguishes workflow variables (lowercase, underscores) from Docker/Go templates (leading dot) automatically. No special quoting is needed.

for_each loops

Iterate over a list of values, running the step once per item. Each iteration receives {{item}} as a template variable.

Static list

steps:
  - id: backup-all
    cmd: pg_dump {{item}} > /tmp/{{item}}_backup.sql
    for_each:
      source: list
      items: [users_db, orders_db, analytics_db]
    for_each_parallel: true
    for_each_continue_on_error: true

Dynamic list from command output

steps:
  - id: restart-unhealthy
    cmd: docker restart {{item}}
    for_each:
      source: command
      command: "docker ps --filter health=unhealthy --format '{{.Names}}'"

Each line of the command's stdout becomes one item.

Options

Field	Default	Description
for_each_parallel	false	Run iterations concurrently instead of sequentially
for_each_continue_on_error	false	Continue remaining iterations if one fails

WARNING

When using for_each_parallel: true, ensure the iterated command is safe to run concurrently. Shared resources (files, ports) may cause conflicts.