Variables & templates

Stackctl has two kinds of key-value settings: vars and env. They look similar but do different things.

	vars	env
Used as	{{.NAME}} in the task file	$NAME in the shell / program
Visible to the program	No	Yes
Override from the CLI	Yes: stackctl run build APP=x	No

vars

vars:
  APP: myapp

tasks:
  build:
    cmds:
      - "go build -o bin/{{.APP}} ."

Override a variable when you run the task:

stackctl run build APP=other

Priority, from lowest to highest: global vars, task vars, command line.

env

env:
  CGO_ENABLED: "0"

tasks:
  build:
    env:
      GOOS: linux
    cmds:
      - go build .

Priority, from lowest to highest: your shell environment, global env, task env.

Values must be strings

In all three formats, vars and env values are strings. In YAML write "0" or "true", not 0 or true.

Templates

Commands use Go's text/template syntax.

Where templates are processed:

• every command (cmd and cmds)
• dir
• env values

Where they are not: vars values, task names, deps, aliases and desc.

vars:
  APP: myapp
  MODE: prod

tasks:
  build:
    cmds:
      - go build -o bin/{{.APP}} .
      - '{{if eq .MODE "prod"}}strip bin/{{.APP}}{{end}}'
      - echo "{{printf "%s-%s" .APP .MODE}}"

What you can use:

• {{.NAME}} for variables. For names with a dash, use {{index . "MY-VAR"}}.
• if, else, range, with.
• Go's built-in functions: eq, ne, lt, and, or, not, len, index, printf, print.

A missing variable renders as an empty string.

YAML quoting

A YAML value that starts with {{ must be quoted, or YAML reads it as a map.

Special variables

Variable	Value
CLI_ARGS	Everything passed after -- on the command line