Variables¶

What happens variables are not defined?

If the variables are not defined in the Taskfile, the configuration still remains valid, as the variables can be passed at runtime.

Taskfile.yaml

version: '3'
tasks:
  hello:
    cmds:
      - echo "Hello {{.NAME}}"

Bash

task hello NAME=KarChunT

Variable types¶

Taskfile supports several types of variables:

string
bool
int
float
array
map

Taskfile.yaml

version: '3'

vars: # global vars
  GLOBAL_VAR: "I am a global variable"

tasks:
  display-variables:
    vars:
      STRING_VAR: "Hello"
      BOOL_VAR: true
      INT_VAR: 42
      FLOAT_VAR: 3.14
      ARRAY_VAR: [1, 2, 3]
      MAP_VAR:
        map: # You can also write like this map: {A: 1, B: 2, C: 3}
          key1: value1
          key2: value2
    cmds:
      - 'echo String: {{.STRING_VAR}}'
      - 'echo Bool: {{.BOOL_VAR}}'
      - 'echo Int: {{.INT_VAR}}'
      - 'echo Float: {{.FLOAT_VAR}}'
      - 'echo Array: {{.ARRAY_VAR}}'
      - 'echo {{index .ARRAY 0}}' # 1
      - 'echo Map: {{.MAP_VAR}}'
      - 'echo Map: {{.MAP_VAR.key1}}' # display key 1 value

Set default values for variables¶

Taskfile.yaml

version: '3'
tasks:
  msg:
    vars:
      MESSAGE: '{{.MESSAGE | default "Hello World"}}'
    cmds:
      - 'echo "Message is: {{ .MESSAGE }}"'

Demo and output

ubuntu@touted-mite:~$ task msg 
task: [msg] echo "Message is: Hello World"
Message is: Hello World

# override the default value of MESSAGE
ubuntu@touted-mite:~$ task msg MESSAGE="Hi, I'm karchunt"
task: [msg] echo "Message is: Hi, I'm karchunt"
Message is: Hi, I'm karchunt

Dynamic variables / Shell command output¶

You can use sh to execute shell commands and use their output as variable values. This is useful for dynamic data retrieval, such as system information or environment variables.

Taskfile.yaml

version: '3'

tasks:
  os-version:
    vars:
      OS_VERSION:
        sh: cat /etc/os-release | grep "VERSION_ID" | cut -d "=" -f2
    cmds:
      - echo "OS version is {{.OS_VERSION}}"

Demo and output

ubuntu@touted-mite:~$ task os-version 
task: [os-version] echo "OS version is "22.04""
OS version is 22.04

Set required variables¶

You can set variables as required. If the variable is not defined, the task will not run and an error message will be displayed.

Taskfile.yaml

version: '3'
tasks:
  greet:
    requires:
      vars:
        - NAME
    cmds:
      - echo "Hello {{.NAME}}"

Demo and output

ubuntu@touted-mite:~$ task greet 
task: Task "greet" cancelled because it is missing required variables: NAME

ubuntu@touted-mite:~$ task greet NAME=KarChun
task: [greet] echo "Hello KarChun"
Hello KarChun

Ensure variables have allowed values¶

You can ensure that variables have allowed values by using the enum field. If the variable value is not in the list of allowed values, the task will not run and an error message will be displayed.

Taskfile.yaml

version: '3'
tasks:
  deploy:
    requires:
      vars:
        - name: ENV
          enum: [dev, staging, prod] # allowed values
    cmds:
      - echo "Deploy to {{.ENV}}"

Demo and output

ubuntu@touted-mite:~$ task deploy ENV=beta
task: Task "deploy" cancelled because it is missing required variables:
  - ENV has an invalid value : 'beta' (allowed values : [dev staging prod])

ubuntu@touted-mite:~$ task deploy ENV=dev
task: [deploy] echo "Deploy to dev"
Deploy to dev

Referencing other variables¶

You can reference other variables from one task to another. If you are using template engine concept, it will not able to work as expected. Here's an example.

Taskfile.yaml

version: 3

tasks:
  foo:
    vars:
      FOO: [A, B, C] # <-- FOO is defined as an array
    cmds:
      - task: bar
        vars:
          FOO: '{{.FOO}}' # <-- FOO gets converted to a string when passed to bar
  bar:
    cmds:
      - 'echo {{index .FOO 0}}' # <-- FOO is a string so the task outputs '91' which is the ASCII code for '[' instead of the expected 'A'

Demo and Output

ubuntu@touted-mite:~$ task foo
task: [bar] echo 91
91

As you can see, the output is not what we expected. So to reference variables correctly, you should use ref keyword.

Taskfile.yaml

version: 3

tasks:
  foo:
    vars:
      FOO: [A, B, C] # <-- FOO is defined as an array
    cmds: # deps ---> same concept
      - task: bar
        vars:
          FOO:
            ref: .FOO # <-- FOO gets passed by reference to bar and maintains its type
          BAR:
            ref: index .FOO 1
  bar:
    cmds:
      - 'echo {{index .FOO 0}}' # <-- FOO is still a map so the task outputs 'A' as expected
      - 'echo {{.BAR}}' # outputs 'B' as expected

The same concept applies to deps as well.

Demo and Output

ubuntu@touted-mite:~$ task foo
task: [bar] echo A
A
task: [bar] echo B
B

Parsing JSON/YAML into map variables¶

Info

This only works with ref keyword, not template engine concept.

You can parse JSON or YAML strings into map variables using the fromJson or fromYaml functions. This is useful for working with structured data.

Taskfile.yaml

version: '3'

tasks:
  task-with-map:
    vars:
      JSON: '{"a": 1, "b": 2, "c": 3}'
      FOO:
        ref: "fromJson .JSON"
    cmds:
      - echo {{.FOO}}

Demo and Output

ubuntu@touted-mite:~$ task task-with-map 
task: [task-with-map] echo map[a:1 b:2 c:3]
map[a:1 b:2 c:3]