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Loop Over a Static List

Use for with a list to iterate over items and run a task or command for each one. The current item is available as {{.ITEM}}.
Taskfile.yml
version: '3'
tasks:
  image:build:
    vars:
      REPOSITORY: '{{.REPOSITORY}}'
      SRC: '{{.SRC}}'
    cmds:
      - docker build -t {{.REPOSITORY}}:latest {{.SRC}}

  build-all:
    cmds:
      - for:
          - app1
          - app2
        task: image:build
        vars:
          REPOSITORY: "{{.ITEM}}"
          SRC: "{{.ITEM}}"

  # Run different tasks based on the loop value
  task-test:
    cmds:
      - echo "Running task test"
  task-build:
    cmds:
      - echo "Running task build"
  test-start:
    cmds:
      - for: [test, build]
        task: task-{{ .ITEM }} # resolves to task-test, task-build
Demo and output
ubuntu@touted-mite:~$ task build-all
task: [image:build] docker build -t app1:latest app1
...
task: [image:build] docker build -t app2:latest app2
...

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Loop Over a Matrix

Loop over a matrix of values to combine multiple variables in each iteration.
Taskfile.yml
version: '3'
tasks:
  image:build:
    vars:
      REPOSITORY: '{{.REPOSITORY}}'
      SRC: '{{.SRC}}'
      TAG: '{{.TAG}}'
    cmds:
      - docker build -t {{.REPOSITORY}}:{{.TAG}} {{.SRC}}

  build-all:
    cmds:
      - for:
          matrix:
            REPOSITORY: [app1, app2]
            TAG: [latest, v1.0]
        task: image:build
        vars:
          REPOSITORY: "{{.ITEM.REPOSITORY}}"
          SRC: "{{.ITEM.REPOSITORY}}"
          TAG: "{{.ITEM.TAG}}"
This generates the following images:
  • app1:latest
  • app1:v1.0
  • app2:latest
  • app2:v1.0

​
Loop Over sources or generates Files

Taskfile.yml
version: '3'
tasks:
  default:
    sources:
      - foo.txt
      - bar.txt
    cmds:
      - for: sources
        cmd: cat {{ .ITEM }}

​
Loop Over Variables

Taskfile.yml
version: '3'
tasks:
  loop1: # loop over a single variable (splits on whitespace)
    vars:
      MY_VAR: hello world
    cmds:
      - for: { var: MY_VAR }
        cmd: echo {{ .ITEM }}

  loop2: # split on a custom delimiter
    vars:
      MY_VAR: hello,world
    cmds:
      - for: { var: MY_VAR, split: ','}
        cmd: echo {{ .ITEM }}

  loop3: # loop over a list variable
    vars:
      LIST: [hello, world]
    cmds:
      - for:
          var: LIST
        cmd: echo {{ .ITEM }}

  loop4: # loop over a map — KEY holds the key, ITEM the value
    vars:
      MY_MAP:
        map:
          key1: hello
          key2: world
    cmds:
      - for:
          var: MY_MAP
        cmd: echo {{.KEY}} {{ .ITEM }}

  loop5: # loop with dynamic variable from shell
    vars:
      MY_VAR:
        sh: find -type f -name '*.txt'
    cmds:
      - for: { var: MY_VAR }
        cmd: echo {{ .ITEM }}
Demo and output
ubuntu@touted-mite:~$ task loop1 loop2 loop3 loop4
task: [loop1] echo hello
hello
task: [loop1] echo world
world
task: [loop2] echo hello
hello
task: [loop2] echo world
world
task: [loop3] echo hello
hello
task: [loop3] echo world
world
task: [loop4] echo hello key1
hello key1
task: [loop4] echo world key2
world key2

​
Rename Loop Variables with as

Rename the loop variable using the as keyword for more readable commands.
Taskfile.yml
version: '3'
tasks:
  loop-rename:
    vars:
      LIST: [hello, world]
    cmds:
      - for:
          var: LIST
          as: MESSAGE
        cmd: echo {{ .MESSAGE }}

​
Loop Over Dependencies

deps run in parallel, so iterations are not guaranteed to run in order.
Taskfile.yml
version: '3'

tasks:
  default:
    deps:
      - for: [foo, bar]
        task: my-task
        vars:
          FILE: '{{.ITEM}}'

  my-task:
    cmds:
      - echo '{{.FILE}}'

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