task/docs/usage.md

Usage

Getting started

Create a file called Taskfile.yml in the root of your project. The cmds attribute should contain the commands of a task. The example below allows compiling a Go app and uses Minify to concat and minify multiple CSS files into a single one.

version: '3'

tasks:
  build:
    cmds:
      - go build -v -i main.go

  assets:
    cmds:
      - minify -o public/style.css src/css

Running the tasks is as simple as running:

task assets build

Task uses github.com/mvdan/sh, a native Go sh interpreter. So you can write sh/bash commands and it will work even on Windows, where sh or bash are usually not available. Just remember any executable called must be available by the OS or in PATH.

If you omit a task name, "default" will be assumed.

Environment variables

Task

You can use env to set custom environment variables for a specific task:

version: '3'

tasks:
  greet:
    cmds:
      - echo $GREETING
    env:
      GREETING: Hey, there!

Additionally, you can set globally environment variables, that'll be available to all tasks:

version: '3'

env:
  GREETING: Hey, there!

tasks:
  greet:
    cmds:
      - echo $GREETING

NOTE: env supports expansion and retrieving output from a shell command just like variables, as you can see on the Variables section.

.env files

You can also ask Task to include .env like files by using the dotenv: setting:

# .env
KEYNAME=VALUE

# testing/.env
ENDPOINT=testing.com

# Taskfile.yml

version: '3'

env:
  ENV: testing

dotenv: ['.env', '{{.ENV}}/.env.', '{{.HOME}}/.env']

tasks:
  greet:
    cmds:
      - echo "Using $KEYNAME and endpoint $ENDPOINT"

Including other Taskfiles

If you want to share tasks between different projects (Taskfiles), you can use the importing mechanism to include other Taskfiles using the includes keyword:

version: '3'

includes:
  docs: ./documentation # will look for ./documentation/Taskfile.yml
  docker: ./DockerTasks.yml

The tasks described in the given Taskfiles will be available with the informed namespace. So, you'd call task docs:serve to run the serve task from documentation/Taskfile.yml or task docker:build to run the build task from the DockerTasks.yml file.

OS-specific Taskfiles

With version: '2', task automatically includes any Taskfile_{{OS}}.yml if it exists (for example: Taskfile_windows.yml, Taskfile_linux.yml or Taskfile_darwin.yml). Since this behavior was a bit too implicit, it was removed on version 3, but you still can have a similar behavior by explicitly importing these files:

version: '3'

includes:
  build: ./Taskfile_{{OS}}.yml

Directory of included Taskfile

By default, included Taskfile's tasks are ran in the current directory, even if the Taskfile is in another directory, but you can force its tasks to run in another directory by using this alternative syntax:

version: '3'

includes:
  docs:
    taskfile: ./docs/Taskfile.yml
    dir: ./docs

The included Taskfiles must be using the same schema version the main Taskfile uses.

Also, for now included Taskfiles can't include other Taskfiles. This was a deliberate decision to keep use and implementation simple. If you disagree, open an GitHub issue and explain your use case. =)

Task directory

By default, tasks will be executed in the directory where the Taskfile is located. But you can easily make the task run in another folder informing dir:

version: '3'

tasks:
  serve:
    dir: public/www
    cmds:
      # run http server
      - caddy

If the directory doesn't exist, task creates it.

Task dependencies

Dependencies run in parallel, so dependencies of a task shouldn't depend one another. If you want to force tasks to run serially take a look at the Calling Another Task section below.

You may have tasks that depend on others. Just pointing them on deps will make them run automatically before running the parent task:

version: '3'

tasks:
  build:
    deps: [assets]
    cmds:
      - go build -v -i main.go

  assets:
    cmds:
      - minify -o public/style.css src/css

In the above example, assets will always run right before build if you run task build.

A task can have only dependencies and no commands to group tasks together:

version: '3'

tasks:
  assets:
    deps: [js, css]

  js:
    cmds:
      - minify -o public/script.js src/js

  css:
    cmds:
      - minify -o public/style.css src/css

If there is more than one dependency, they always run in parallel for better performance.

You can also make the tasks given by the command line run in parallel by using the --parallel flag (alias -p). Example: task --parallel js css.

If you want to pass information to dependencies, you can do that the same manner as you would to call another task:

version: '3'

tasks:
  default:
    deps:
      - task: echo_sth
        vars: {TEXT: "before 1"}
      - task: echo_sth
        vars: {TEXT: "before 2"}
    cmds:
      - echo "after"

  echo_sth:
    cmds:
      - echo {{.TEXT}}

Calling another task

When a task has many dependencies, they are executed concurrently. This will often result in a faster build pipeline. But in some situations you may need to call other tasks serially. In this case, just use the following syntax:

version: '3'

tasks:
  main-task:
    cmds:
      - task: task-to-be-called
      - task: another-task
      - echo "Both done"

  task-to-be-called:
    cmds:
      - echo "Task to be called"

  another-task:
    cmds:
      - echo "Another task"

Overriding variables in the called task is as simple as informing vars attribute:

version: '3'

tasks:
  greet:
    vars:
      RECIPIENT: '{{default "World" .RECIPIENT}}'
    cmds:
      - echo "Hello, {{.RECIPIENT}}!"

  greet-pessimistically:
    cmds:
      - task: greet
        vars: {RECIPIENT: "Cruel World"}

The above syntax is also supported in deps.

NOTE: If you want to call a task declared in the root Taskfile from within an included Taskfile, add a leading : like this: task: :task-name.

Prevent unnecessary work

By fingerprinting locally generated files and their sources

If a task generates something, you can inform Task the source and generated files, so Task will prevent to run them if not necessary.

version: '3'

tasks:
  build:
    deps: [js, css]
    cmds:
      - go build -v -i main.go

  js:
    cmds:
      - minify -o public/script.js src/js
    sources:
      - src/js/**/*.js
    generates:
      - public/script.js

  css:
    cmds:
      - minify -o public/style.css src/css
    sources:
      - src/css/**/*.css
    generates:
      - public/style.css

sources and generates can be files or file patterns. When given, Task will compare the checksum of the source files to determine if it's necessary to run the task. If not, it will just print a message like Task "js" is up to date. You will probably want to ignore the .task folder in your .gitignore file (It's there that Task stores the last checksum).

If you prefer this check to be made by the modification timestamp of the files, instead of its checksum (content), just set the method property to timestamp.

version: '3'

tasks:
  build:
    cmds:
      - go build .
    sources:
      - ./*.go
    generates:
      - app{{exeExt}}
    method: checksum

TIP: method none skips any validation and always run the task.

NOTE: for the checksum (default) method to work, it's only necessary to inform the source files, but if you want to use the timestamp method, you also need to inform the generated files with generates.

Using programmatic checks to indicate a task is up to date.

Alternatively, you can inform a sequence of tests as status. If no error is returned (exit status 0), the task is considered up-to-date:

version: '3'

tasks:
  generate-files:
    cmds:
      - mkdir directory
      - touch directory/file1.txt
      - touch directory/file2.txt
    # test existence of files
    status:
      - test -d directory
      - test -f directory/file1.txt
      - test -f directory/file2.txt

Normally, you would use sources in combination with generates - but for tasks that generate remote artifacts (Docker images, deploys, CD releases) the checksum source and timestamps require either access to the artifact or for an out-of-band refresh of the .checksum fingerprint file.

Two special variables {{.CHECKSUM}} and {{.TIMESTAMP}} are available for interpolation within status commands, depending on the method assigned to fingerprint the sources. Only source globs are fingerprinted.

Note that the {{.TIMESTAMP}} variable is a "live" Go time.Time struct, and can be formatted using any of the methods that time.Time responds to.

See the Go Time documentation for more information.

You can use --force or -f if you want to force a task to run even when up-to-date.

Also, task --status [tasks]... will exit with a non-zero exit code if any of the tasks are not up-to-date.

Using programmatic checks to cancel execution of an task and it's dependencies

In addition to status checks, there are also preconditions checks, which are the logical inverse of status checks. That is, if you need a certain set of conditions to be true you can use the preconditions stanza. preconditions are similar to status lines except they support sh expansion and they SHOULD all return 0.

version: '3'

tasks:
  generate-files:
    cmds:
      - mkdir directory
      - touch directory/file1.txt
      - touch directory/file2.txt
    # test existence of files
    preconditions:
      - test -f .env
      - sh: "[ 1 = 0 ]"
        msg: "One doesn't equal Zero, Halting"

Preconditions can set specific failure messages that can tell a user what steps to take using the msg field.

If a task has a dependency on a sub-task with a precondition, and that precondition is not met - the calling task will fail. Note that a task executed with a failing precondition will not run unless --force is given.

Unlike status which will skip a task if it is up to date, and continue executing tasks that depend on it, a precondition will fail a task, along with any other tasks that depend on it.

version: '3'

tasks:
  task-will-fail:
    preconditions:
      - sh: "exit 1"

  task-will-also-fail:
    deps:
      - task-will-fail

  task-will-still-fail:
    cmds:
      - task: task-will-fail
      - echo "I will not run"

Limiting when tasks run

If a task executed by multiple cmds or multiple deps you can limit how many times it is executed using run. run can also be set at the root of the Taskfile to change the behavior of all the tasks unless explicitly overridden

Supported values for run

• always (default) always attempt to invoke the task regardless of the number of previous executions
• once only invoke this task once regardless of the number of references
• when_changed only invokes the task once for each unique set of variables passed into the task

version: '3.7'
tasks:
  default:
    cmds:
      - task: generate-file
        vars: { CONTENT: '1' }
      - task: generate-file
        vars: { CONTENT: '2' }
      - task: generate-file
        vars: { CONTENT: '2' }

  generate-file:
    run: when_changed
    deps:
      - install-deps
    cmds:
      - echo {{.CONTENT}}

  install-deps:
    run: once
    cmds:
      - sleep 5 # long operation like installing packages

Variables

When doing interpolation of variables, Task will look for the below. They are listed below in order of importance (e.g. most important first):

• Variables declared in the task definition
• Variables given while calling a task from another (See Calling another task above)
• Global variables (those declared in the vars: option in the Taskfile)
• Environment variables

Example of sending parameters with environment variables:

$ TASK_VARIABLE=a-value task do-something

TIP: A special variable .TASK is always available containing the task name.

Since some shells don't support above syntax to set environment variables (Windows) tasks also accepts a similar style when not in the beginning of the command.

$ task write-file FILE=file.txt "CONTENT=Hello, World!" print "MESSAGE=All done!"

Example of locally declared vars:

version: '3'

tasks:
  print-var:
    cmds:
      - echo "{{.VAR}}"
    vars:
      VAR: Hello!

Example of global vars in a Taskfile.yml:

version: '3'

vars:
  GREETING: Hello from Taskfile!

tasks:
  greet:
    cmds:
      - echo "{{.GREETING}}"

Dynamic variables

The below syntax (sh: prop in a variable) is considered a dynamic variable. The value will be treated as a command and the output assigned. If there is one or more trailing newlines, the last newline will be trimmed.

version: '3'

tasks:
  build:
    cmds:
      - go build -ldflags="-X main.Version={{.GIT_COMMIT}}" main.go
    vars:
      GIT_COMMIT:
        sh: git log -n 1 --format=%h

This works for all types of variables.

Forwarding CLI arguments to commands

If -- is given in the CLI, all following paramaters are added to a special .CLI_ARGS variable. This is useful to forward arguments to another command.

The below example will run yarn install.

$ task yarn -- install

version: '3'

tasks:
  yarn:
    cmds:
      - yarn {{.CLI_ARGS}}

Go's template engine

Task parse commands as Go's template engine before executing them. Variables are accessible through dot syntax (.VARNAME).

All functions by the Go's slim-sprig lib are available. The following example gets the current date in a given format:

version: '3'

tasks:
  print-date:
    cmds:
      - echo {{now | date "2006-01-02"}}

Task also adds the following functions:

• OS: Returns operating system. Possible values are "windows", "linux", "darwin" (macOS) and "freebsd".
• ARCH: return the architecture Task was compiled to: "386", "amd64", "arm" or "s390x".
• splitLines: Splits Unix (\n) and Windows (\r\n) styled newlines.
• catLines: Replaces Unix (\n) and Windows (\r\n) styled newlines with a space.
• toSlash: Does nothing on Unix, but on Windows converts a string from \ path format to /.
• fromSlash: Opposite of toSlash. Does nothing on Unix, but on Windows converts a string from \ path format to /.
• exeExt: Returns the right executable extension for the current OS (".exe" for Windows, "" for others).

Example:

version: '3'

tasks:
  print-os:
    cmds:
      - echo '{{OS}} {{ARCH}}'
      - echo '{{if eq OS "windows"}}windows-command{{else}}unix-command{{end}}'
      # This will be path/to/file on Unix but path\to\file on Windows
      - echo '{{fromSlash "path/to/file"}}'
  enumerated-file:
    vars:
      CONTENT: |
        foo
        bar        
    cmds:
      - |
        cat << EOF > output.txt
        {{range $i, $line := .CONTENT | splitLines -}}
        {{printf "%3d" $i}}: {{$line}}
        {{end}}EOF        

Help

Running task --list (or task -l) lists all tasks with a description. The following Taskfile:

version: '3'

tasks:
  build:
    desc: Build the go binary.
    cmds:
      - go build -v -i main.go

  test:
    desc: Run all the go tests.
    cmds:
      - go test -race ./...

  js:
    cmds:
      - minify -o public/script.js src/js

  css:
    cmds:
      - minify -o public/style.css src/css

would print the following output:

* build:   Build the go binary.
* test:    Run all the go tests.

Display summary of task

Running task --summary task-name will show a summary of a task. The following Taskfile:

version: '3'

tasks:
  release:
    deps: [build]
    summary: |
      Release your project to github

      It will build your project before starting the release.
      Please make sure that you have set GITHUB_TOKEN before starting.      
    cmds:
      - your-release-tool

  build:
    cmds:
      - your-build-tool

with running task --summary release would print the following output:

task: release

Release your project to github

It will build your project before starting the release.
Please make sure that you have set GITHUB_TOKEN before starting.

dependencies:
 - build

commands:
 - your-release-tool

If a summary is missing, the description will be printed. If the task does not have a summary or a description, a warning is printed.

Please note: showing the summary will not execute the command.

Overriding task name

Sometimes you may want to override the task name print on summary, up-to-date messages to STDOUT, etc. In this case you can just set label:, which can also be interpolated with variables:

version: '3'

tasks:
  default:
    - task: print
      vars:
        MESSAGE: hello
    - task: print
      vars:
        MESSAGE: world

  print:
    label: 'print-{{.MESSAGE}}'
    cmds:
      - echo "{{.MESSAGE}}"

Silent mode

Silent mode disables echoing of commands before Task runs it. For the following Taskfile:

version: '3'

tasks:
  echo:
    cmds:
      - echo "Print something"

Normally this will be print:

echo "Print something"
Print something

With silent mode on, the below will be print instead:

Print something

There are four ways to enable silent mode:

• At command level:

version: '3'

tasks:
  echo:
    cmds:
      - cmd: echo "Print something"
        silent: true

• At task level:

version: '3'

tasks:
  echo:
    cmds:
      - echo "Print something"
    silent: true

• Globally at Taskfile level:

version: '3'

silent: true

tasks:
  echo:
    cmds:
      - echo "Print something"

• Or globally with --silent or -s flag

If you want to suppress STDOUT instead, just redirect a command to /dev/null:

version: '3'

tasks:
  echo:
    cmds:
      - echo "This will print nothing" > /dev/null

Dry run mode

Dry run mode (--dry) compiles and steps through each task, printing the commands that would be run without executing them. This is useful for debugging your Taskfiles.

Ignore errors

You have the option to ignore errors during command execution. Given the following Taskfile:

version: '3'

tasks:
  echo:
    cmds:
      - exit 1
      - echo "Hello World"

Task will abort the execution after running exit 1 because the status code 1 stands for EXIT_FAILURE. However it is possible to continue with execution using ignore_error:

version: '3'

tasks:
  echo:
    cmds:
      - cmd: exit 1
        ignore_error: true
      - echo "Hello World"

ignore_error can also be set for a task, which mean errors will be suppressed for all commands. But keep in mind this option won't propagate to other tasks called either by deps or cmds!

Output syntax

By default, Task just redirect the STDOUT and STDERR of the running commands to the shell in real time. This is good for having live feedback for log printed by commands, but the output can become messy if you have multiple commands running at the same time and printing lots of stuff.

To make this more customizable, there are currently three different output options you can choose:

• interleaved (default)
• group
• prefixed

To choose another one, just set it to root in the Taskfile:

version: '3'

output: 'group'

tasks:
  # ...

The group output will print the entire output of a command once, after it finishes, so you won't have live feedback for commands that take a long time to run.

The prefix output will prefix every line printed by a command with [task-name] as the prefix, but you can customize the prefix for a command with the prefix: attribute:

version: '3'

output: prefixed

tasks:
 default:
   deps:
     - task: print
       vars: {TEXT: foo}
     - task: print
       vars: {TEXT: bar}
     - task: print
       vars: {TEXT: baz}

 print:
   cmds:
     - echo "{{.TEXT}}"
   prefix: "print-{{.TEXT}}"
   silent: true

$ task default
[print-foo] foo
[print-bar] bar
[print-baz] baz

The output option can also be specified by the --output or -o flags.

Short task syntax

Starting on Task v3, you can now write tasks with a shorter syntax if they have the default settings (e.g. no custom env:, vars:, desc:, silent: , etc):

version: '3'

tasks:
  build: go build -v -o ./app{{exeExt}} .

  run:
    - task: build
    - ./app{{exeExt}} -h localhost -p 8080

Watch tasks

With the flags --watch or -w task will watch for file changes and run the task again. This requires the sources attribute to be given, so task knows which files to watch.