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: '2'

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

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

version: '2'

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

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

version: '2'

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.

Operating System specific tasks

If you add a Taskfile_{{GOOS}}.yml you can override or amend your Taskfile based on the operating system.

Example:

Taskfile.yml:

version: '2'

tasks:
  build:
    cmds:
      - echo "default"

Taskfile_linux.yml:

version: '2'

tasks:
  build:
    cmds:
      - echo "linux"

Will print out linux and not default.

Keep in mind that the version of the files should match. Also, when redefining a task the whole task is replaced, properties of the task are not merged.

It's also possible to have an OS specific Taskvars.yml file, like Taskvars_windows.yml, Taskvars_linux.yml, or Taskvars_darwin.yml. See the variables section below.

Including other Taskfiles

This feature is still experimental and may have bugs.

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: '2'

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.

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: '2'

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

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

Task dependencies

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

version: '2'

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: '2'

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.

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

version: '2'

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: '2'

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: '2'

tasks:
  main-task:
    cmds:
      - task: write-file
        vars: {FILE: "hello.txt", CONTENT: "Hello!"}
      - task: write-file
        vars: {FILE: "world.txt", CONTENT: "World!"}

  write-file:
    cmds:
      - echo "{{.CONTENT}}" > {{.FILE}}

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

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: '2'

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 both are given, Task will compare the modification date/time of the 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.

If you prefer this check to be made by the content of the files, instead of its timestamp, just set the method property to checksum. You will probably want to ignore the .task folder in your .gitignore file (It's there that Task stores the last checksum).

version: '2'

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

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

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: '2'

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

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.

If you need a certain set of conditions to be true you can use the preconditions stanza. preconditions are very similar to status lines except they support sh expansion and they SHOULD all return 0.

version: '2'

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: '2'
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"

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)
• Variables declared in the vars: option in the Taskfile
• Variables available in the Taskvars.yml file
• Environment variables

Example of sending parameters with environment variables:

$ TASK_VARIABLE=a-value task do-something

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. Variables given in this form are only visible to the task called right before.

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

If you want to set global variables using this syntax, give it before any task:

$ task OUTPUT=file.txt generate-file

Example of locally declared vars:

version: '2'

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

Example of global vars in a Taskfile.yml:

version: '2'

vars:
  GREETING: Hello from Taskfile!

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

Example of Taskvars.yml file:

PROJECT_NAME: My Project
DEV_MODE: production
GIT_COMMIT: {sh: git log -n 1 --format=%h}

Variables expansion

Variables are expanded 2 times by default. You can change that by setting the expansions: option. Change that will be necessary if you compose many variables together:

version: '2'

expansions: 3

vars:
  FOO: foo
  BAR: bar
  BAZ: baz
  FOOBAR: "{{.FOO}}{{.BAR}}"
  FOOBARBAZ: "{{.FOOBAR}}{{.BAZ}}"

tasks:
  default:
    cmds:
      - echo "{{.FOOBARBAZ}}"

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: '2'

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.

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 sprig lib are available. The following example gets the current date in a given format:

version: '2'

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: '2'

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: '2'

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: '2'

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

      It will build your project before starting the release it.
      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 it.
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.

Silent mode

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

version: '2'

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's three ways to enable silent mode:

• At command level:

version: '2'

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

• At task level:

version: '2'

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

• Or globally with --silent or -s flag

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

version: '2'

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: '2'

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: '2'

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: '2'

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: '2'

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.

Watch tasks

If you give a --watch or -w argument, task will watch for file changes and run the task again. This requires the sources attribute to be given, so task know which files to watch.