默认情况，task 在本地项目的 `.task` 目录保存 checksums 值。 一般都会在 `.gitignore`（或类似配置）中忽略掉这个目录，这样它就不会被提交。 (If you have a task for code generation that is committed it may make sense to commit the checksum of that task as well, though).
Each task has only one checksum stored for its `sources`. If you want to distinguish a task by any of its input variables, you can add those variables as part of the task's label, and it will be considered a different task.
This is useful if you want to run a task once for each distinct set of inputs until the sources actually change. For example, if the sources depend on the value of a variable, or you if you want the task to rerun if some arguments change even if the source has not.
For the `checksum` (default) or `timestamp` method to work, it is only necessary to inform the source files. When the `timestamp` method is used, the last time of the running the task is considered as a generate.
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:
```yaml
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.
Also, `task --status [tasks]...` will exit with a non-zero exit code if any of the tasks are not up-to-date.
`status` can be combined with the [fingerprinting](#by-fingerprinting-locally-generated-files-and-their-sources) to have a task run if either the the source/generated artifacts changes, or the programmatic check fails:
```yaml
version: '3'
tasks:
build:prod:
desc: Build for production usage.
cmds:
- composer install
# Run this task if source files changes.
sources:
- composer.json
- composer.lock
generates:
- ./vendor/composer/installed.json
- ./vendor/autoload.php
# But also run the task if the last build was not a production build.
In addition to `status` checks, `preconditions` checks 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.
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.
If a task executed by multiple `cmds` or multiple `deps` you can control when 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.
A special variable `.TASK` is always available containing the task name.
:::
Since some shells do not support the above syntax to set environment variables (Windows) tasks also accept a similar style when not at the beginning of the command.
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 are one or more trailing newlines, the last newline will be trimmed.
```yaml
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.
## 将 CLI 参数转发到 cmds
If `--` is given in the CLI, all following parameters are added to a special `.CLI_ARGS` variable. This is useful to forward arguments to another command.
With the `defer` keyword, it's possible to schedule cleanup to be run once the task finishes. The difference with just putting it as the last command is that this command will run even when the task fails.
In the example below, `rm -rf tmpdir/` will run even if the third command fails:
Due to the nature of how the [Go's own `defer` work](https://go.dev/tour/flowcontrol/13), the deferred commands are executed in the reverse order if you schedule multiple of them.
All functions by the Go's [slim-sprig lib](https://go-task.github.io/slim-sprig/) are available. The following example gets the current date in a given format:
-`OS`: Returns the 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).
-`shellQuote`: Quotes a string to make it safe for use in shell scripts. Task uses [this Go function](https://pkg.go.dev/mvdan.cc/sh/v3@v3.4.0/syntax#Quote) for this. The Bash dialect is assumed.
-`splitArgs`: Splits a string as if it were a command's arguments. Task uses [this Go function](https://pkg.go.dev/mvdan.cc/sh/v3@v3.4.0/shell#Fields)
Example:
```yaml
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
Sometimes you may want to override the task name printed on the summary, up-to-date messages to STDOUT, etc. In this case, you can just set `label:`, which can also be interpolated with variables:
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.
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`:
```yaml
version: '3'
tasks:
echo:
cmds:
- cmd: exit 1
ignore_error: true
- echo "Hello World"
```
`ignore_error` can also be set for a task, which means errors will be suppressed for all commands. Nevertheless, keep in mind that this option will not propagate to other tasks called either by `deps` or `cmds`!
## 输出语法
By default, Task just redirects the STDOUT and STDERR of the running commands to the shell in real-time. This is good for having live feedback for logging printed by commands, but the output can become messy if you have multiple commands running simultaneously and printing lots of stuff.
When using the `group` output, you can optionally provide a templated message to print at the start and end of the group. This can be useful for instructing CI systems to group all of the output for a given task, such as with [GitHub Actions' `::group::` command](https://docs.github.com/en/actions/learn-github-actions/workflow-commands-for-github-actions#grouping-log-lines) or [Azure Pipelines](https://docs.microsoft.com/en-us/azure/devops/pipelines/scripts/logging-commands?expand=1&view=azure-devops&tabs=bash#formatting-commands).
```yaml
version: '3'
output:
group:
begin: '::group::{{.TASK}}'
end: '::endgroup::'
tasks:
default:
cmds:
- echo 'Hello, World!'
silent: true
```
```bash
$ task default
::group::default
Hello, World!
::endgroup::
```
When using the `group` output, you may swallow the output of the executed command on standard output and standard error if it does not fail (zero exit code).
```yaml
version: '3'
silent: true
output:
group:
error_only: true
tasks:
passes: echo 'output-of-passes'
errors: echo 'output-of-errors' && exit 1
```
```bash
$ task passes
$ task errors
output-of-errors
task: Failed to run task "errors": exit status 1
```
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:
The `output` option can also be specified by the `--output` or `-o` flags.
:::
## 交互式 CLI 应用
When running interactive CLI applications inside Task they can sometimes behave weirdly, especially when the [output mode](#output-syntax) is set to something other than `interleaved` (the default), or when interactive apps are run in parallel with other tasks.
The `interactive: true` tells Task this is an interactive application and Task will try to optimize for it:
```yaml
version: '3'
tasks:
default:
cmds:
- vim my-file.txt
interactive: true
```
If you still have problems running an interactive app through Task, please open an issue about it.
## 短 Task 语法
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):
```yaml
version: '3'
tasks:
build: go build -v -o ./app{{exeExt}} .
run:
- task: build
- ./app{{exeExt}} -h localhost -p 8080
```
## `set` 和 `shopt`
It's possible to specify options to the [`set`](https://www.gnu.org/software/bash/manual/html_node/The-Set-Builtin.html) and [`shopt`](https://www.gnu.org/software/bash/manual/html_node/The-Shopt-Builtin.html) builtins. This can be added at global, task or command level.
```yaml
version: '3'
set: [pipefail]
shopt: [globstar]
tasks:
# `globstar` required for double star globs to work
default: echo **/*.go
```
:::info
Keep in mind that not all options are available in the [shell interpreter library](https://github.com/mvdan/sh) that Task uses.
:::
## 观察任务
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.
The default watch interval is 5 seconds, but it's possible to change it by either setting `interval: '500ms'` in the root of the Taskfile passing it as an argument like `--interval=500ms`.
