inv[oke] core usage

See also

This page documents invoke’s core arguments, options and behavior (which includes options present in custom Invoke-based binaries). For details on invoking user-specified tasks and other parser-related details, see Invoking tasks.

Core options and flags

invoke’s usage looks like:

$ inv[oke] [--core-opts] task1 [--task1-opts] ... taskN [--taskN-opts]

All core options & flags are below; almost all of them must be given before any task names, with a few (such as --help) being specially looked for anywhere in the command line. (For parsing details, see Basic command line layout.)

--complete

Print (line-separated) valid tab-completion options for an Invoke command line given as the ‘remainder’ (i.e. after a --). Used for building shell completion scripts.

For example, when the local tasks tree contains tasks named foo and bar, and when foo takes flags --foo-arg and --foo-arg-2, you might use it like this:

# Empty input: just task names
$ inv --complete --
foo
bar

# Input not ending with a dash: task names still
$ inv --complete -- foo --foo-arg
foo
bar

# Input ending with a dash: current context's flag names
$ inv --complete -- foo -
--foo-arg
--foo-arg-2

For more details on how to make best use of this option, see --print-completion-script.

--hide=STRING

Set default value of run()’s ‘hide’ kwarg.

--no-dedupe

Disable task deduplication.

--print-completion-script=SHELL

Print a completion script for desired SHELL (e.g. bash, zsh, etc). This can be sourced into the current session in order to enjoy tab-completion for tasks and options.

These scripts are bundled with Invoke’s distributed codebase, and internally make use of --complete.

--prompt-for-sudo-password

Prompt at the start of the session (before executing any tasks) for the sudo.password configuration value. This allows users who don’t want to keep sensitive material in the config system or their shell environment to rely on user input, without otherwise interrupting the flow of the program.

--write-pyc

By default, Invoke disables bytecode caching as it can cause hard-to-debug problems with task files and (for the kinds of things Invoke is typically used for) offers no noticeable speed benefit. If you really want your .pyc files back, give this option.

-c STRING, --collection=STRING

Specify collection name to load.

-d, --debug

Enable debug output.

--dry

Echo commands instead of actually running them; specifically, causes any run calls to:

  • Act as if the echo option has been turned on, printing the command-to-be-run to stdout;
  • Skip actual subprocess invocation (returning before any of that machinery starts running);
  • Return a dummy Result object with ‘blank’ values (empty stdout/err strings, 0 exit code, etc).
-D, --list-depth=INT

Limit --list display to the specified number of levels, e.g. --list-depth 1 to show only top-level tasks and namespaces.

If an argument is given to --list, then this depth is relative; so --list build --list-depth 1 shows everything at the top level of the build subtree.

Default behavior if this is not given is to show all levels of the entire task tree.

-e, --echo

Echo executed commands before running.

-f, --config

Specify a runtime configuration file to load.

Note that you may instead use the INVOKE_RUNTIME_CONFIG environment variable in place of this option. If both are given, the CLI option will win out.

-F, --list-format=STRING

Change the format used to display the output of --list; may be one of:

  • flat (the default): single, flat vertical list with dotted task names.

  • nested: a nested (4-space indented) vertical list, where each level implicitly includes its parent (with leading dots as a strong visual clue that these are still subcollection tasks.)

  • json: intended for consumption by scripts or other programs, this format emits JSON representing the task tree, with each ‘node’ in the tree (the outermost document being the root node, and thus a JSON object) consisting of the following keys:

    • name: String name of collection; for the root collection this is typically the module name, so unless you’re supplying alternate collection name to the load process, it’s usually "tasks" (from tasks.py.)
    • help: First line of collection’s docstring, if it came from a module; null otherwise (or if module lacked a docstring.)
    • tasks: Immediate children of this collection; an array of objects of the following form:
      • name: Task’s local name within its collection (i.e. not the full dotted path you might see with the flat format; reconstructing that path is left up to the consumer.)
      • help: First line of task’s docstring, or null if it had none.
      • aliases: An array of string aliases for this task.
    • default: String naming which task within this collection, if any, is the default task. Is null if no task is the default.
    • collections: An array of any sub-collections within this collection, members of which which will have the same structure as this outermost document, recursively.

    The JSON emitted is not pretty-printed, but does end with a trailing newline.

-h STRING, --help=STRING

When given without any task names, displays core help; when given with a task name (may come before or after the task name) displays help for that particular task.

-l, --list=STRING

List available tasks. Shows all tasks by default; may give an explicit namespace to ‘root’ the displayed task tree to only that namespace. (This argument may contain periods, as with task names, so it’s possible to show only a small, deep portion of the overall tree if desired.)

-p, --pty

Use a pty when executing shell commands.

-r STRING, --search-root=STRING

Change root directory used for finding task modules.

-T INT, --command-timeout=INT

Set a default command execution timeout of INT seconds. Maps to the timeouts.command config setting.

-V, --version

Show version and exit.

-w, --warn-only

Warn, instead of failing, when shell commands fail.

Shell tab completion

Generating a completion script

Invoke’s philosophy is to implement generic APIs and then “bake in” a few common use cases built on top of those APIs; tab completion is no different. Generic tab completion functionality (outputting a shell-compatible list of completion tokens for a given command line context) is provided by the --complete core CLI option described above.

However, you probably won’t need to use that flag yourself: we distribute a handful of ready-made wrapper scripts aimed at the most common shells like bash and zsh (plus others). These scripts can be automatically generated from Invoke or any Invoke-driven command-line tool, using --print-completion-script; the printed scripts will contain the correct binary name(s) for the program generating them.

For example, the following command prints (to stdout) a script which works for zsh, instructs zsh to use it for the inv and invoke programs, and calls invoke --complete at runtime to get dynamic completion information:

$ invoke --print-completion-script zsh

Note

You’ll probably want to source this command or store its output somewhere permanently; more on that in the next section.

Similarly, the Fabric tool inherits from Invoke, and only has a single binary name (fab); if you wanted to get Fabric completion in bash, you would say:

$ fab --print-completion-script bash

In the rest of this section, we’ll use inv in examples, but please remember to replace it with the program you’re actually using, if it’s not Invoke itself!

Sourcing the script

There are a few ways to utilize the output of the above commands, depending on your needs, where the program is installed, and your shell:

  • The simplest and least disruptive method is to source the printed completion script inline, which doesn’t place anything on disk, and will only affect the current shell session:

    $ source <(inv --print-completion-script zsh)

  • If you’ve got the program available in your system’s global Python interpreter (and you’re okay with running the program at the startup of each shell session - Python’s speed is admittedly not its strong point) you could add that snippet to your shell’s startup file, such as ~/.zshrc or ~/.bashrc.

  • If the program’s available globally but you’d prefer to avoid running an extra Python program at shell startup, you can cache the output of the command in its own file; where this file lives is entirely up to you and how your shell is configured. For example, you might just drop it into your home directory as a hidden file:

    $ inv --print-completion-script zsh > ~/.invoke-completion.sh

    and then perhaps add the following to the end of ~/.zshrc:

    source ~/.invoke-completion.sh

    But again, this is entirely up to you and your shell.

    Note

    If you’re using fish, you must use this tactic, as our fish completion script is not suitable for direct sourcing. Fish shell users should direct the output of the command to a file in the ~/.config/fish/completions/ directory.

  • Finally, if your copy of the needing-completion program is only installed in a specific environment like a virtualenv, you can use either of the above techniques:

    • Caching the output and referencing it in a global shell startup file will still work in this case, as it does not require the program to be available when the shell loads – only when you actually attempt to tab complete.
    • Using the source <(inv --print-completion-script yourshell) approach will work as long as you place it in some appropriate per-environment startup file, which will vary depending on how you manage Python environments. For example, if you use virtualenvwrapper, you could append the source line in /path/to/virtualenv/bin/postactivate.

Utilizing tab completion itself

You’ve ensured that the completion script is active in your environment - what have you gained?

  • By default, tabbing after typing inv or invoke will display task names from your current directory/project’s tasks file.

  • Tabbing after typing a dash (-) or double dash (--) will display valid options/flags for the current context: core Invoke options if no task names have been typed yet; options for the most recently typed task otherwise.

    • Tabbing while typing a partial long option will complete matching long options, using your shell’s native substring completion. E.g. if no task names have been typed yet, --e<tab> will offer --echo as a completion option.

  • Hitting tab when the most recent typed/completed token is a flag which takes a value, will ‘fall through’ to your shell’s native filename completion.

    • For example, prior to typing a task name, --config <tab> will complete local file paths to assist in filling in a config file.