# LibTmux::Async.open

- **Module:** LibTmux
- **Package:** libtmux-async
- **Language:** Ruby
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-ruby/blob/d8ce4bbee0ca7748a81929f81f7d8d07f8c51267/gems/libtmux-async/lib/libtmux/async.rb#L31
- **Page:** https://libtmux.org/en/ruby/v0.1.0.alpha.3/reference/libtmux-async-open/

```
def self.open: [T] (
  server: ::LibTmux::Server,
  ?parent: untyped,
  **untyped
) {
  (::LibTmux::Async::Scope) -> T
} -> T
```

Behavior: Async scope.

Behavior contract: Async scope.

## Examples

Open an Async scope over an existing server and capture every pane concurrently, in input order. Use Ruby 4.0.7, Bundler, Git and tmux 3.3a or newer on Unix, with /bin/cat and /bin/sh available. In an empty directory, fetch the documented library revision:

```console
$ git clone https://github.com/libtmux/libtmux-ruby.git libtmux-source && \
  git -C libtmux-source checkout d8ce4bbee0ca7748a81929f81f7d8d07f8c51267
```

Save this dependency file as Gemfile:

```ruby
source "https://rubygems.org"

gem "libtmux-async", path: "libtmux-source/gems/libtmux-async"
```

Save this complete program as async_scope.rb. Its Server.start block owns a private tmux server and stops it on exit, including after an error.

[Source example](https://github.com/libtmux/libtmux-ruby/blob/d8ce4bbee0ca7748a81929f81f7d8d07f8c51267/examples/api/async_scope.rb).

```ruby
# frozen_string_literal: true

begin
  # docs:begin main
  require "libtmux"
  require "libtmux/async"

  LibTmux::Server.start do |server|
    server.new_session(name: "work", command: ["/bin/cat"])
    server.new_session(name: "logs", command: ["/bin/cat"])
    Async do |parent|
      LibTmux::Async.open(parent: parent, server: server) do |scope|
        refs = scope.server.list_panes.map(&:ref)
        screens = scope.map(refs, concurrency: 2) { |ref| scope.server.pane(ref).capture }
        puts "captured panes: #{screens.length}"
        puts "all succeeded: #{screens.all?(&:success?)}"
      end
    end.wait
  end
  # docs:end main
rescue StandardError => error
  warn "#{error.class}: #{error.message}"
  exit 1
end
```

Install the runtime dependencies and run the saved program. An operation or cleanup error makes it exit unsuccessfully:

```console
$ bundle config set --local path vendor/bundle && \
  bundle install --jobs 2 && \
  bundle exec ruby async_scope.rb
```

Expected output:

```text
captured panes: 2
all succeeded: true
```

## Type parameters

- `T`

## Parameters

- `server` (`::LibTmux::Server`)
- `parent` (`untyped`)
- `kwargs` (`untyped`)

## Raises

- `ArgumentError`