# LibTmux::Server#open_control

- **Module:** LibTmux
- **Package:** libtmux
- **Language:** Ruby
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-ruby/blob/da7b6191b9439e3c84fa1c9eeaa9168263ee7af4/gems/libtmux/lib/libtmux/server.rb#L290
- **Page:** https://libtmux.org/en/ruby/v0.1.1/reference/libtmux-server-open_control/

```
def open_control: [T] (
  session: ::LibTmux::EntityRef,
  ?reconnect: ::LibTmux::ControlConnection?,
  **untyped
) {
  (::LibTmux::ControlConnection) -> T
} -> T

def open_control: (
  session: ::LibTmux::EntityRef,
  ?reconnect: ::LibTmux::ControlConnection?,
  **untyped
) -> ::LibTmux::ControlConnection
```

Behavior: Control connections.

Behavior contract: Control connections.

## Examples

Open a control connection, run one command through it, and read the notification tmux sends when a window is renamed. Use Ruby 3.3 or newer with Bundler, and tmux 3.3a or newer, on Unix with `/bin/cat` and `/bin/sh` available. In an empty directory, save this `Gemfile`:

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

gem "libtmux", "0.1.1"
```

Save this complete program as `control.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/da7b6191b9439e3c84fa1c9eeaa9168263ee7af4/examples/api/control.rb).

```ruby
# frozen_string_literal: true

begin
  # docs:begin main
  require "libtmux"

  LibTmux::Server.start do |server|
    session = server.new_session(name: "work", command: ["/bin/cat"])
    window = session.list_windows.fetch(0)
    server.open_control(session: session.ref) do |control|
      reply = control.exchange("display-message -p ready", timeout: 5)
      puts "reply: #{reply.blocks.last.body.strip}"
      events = control.subscribe(max_events: 64, max_bytes: 65_536)
      window.rename("renamed")
      event = events.next(timeout: 5) until event&.raw&.start_with?("%window-renamed")
      puts "event: #{event.raw.strip}"
    end
  end
  # docs:end main
rescue StandardError => error
  warn "#{error.class}: #{error.message}"
  exit 1
end
```

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

```console
$ bundle install && \
  bundle exec ruby control.rb
```

Expected output:

```text
reply: ready
event: %window-renamed @0 renamed
```

## Type parameters

- `T` (for `open_control(session, reconnect, kwargs) [overload 1]`)

## Parameters

- `session` (`::LibTmux::EntityRef`)
- `reconnect` (`::LibTmux::ControlConnection?`)
- `kwargs` (`untyped`)