# LibTmux::ControlConnection#subscribe

- **Module:** LibTmux
- **Package:** libtmux
- **Language:** Ruby
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-ruby/blob/d8ce4bbee0ca7748a81929f81f7d8d07f8c51267/gems/libtmux/lib/libtmux/control.rb#L507
- **Page:** https://libtmux.org/en/ruby/v0.1.0.alpha.3/reference/libtmux-controlconnection-subscribe/

```
def subscribe: (
  ?pane_id: ::String?,
  ?mode: :reliable | :tail,
  ?max_bytes: ::Integer,
  ?max_events: ::Integer
) -> ::LibTmux::ControlSubscription
```

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

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/d8ce4bbee0ca7748a81929f81f7d8d07f8c51267/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 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 control.rb
```

Expected output:

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

## Parameters

- `pane_id` (`::String?`)
- `mode` (`:reliable | :tail`)
- `max_bytes` (`::Integer`)
- `max_events` (`::Integer`)