# LibTmux::Selection#where

- **Module:** LibTmux
- **Package:** libtmux
- **Language:** Ruby
- **Kind:** method
- **Source:** https://github.com/libtmux/libtmux-ruby/blob/da7b6191b9439e3c84fa1c9eeaa9168263ee7af4/gems/libtmux/lib/libtmux/selection.rb#L53
- **Page:** https://libtmux.org/en/ruby/v0.1.1/reference/libtmux-selection-where/

```
def where: (
  ?untyped,
  **untyped
) -> ::LibTmux::Selection[Elem]
```

Behavior: Selections.

Behavior contract: Selections.

## Examples

Filter a captured snapshot, distinguish a missing session, and acquire a fresh pane selection. one raises unless exactly one record matches; one_or_nil returns nil only for zero matches. 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 `query.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/query.rb).

```ruby
# frozen_string_literal: true

begin
  # docs:begin main
  require "libtmux"

  LibTmux::Server.start do |server|
    work = server.new_session(name: "work", command: ["/bin/cat"], receipt: true)
    server.new_session(name: "logs", command: ["/bin/cat"])
    snapshot = server.snapshot
    session = snapshot.sessions.where(name: "work").one
    puts "matching session: #{session.name}"
    missing = snapshot.sessions.one_or_nil(name: "missing")
    puts "missing session: #{missing.nil?}"
    panes = server.search_panes(where: {id: work.pane.id})
    puts "matching pane: #{panes.one.id}"
  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 query.rb
```

Expected output:

```text
matching session: work
missing session: true
matching pane: %0
```

## Parameters

- `arg1` (`untyped`)
- `kwargs` (`untyped`)

## Raises

- `ArgumentError`