# Attach and send keys

Source: https://libtmux.org/en/py/latest/examples/attach-and-send-keys/

> Get a session handle, send a command to a pane, and capture output.

Get a session handle, send a command to a pane, and capture output. These
examples use libtmux from your program; to attach your terminal interactively,
see [Attaching to tmux](https://libtmux.org/en/py/latest/guides/attaching-to-tmux/).

The examples include setup, error handling, and cleanup. [Source and
verification](https://libtmux.org/en/py/latest/examples/attach-and-send-keys/#where-this-comes-from) identifies their files and checks.

```python
>>> import libtmux
>>> server = libtmux.Server()
>>> session = server.new_session(session_name='demo')
Session(...)

>>> window = session.active_window
>>> pane = window.split(shell='sh')
>>> pane.capture_pane()
['$']

>>> pane.send_keys('echo "Hello world"', enter=True)

>>> pane.capture_pane()
['$ echo "Hello world"', 'Hello world', '$']
```

## Finding an existing session instead

For a script that runs repeatedly, look up a session before creating it.
[Attaching to
tmux](https://libtmux.org/en/py/latest/guides/attaching-to-tmux/#finding-a-session-instead-of-always-creating-one)
shows that pattern, and [Filtering and querying, in
practice](https://libtmux.org/en/py/latest/guides/querying-and-filtering/) covers absent and ambiguous matches.

## Where this comes from

**Source:** [`src/libtmux/server.py`](<https://github.com/tmux-python/libtmux/blob/8e0ce38400618bd783e6276270dd7f5d8cb283ea/src/libtmux/server.py>), [`session.py`](<https://github.com/tmux-python/libtmux/blob/8e0ce38400618bd783e6276270dd7f5d8cb283ea/src/libtmux/session.py>), [`pane.py`](<https://github.com/tmux-python/libtmux/blob/8e0ce38400618bd783e6276270dd7f5d8cb283ea/src/libtmux/pane.py>) docstrings

**In this page:** hand-quoted, composed from three separate docstrings

**Checked by:** `pytest` runs every `>>>` doctest (`testpaths` includes
`src/libtmux`) against a real, isolated tmux session on every test run

### Source inclusion

A `file="..."` fence reads the named source during the site build. Hand-quoted
excerpts are copies; their source files and regions are listed above.