# Environment

Source: https://libtmux.org/en/rs/latest/topics/environment/

> Locate tmux objects from process variables and manage the environment inherited by new panes.

tmux exposes two environment APIs. Process variables such as `TMUX` and
`TMUX_PANE` let code inside a pane identify its server and pane. The server also
stores variables through [`set-environment`](https://libtmux.org/en/tmux/latest/manual/set-environment/) and [`show-environment`](https://libtmux.org/en/tmux/latest/manual/show-environment/) for new
processes to inherit. Like the tables in [Options and
hooks](https://libtmux.org/en/rs/latest/topics/options-and-hooks/), this persistent store has explicit scopes.

## Locating yourself from inside a pane

Inside a pane, `TMUX` contains `<socket path>,<server pid>,<session id>`, and
`TMUX_PANE` contains the pane ID, such as `%1`. Use these variables to locate
the current tmux objects. Select the object your operation needs:

**Server:** [`Server::from_env()`](<https://libtmux.org/en/rs/latest/reference/server-server-from_env/>)

**Session:** [`Session::from_env(&server)`](<https://libtmux.org/en/rs/latest/reference/session-session-from_env/>)

**Window:** [`Window::from_env(&server)`](<https://libtmux.org/en/rs/latest/reference/window-window-from_env/>)

**Pane:** [`Pane::from_env(&server)`](<https://libtmux.org/en/rs/latest/reference/pane-pane-from_env/>)

### Examples

[`Session`](<https://libtmux.org/en/rs/latest/reference/session-session/>), [`Window`](<https://libtmux.org/en/rs/latest/reference/window-window/>), and [`Pane::from_env`](<https://libtmux.org/en/rs/latest/reference/pane-pane-from_env/>) require an existing `&Server`.

```rust
let server = libtmux::Server::from_env()?;
let session = libtmux::Session::from_env(&server).await?; // Option<Session>
let window = libtmux::Window::from_env(&server).await?;
let pane = libtmux::Pane::from_env(&server).await?;
```

Environment lookup requires valid tmux targeting variables. If your process
can run outside tmux, handle that case before using the result.

## tmux's own environment variable store

Like [Options and hooks](https://libtmux.org/en/rs/latest/topics/options-and-hooks/),
tmux's persistent environment store has global and per-session scopes. It is
read with [`show-environment`](https://libtmux.org/en/tmux/latest/manual/show-environment/) and updated with [`set-environment`](https://libtmux.org/en/tmux/latest/manual/set-environment/). Newly spawned
processes inherit it; existing processes retain their own environments.

**Set:** [`server.set_environment(...)`](<https://libtmux.org/en/rs/latest/reference/server-server-set_environment/>), [`session.set_environment(...)`](<https://libtmux.org/en/rs/latest/reference/session-session-set_environment/>)

**Read all:** [`server.environment_all()`](<https://libtmux.org/en/rs/latest/reference/server-server-environment_all/>), [`session.environment_all()`](<https://libtmux.org/en/rs/latest/reference/session-session-environment_all/>)

**Unset:** [`server.unset_environment(name)`](<https://libtmux.org/en/rs/latest/reference/server-server-unset_environment/>), [`session.unset_environment(name)`](<https://libtmux.org/en/rs/latest/reference/session-session-unset_environment/>)

### Examples

```rust
server.set_environment("EDITOR", "vim").await?;
session.set_environment("EDITOR", "hx").await?;
session.environment_all().await?;
```

[`set-environment`](https://libtmux.org/en/tmux/latest/manual/set-environment/) writes a value. Its `-u` flag removes the entry, while `-r`
marks the variable for exclusion from new processes, including values tmux
inherited at startup. The listing retains an excluded variable as `-NAME`.