# Environment

Source: https://libtmux.org/en/ts/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/ts/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:** Not listed.

**Session:** [`Session.fromEnv()`](<https://libtmux.org/en/ts/latest/reference/session-session-fromenv/>)

**Window:** Not listed.

**Pane:** Not listed.

### Examples

Use [`Session.fromEnv()`](<https://libtmux.org/en/ts/latest/reference/session-session-fromenv/>) to resolve the session of the current process.

```typescript
const session = await Session.fromEnv();
```

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/ts/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.setEnvironment(name, value)`](<https://libtmux.org/en/ts/latest/reference/server-server-setenvironment/>), [`session.setEnvironment(...)`](<https://libtmux.org/en/ts/latest/reference/session-session-setenvironment/>)

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

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

### Examples

```typescript
await server.setEnvironment("EDITOR", "vim");
await session.setEnvironment("EDITOR", "hx");
await session.showEnvironment();
```

[`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`.