# Environment

Source: https://libtmux.org/en/swift/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/swift/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:** [`TmuxContext.current()`](<https://libtmux.org/en/swift/latest/reference/tmuxcontext-current(environment-)/>)

**Session:** [`TmuxContext.current()`](<https://libtmux.org/en/swift/latest/reference/tmuxcontext-current(environment-)/>) (same call: see below)

**Window:** Not listed.

**Pane:** Not listed.

### Examples

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

<a id="swift-reads-less-than-it-could"></a>

### Swift context fields

Swift's [`TmuxContext.current()`](<https://libtmux.org/en/swift/latest/reference/tmuxcontext-current(environment-)/>) parses the socket path, server PID, and session
ID from `TMUX`. It does not read `TMUX_PANE`, so it cannot identify the current
pane:

```swift
let context = TmuxContext.current()! // socket path, server pid, session id
let server = try context.server()
```

Read `TMUX_PANE` separately if you need the pane ID; [`TmuxContext`](<https://libtmux.org/en/swift/latest/reference/tmuxcontext/>) does not
provide it.

## tmux's own environment variable store

Like [Options and hooks](https://libtmux.org/en/swift/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, to: value, in: scope)`](<https://libtmux.org/en/swift/latest/reference/server-setenvironment(_-to-in-)/>)

**Read all:** [`server.environment(scope)`](<https://libtmux.org/en/swift/latest/reference/server-environment(_-)/>)

**Unset:** [`server.unsetEnvironment(name, in: scope)`](<https://libtmux.org/en/swift/latest/reference/server-unsetenvironment(_-in-)/>), [`.removeEnvironment(name,
in:)`](<https://libtmux.org/en/swift/latest/reference/server-removeenvironment(_-in-)/>)

### Examples

```swift
try await server.setEnvironment("EDITOR", to: "vim", in: .global)
try await server.setEnvironment("EDITOR", to: "hx", in: .session(session.id.rawValue))
try await server.environment(.session(session.id.rawValue))
```

[`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`.

Use [`unsetEnvironment`](<https://libtmux.org/en/swift/latest/reference/server-unsetenvironment(_-in-)/>) for `-u`, or [`removeEnvironment`](<https://libtmux.org/en/swift/latest/reference/server-removeenvironment(_-in-)/>) for `-r`.