Environment

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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 and show-environment for new processes to inherit. Like the tables in Options and hooks, this persistent store has explicit scopes.

Locating yourself from inside a paneLink to section

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. Ports expose different levels of environment lookup:

PythonLink to section

Server: Server.from_env()

Session: Session.from_env()

Window: Window.from_env()

Pane: Pane.from_env()

TypeScriptLink to section

Server: Not listed.

Session: Session.fromEnv()

Window: Not listed.

Pane: Not listed.

GoLink to section

Server: NewServerFromEnv(env)

Session: SessionFromEnv(ctx, env)

Window: WindowFromEnv(ctx, env)

Pane: PaneFromEnv(ctx, env)

RustLink to section

Server: Server::from_env()

Session: Session::from_env(&server)

Window: Window::from_env(&server)

Pane: Pane::from_env(&server)

JavaLink to section

Server: Not listed.

Session: Not listed.

Window: Not listed.

Pane: See the Java context example below.

.NETLink to section

Server: Server.FromEnvironment(env)

Session: Session.FromEnvironmentAsync()

Window: Window.FromEnvironmentAsync()

Pane: Pane.FromEnvironmentAsync()

C++Link to section

Server: Server::from_env()

Session: Not listed.

Window: Not listed.

Pane: Not listed.

SwiftLink to section

Server: TmuxContext.current()

Session: TmuxContext.current() (same call: see below)

Window: Not listed.

Pane: Not listed.

ExamplesLink to section

Python, Go, and .NET provide standalone environment lookups at each level. Rust’s Session, Window, and Pane::from_env require an existing &Server. TypeScript provides Session.fromEnv(); this page lists no equivalent for its other object types.

A process not started inside a pane has nothing truthful to answer with, so every one of these raises rather than guessing: Python’s NotInsideTmux, Go’s FromEnvError, .NET’s TmuxObjectNotFoundException, and so on, each naming the missing or malformed variable rather than returning an empty or default object.

Java and C++ stop short of the paneLink to section

Neither port gives you a live object back the way the other five do, and they stop at different points:

• C++ provides Server::from_env() to select the socket. Use the resulting server to resolve sessions or panes.

• Java parses TMUX and TMUX_PANE into identifiers: socket path, server PID, SessionId, and Optional<PaneId>. It returns context data rather than a live pane handle:

Swift context fieldsLink to section

Swift’s TmuxContext.current() parses the socket path, server PID, and session ID from TMUX. It does not read TMUX_PANE, so it cannot identify the current pane:

Read TMUX_PANE separately if you need the pane ID; TmuxContext does not provide it.

tmux’s own environment variable storeLink to section

Like Options and hooks, tmux’s persistent environment store has global and per-session scopes. It is read with show-environment and updated with set-environment. Newly spawned processes inherit it; existing processes retain their own environments.

PythonLink to section

Set: server.set_environment(name, value), session.set_environment(...)

Read all: server.show_environment(), session.show_environment()

Unset: server.unset_environment(name). See below for .remove_environment().

TypeScriptLink to section

Set: server.setEnvironment(name, value), session.setEnvironment(...)

Read all: server.showEnvironment(), session.showEnvironment()

Unset: server.unsetEnvironment(name), session.unsetEnvironment(name)

GoLink to section

Set: server.SetEnvironment(ctx, name, value, opts) (global, -g)

Read all: server.ShowEnvironment(ctx)

Unset: server.UnsetEnvironment(ctx, name)

RustLink to section

Set: server.set_environment(...), session.set_environment(...)

Read all: server.environment_all(), session.environment_all()

Unset: server.unset_environment(name), session.unset_environment(name)

JavaLink to section

Set: Not documented here; see the Java and C++ note below.

Read all: Not documented here; see the Java and C++ note below.

Unset: Not documented here; see the Java and C++ note below.

.NETLink to section

Set: server.Environment.SetAsync(name, value), session.Environment.SetAsync(...)

Read all: server.Environment.GetAllAsync()

Unset: server.Environment.UnsetAsync(name), .RemoveAsync(name)

C++Link to section

Set: Not documented here; see the Java and C++ note below.

Read all: Not documented here; see the Java and C++ note below.

Unset: Not documented here; see the Java and C++ note below.

SwiftLink to section

Set: server.setEnvironment(name, to: value, in: scope)

Read all: server.environment(scope)

Unset: server.unsetEnvironment(name, in: scope), .removeEnvironment(name, in:)

ExamplesLink to section

Python’s set_environment writes a value, and unset_environment (-u) removes the entry. remove_environment (-r) marks the variable for exclusion from new processes, including when tmux inherited it at server startup; the listing retains it as -NAME. Swift exposes the same distinction through setEnvironment, unsetEnvironment, and removeEnvironment. A remove operation is not documented here for TypeScript, Go, or Rust.

Java and C++: no verified access to this table at allLink to section

Java and C++ examples here cover environment values supplied at process creation, not reads or writes to an existing persistent table. Java’s SessionSpec.Builder.environment(Map), WindowSpec.Builder.environment(Map), and SplitSpec.Builder.environment(Map) pass initial variables to new-session -e, new-window -e, and split-window -e. Consult the port reference if you need to change the environment of an existing session.