Commands and control mode

Choose command calls for bounded operations and a control connection when you need a persistent tmux client. Closing a client releases its resources; it does not mean the tmux server should be stopped.

The direct Server API blocks until the operation completes. Using.resource closes its client resources. For effectful applications, the execution guide covers the Cats Effect and Ox packages.

Setup and run¶

Use an empty directory on Linux with Git, tmux 3.2a or newer, and JDK 25. Save the project files and launcher below, then save any complete program on this page. Each program has its own imports and entry point.

The pinned source checkout supplies the Gradle wrapper and the library dependency.

rootProject.name = "connect"
includeBuild("libtmux-source") {
    dependencySubstitution {
        substitute(module("io.github.libtmux:libtmux-scala_3"))
            .using(project(":libtmux-scala"))
    }
}

val example = providers.gradleProperty("example").getOrElse("Local")

plugins {
    application
    scala
}

repositories { mavenCentral() }
dependencies {
    implementation("org.scala-lang:scala3-library_3:3.9.0")
    implementation("io.github.libtmux:libtmux-scala_3:0.0.1-alpha.17-SNAPSHOT")
}
java { toolchain { languageVersion.set(JavaLanguageVersion.of(25)) } }
sourceSets.main { scala.srcDir("."); scala.include("${example}.scala") }
application { mainClass.set(example) }

org.gradle.jvmargs=-Xmx2g -XX:MaxMetaspaceSize=768m -Dfile.encoding=UTF-8
kotlin.daemon.jvmargs=-Xmx2g
org.gradle.workers.max=2

The launcher creates two sessions on a private socket: work-one with an editor window, and work-two with a logs window. Each pane runs cat so it stays alive. It stops only this server when the program finishes or fails. If shutdown fails, it reports the retained directory and exits with an error.

#!/bin/sh
set -eu

binary=$(command -v tmux)
mkdir -p /tmp/libtmux-java-dev
directory=$(mktemp -d /tmp/libtmux-java-dev/query.XXXXXX)
socket="$directory/tmux.sock"

cleanup() {
    status=$?
    trap - 0 HUP INT TERM
    if [ -S "$socket" ] && ! "$binary" -S "$socket" kill-server; then
        printf 'Cannot stop tmux; kept %s\n' "$directory" >&2
        exit 1
    fi
    rm -rf "$directory" || exit 1
    exit "$status"
}
trap cleanup 0
trap 'exit 1' HUP INT TERM

unset TMUX TMUX_PANE
export LIBTMUX_SOCKET_PATH="$socket" TMUX_BIN="$binary"
"$binary" -S "$socket" -f /dev/null new-session -d -s work-one -n editor /bin/cat
"$binary" -S "$socket" new-session -d -s work-two -n logs /bin/cat
"$@"
"$binary" -S "$socket" has-session -t '=work-one'

Fetch the library revision used by these examples:

$ git clone https://github.com/libtmux/libtmux-java libtmux-source &&
  git -C libtmux-source checkout be1d62fbaa1aa634c687e1c50bceeb09ef0b8a15

Each run starts from the same two-session fixture. Programs do not depend on another example having run first. Their assertions fail if the observed result differs.

Run a bounded command and inspect its result¶

Read the session list and filter it locally. The connection uses a five-second timeout so an unavailable server fails visibly.

import io.github.libtmux.{ServerConfig, ServerEndpoint}
import io.github.libtmux.scaladsl.*
import io.github.libtmux.scaladsl.query.*
import java.nio.file.Path
import java.time.Duration
import scala.util.Using
import scala.jdk.CollectionConverters.*

object Local {
  def main(args: Array[String]): Unit = {
    val socket = sys.env.getOrElse("LIBTMUX_SOCKET_PATH",
      throw new IllegalArgumentException("Set LIBTMUX_SOCKET_PATH to an existing socket"))
    val config = ServerConfig.builder()
      .endpoint(ServerEndpoint.socketPath(Path.of(socket)))
      .defaultTimeout(Duration.ofSeconds(5))
      .build()
    Using.resource(Server.open(config)) { server =>
      val sessions = server.sessions()
      val matching = sessions.matching(Session.name.startsWith("work-"))
      val names = matching.map(_.name).sorted
      assert(names == Vector("work-one", "work-two"))
      println(names.mkString(", "))
      // Filtering the captured vector makes no new tmux calls.
      assert(sessions.filter(_.name.startsWith("work-")) == matching)
      val onlyOne = Session.name.startsWith("work-") && Session.name.endsWith("one")
      assert(sessions.matching(onlyOne).head.name == "work-one")
      val either = Session.name.is("work-one") || Session.name.is("work-two")
      assert(sessions.matching(either).size == 2)
      assert(sessions.matching(!Session.name.is("work-one")).head.name == "work-two")
    }
  }
}

$ sh run.sh ./libtmux-source/gradlew --project-dir . run \
  -Pexample=Local --console=plain --max-workers=2

Expected program output:

work-one, work-two

Open and close a control client¶

Send list-sessions over a persistent control connection, verify the response, then close the control client. A subsequent ordinary read verifies the tmux server still has both sessions.

import io.github.libtmux.{ServerConfig, ServerEndpoint}
import io.github.libtmux.scaladsl.*
import io.github.libtmux.scaladsl.query.*
import java.nio.file.Path
import java.time.Duration
import scala.util.Using
import scala.jdk.CollectionConverters.*

object Control {
  def main(args: Array[String]): Unit = {
    val socket = sys.env.getOrElse("LIBTMUX_SOCKET_PATH",
      throw new IllegalArgumentException("Set LIBTMUX_SOCKET_PATH to an existing socket"))
    val config = ServerConfig.builder()
      .endpoint(ServerEndpoint.socketPath(Path.of(socket)))
      .defaultTimeout(Duration.ofSeconds(5))
      .build()
    Using.resource(Server.open(config)) { server =>
      val session = server.sessions().find(_.name == "work-one").get
      Using.resource(server.control(session)) { control =>
        val reply = control.send("list-sessions", "-F", "#{session_name}")
        require(reply.succeeded(), s"tmux rejected list-sessions: ${reply.outcome()}")
        val names = reply.lines().asScala.toVector.sorted
        assert(names == Vector("work-one", "work-two"))
        println(names.mkString(", "))
      }
      assert(server.sessions().size == 2)
      println("control client closed; server still running")
    }
  }
}

$ sh run.sh ./libtmux-source/gradlew --project-dir . run \
  -Pexample=Control --console=plain --max-workers=2

Expected program output:

work-one, work-two
control client closed; server still running

Timeouts and ownership¶

An operation that times out may already have reached tmux. Read the current state before retrying a mutation such as creating a window. A cancellation signal does not roll back a completed tmux command.

Here the launcher owns the private server and stops it after the program exits. An application connecting to an existing server should close its own client resources and leave that server running. See attaching to tmux for the connection-only example.

Scripting & web

Compiled & native

JVM

.NET

tmux

Commands and control mode

Setup and run¶

Run a bounded command and inspect its result¶

Open and close a control client¶

Timeouts and ownership¶