feat(cwd-pane): Keeping the cwd when opening new panes (#691)

* feat(cwd-pane): Add a new trait to get the cwd of a given pid

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Allow for setting the cwd when spawning a new terminal

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Add an active_pane field to the Pty struct

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Update Pty with Tab's active pane id

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Refactor spawn_terminal to use cwd by default

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Fix tests and lints

Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

* feat(cwd-pane): Fix formatting

* feat(cwd-pane): Refactor child pid fetching to handle errors better

Instead of panicking when transfering the process id of the forked child
command we just return an empty process id.

* feat(cwd-pane): Add non Linux/MacOS targets for the get_cwd method.

This will allow Zellij to compile on non Linux/MacOS targets without
having an inherited cwd.

* feat(cwd-pane): Refactor spawn_terminal method to use ChildId struct.

The spawn_terminal methods been refactored to use the ChildId struct in
order to clarify what the Pid's returned by it are. The documentation
for the ChildId struct was improved as well.

* feat(cwd-pane): Fix tests/lints

Co-authored-by: Jesse Tuchsen <not@disclosing>
Co-authored-by: Quentin Rasmont <qrasmont@gmail.com>

9 files changed, 295 insertions, 143 deletions

diff --git a/Cargo.lock b/Cargo.lock
index 6c2cdcd3..7bd709ac 100644
--- a/Cargo.lock
+++ b/Cargo.lock
@@ -4,11 +4,11 @@ version = 3
 
 [[package]]
 name = "addr2line"
-version = "0.16.0"
+version = "0.15.2"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "3e61f2b7f93d2c7d2b08263acaa4a363b3e276806c68af6134c44f523bf1aacd"
+checksum = "e7a2e47a1fbe209ee101dd6d61285226744c6c8d3c21c8dc878ba6cb9f467f3a"
 dependencies = [
- "gimli 0.25.0",
+ "gimli 0.24.0",
 ]
 
 [[package]]
@@ -19,9 +19,9 @@ checksum = "f26201604c87b1e01bd3d98f8d5d9a8fcbb815e8cedb41ffccbeb4bf593a35fe"
 
 [[package]]
 name = "aho-corasick"
-version = "0.7.18"
+version = "0.7.15"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "1e37cfd5e7657ada45f742d6e99ca5788580b5c529dc78faf11ece6dc702656f"
+checksum = "7404febffaa47dac81aa44dba71523c9d069b1bdc50a77db41195149e17f68e5"
 dependencies = [
  "memchr",
 ]
@@ -227,16 +227,16 @@ checksum = "cdb031dd78e28731d87d56cc8ffef4a8f36ca26c38fe2de700543e627f8a464a"
 
 [[package]]
 name = "backtrace"
-version = "0.3.61"
+version = "0.3.59"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "e7a905d892734eea339e896738c14b9afce22b5318f64b951e70bf3844419b01"
+checksum = "4717cfcbfaa661a0fd48f8453951837ae7e8f81e481fbb136e3202d72805a744"
 dependencies = [
  "addr2line",
  "cc",
  "cfg-if 1.0.0",
  "libc",
  "miniz_oxide",
- "object 0.26.0",
+ "object 0.24.0",
  "rustc-demangle",
 ]
 
@@ -622,6 +622,26 @@ dependencies = [
 ]
 
 [[package]]
+name = "darwin-libproc"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "cc629b7cf42586fee31dae31f9ab73fa5ff5f0170016aa61be5fcbc12a90c516"
+dependencies = [
+ "darwin-libproc-sys",
+ "libc",
+ "memchr",
+]
+
+[[package]]
+name = "darwin-libproc-sys"
+version = "0.2.0"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+checksum = "ef0aa083b94c54aa4cfd9bbfd37856714c139d1dc511af80270558c7ba3b4816"
+dependencies = [
+ "libc",
+]
+
+[[package]]
 name = "derivative"
 version = "2.2.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
@@ -897,9 +917,9 @@ dependencies = [
 
 [[package]]
 name = "gimli"
-version = "0.25.0"
+version = "0.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "f0a01e0497841a3b2db4f8afa483cce65f7e96a3498bd6c541734792aeac8fe7"
+checksum = "0e4075386626662786ddb0ec9081e7c7eeb1ba31951f447ca780ef9f5d568189"
 
 [[package]]
 name = "gloo-timers"
@@ -1188,9 +1208,9 @@ dependencies = [
 
 [[package]]
 name = "memchr"
-version = "2.4.0"
+version = "2.3.4"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "b16bd47d9e329435e309c58469fe0791c2d0d1ba96ec0954152a5ae2b04387dc"
+checksum = "0ee1c47aaa256ecabcaea351eae4a9b01ef39ed810004e298d2511ed284b1525"
 
 [[package]]
 name = "memmap2"
@@ -1325,12 +1345,9 @@ dependencies = [
 
 [[package]]
 name = "object"
-version = "0.26.0"
+version = "0.24.0"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "c55827317fb4c08822499848a14237d2874d6f139828893017237e7ab93eb386"
-dependencies = [
- "memchr",
-]
+checksum = "1a5b3dd1c072ee7963717671d1ca129f1048fda25edea6b752bfc71ac8854170"
 
 [[package]]
 name = "once_cell"
@@ -1675,9 +1692,9 @@ dependencies = [
 
 [[package]]
 name = "regex"
-version = "1.5.4"
+version = "1.4.6"
 source = "registry+https://github.com/rust-lang/crates.io-index"
-checksum = "d07a8629359eb56f1e2fb1652bb04212c072a87ba68546a04065d525673ac461"
+checksum = "2a26af418b574bd56588335b3a3659a65725d4e636eb1016c2f9e3b38c7cc759"
 dependencies = [
  "aho-corasick",
  "memchr",
@@ -2652,9 +2669,11 @@ dependencies = [
  "ansi_term 0.12.1",
  "async-trait",
  "base64",
+ "byteorder",
  "cassowary",
  "chrono",
  "daemonize",
+ "darwin-libproc",
  "insta",
  "log",
  "serde_json",
diff --git a/zellij-server/Cargo.toml b/zellij-server/Cargo.toml
index fe56b742..1c8c986b 100644
--- a/zellij-server/Cargo.toml
+++ b/zellij-server/Cargo.toml
@@ -12,6 +12,7 @@ license = "MIT"
 ansi_term = "0.12.1"
 async-trait = "0.1.50"
 base64 = "0.13.0"
+byteorder = "1.4.3"
 daemonize = "0.4.1"
 serde_json = "1.0"
 unicode-width = "0.1.8"
@@ -23,6 +24,9 @@ log = "0.4.14"
 typetag = "0.1.7"
 chrono = "0.4.19"
 
+[target.'cfg(target_os = "macos")'.dependencies]
+darwin-libproc = "0.2.0"
+
 [dev-dependencies]
 insta = "1.6.0"
 
diff --git a/zellij-server/src/os_input_output.rs b/zellij-server/src/os_input_output.rs
index 05980805..e24b24b4 100644
--- a/zellij-server/src/os_input_output.rs
+++ b/zellij-server/src/os_input_output.rs
@@ -1,4 +1,8 @@
+#[cfg(target_os = "macos")]
+use darwin_libproc;
+
 use std::env;
+use std::fs;
 use std::os::unix::io::RawFd;
 use std::os::unix::process::CommandExt;
 use std::path::PathBuf;
@@ -10,7 +14,7 @@ use zellij_utils::{async_std, interprocess, libc, nix, signal_hook, zellij_tile}
 use async_std::fs::File as AsyncFile;
 use async_std::os::unix::io::FromRawFd;
 use interprocess::local_socket::LocalSocketStream;
-use nix::pty::{forkpty, Winsize};
+use nix::pty::{forkpty, ForkptyResult, Winsize};
 use nix::sys::signal::{kill, Signal};
 use nix::sys::termios;
 use nix::sys::wait::waitpid;
@@ -29,6 +33,7 @@ use zellij_utils::{
 
 use async_std::io::ReadExt;
 pub use async_trait::async_trait;
+use byteorder::{BigEndian, ByteOrder};
 
 pub use nix::unistd::Pid;
 
@@ -92,44 +97,94 @@ fn handle_command_exit(mut child: Child) {
     }
 }
 
+fn handle_fork_pty(
+    fork_pty_res: ForkptyResult,
+    cmd: RunCommand,
+    parent_fd: RawFd,
+    child_fd: RawFd,
+) -> (RawFd, ChildId) {
+    let pid_primary = fork_pty_res.master;
+    let (pid_secondary, pid_shell) = match fork_pty_res.fork_result {
+        ForkResult::Parent { child } => {
+            let pid_shell = read_from_pipe(parent_fd, child_fd);
+            (child, pid_shell)
+        }
+        ForkResult::Child => {
+            let child = unsafe {
+                let command = &mut Command::new(cmd.command);
+                if let Some(current_dir) = cmd.cwd {
+                    command.current_dir(current_dir);
+                }
+                command
+                    .args(&cmd.args)
+                    .pre_exec(|| -> std::io::Result<()> {
+                        // this is the "unsafe" part, for more details please see:
+                        // https://doc.rust-lang.org/std/os/unix/process/trait.CommandExt.html#notes-and-safety
+                        unistd::setpgid(Pid::from_raw(0), Pid::from_raw(0))
+                            .expect("failed to create a new process group");
+                        Ok(())
+                    })
+                    .spawn()
+                    .expect("failed to spawn")
+            };
+            unistd::tcsetpgrp(0, Pid::from_raw(child.id() as i32))
+                .expect("faled to set child's forceground process group");
+            write_to_pipe(child.id(), parent_fd, child_fd);
+            handle_command_exit(child);
+            ::std::process::exit(0);
+        }
+    };
+
+    (
+        pid_primary,
+        ChildId {
+            primary: pid_secondary,
+            shell: pid_shell.map(|pid| Pid::from_raw(pid as i32)),
+        },
+    )
+}
+
 /// Spawns a new terminal from the parent terminal with [`termios`](termios::Termios)
 /// `orig_termios`.
 ///
-fn handle_terminal(cmd: RunCommand, orig_termios: termios::Termios) -> (RawFd, Pid) {
-    let (pid_primary, pid_secondary): (RawFd, Pid) = {
-        match forkpty(None, Some(&orig_termios)) {
-            Ok(fork_pty_res) => {
-                let pid_primary = fork_pty_res.master;
-                let pid_secondary = match fork_pty_res.fork_result {
-                    ForkResult::Parent { child } => child,
-                    ForkResult::Child => {
-                        let child = unsafe {
-                            Command::new(cmd.command)
-                                .args(&cmd.args)
-                                .pre_exec(|| -> std::io::Result<()> {
-                                    // this is the "unsafe" part, for more details please see:
-                                    // https://doc.rust-lang.org/std/os/unix/process/trait.CommandExt.html#notes-and-safety
-                                    unistd::setpgid(Pid::from_raw(0), Pid::from_raw(0))
-                                        .expect("failed to create a new process group");
-                                    Ok(())
-                                })
-                                .spawn()
-                                .expect("failed to spawn")
-                        };
-                        unistd::tcsetpgrp(0, Pid::from_raw(child.id() as i32))
-                            .expect("faled to set child's forceground process group");
-                        handle_command_exit(child);
-                        ::std::process::exit(0);
-                    }
-                };
-                (pid_primary, pid_secondary)
-            }
-            Err(e) => {
-                panic!("failed to fork {:?}", e);
-            }
+fn handle_terminal(cmd: RunCommand, orig_termios: termios::Termios) -> (RawFd, ChildId) {
+    // Create a pipe to allow the child the communicate the shell's pid to it's
+    // parent.
+    let (parent_fd, child_fd) = unistd::pipe().expect("failed to create pipe");
+    match forkpty(None, Some(&orig_termios)) {
+        Ok(fork_pty_res) => handle_fork_pty(fork_pty_res, cmd, parent_fd, child_fd),
+        Err(e) => {
+            panic!("failed to fork {:?}", e);
         }
-    };
-    (pid_primary, pid_secondary)
+    }
+}
+
+/// Write to a pipe given both file descriptors
+fn write_to_pipe(data: u32, parent_fd: RawFd, child_fd: RawFd) {
+    let mut buff = [0; 4];
+    BigEndian::write_u32(&mut buff, data);
+    if unistd::close(parent_fd).is_err() {
+        return;
+    }
+    if unistd::write(child_fd, &buff).is_err() {
+        return;
+    }
+    unistd::close(child_fd).unwrap_or_default();
+}
+
+/// Read from a pipe given both file descriptors
+fn read_from_pipe(parent_fd: RawFd, child_fd: RawFd) -> Option<u32> {
+    let mut buffer = [0; 4];
+    if unistd::close(child_fd).is_err() {
+        return None;
+    }
+    if unistd::read(parent_fd, &mut buffer).is_err() {
+        return None;
+    }
+    if unistd::close(parent_fd).is_err() {
+        return None;
+    }
+    Some(u32::from_be_bytes(buffer))
 }
 
 /// If a [`TerminalAction::OpenFile(file)`] is given, the text editor specified by environment variable `EDITOR`
@@ -145,11 +200,11 @@ fn handle_terminal(cmd: RunCommand, orig_termios: termios::Termios) -> (RawFd, P
 /// This function will panic if both the `EDITOR` and `VISUAL` environment variables are not
 /// set.
 pub fn spawn_terminal(
-    terminal_action: Option<TerminalAction>,
+    terminal_action: TerminalAction,
     orig_termios: termios::Termios,
-) -> (RawFd, Pid) {
+) -> (RawFd, ChildId) {
     let cmd = match terminal_action {
-        Some(TerminalAction::OpenFile(file_to_open)) => {
+        TerminalAction::OpenFile(file_to_open) => {
             if env::var("EDITOR").is_err() && env::var("VISUAL").is_err() {
                 panic!("Can't edit files if an editor is not defined. To fix: define the EDITOR or VISUAL environment variables with the path to your editor (eg. /usr/bin/vim)");
             }
@@ -160,15 +215,13 @@ pub fn spawn_terminal(
                 .into_os_string()
                 .into_string()
                 .expect("Not valid Utf8 Encoding")];
-            RunCommand { command, args }
-        }
-        Some(TerminalAction::RunCommand(command)) => command,
-        None => {
-            let command =
-                PathBuf::from(env::var("SHELL").expect("Could not find the SHELL variable"));
-            let args = vec![];
-            RunCommand { command, args }
+            RunCommand {
+                command,
+                args,
+                cwd: None,
+            }
         }
+        TerminalAction::RunCommand(command) => command,
     };
 
     handle_terminal(cmd, orig_termios)
@@ -214,8 +267,10 @@ impl AsyncReader for RawFdAsyncReader {
 pub trait ServerOsApi: Send + Sync {
     /// Sets the size of the terminal associated to file descriptor `fd`.
     fn set_terminal_size_using_fd(&self, fd: RawFd, cols: u16, rows: u16);
-    /// Spawn a new terminal, with a terminal action.
-    fn spawn_terminal(&self, terminal_action: Option<TerminalAction>) -> (RawFd, Pid);
+    /// Spawn a new terminal, with a terminal action. The returned tuple contains the master file
+    /// descriptor of the forked psuedo terminal and a [ChildId] struct containing process id's for
+    /// the forked child process.
+    fn spawn_terminal(&self, terminal_action: TerminalAction) -> (RawFd, ChildId);
     /// Read bytes from the standard output of the virtual terminal referred to by `fd`.
     fn read_from_tty_stdout(&self, fd: RawFd, buf: &mut [u8]) -> Result<usize, nix::Error>;
     /// Creates an `AsyncReader` that can be used to read from `fd` in an async context
@@ -247,6 +302,8 @@ pub trait ServerOsApi: Send + Sync {
     /// Update the receiver socket for the client
     fn update_receiver(&mut self, stream: LocalSocketStream);
     fn load_palette(&self) -> Palette;
+    /// Returns the current working directory for a given pid
+    fn get_cwd(&self, pid: Pid) -> Option<PathBuf>;
 }
 
 impl ServerOsApi for ServerOsInputOutput {
@@ -255,7 +312,7 @@ impl ServerOsApi for ServerOsInputOutput {
             set_terminal_size_using_fd(fd, cols, rows);
         }
     }
-    fn spawn_terminal(&self, terminal_action: Option<TerminalAction>) -> (RawFd, Pid) {
+    fn spawn_terminal(&self, terminal_action: TerminalAction) -> (RawFd, ChildId) {
         let orig_termios = self.orig_termios.lock().unwrap();
         spawn_terminal(terminal_action, orig_termios.clone())
     }
@@ -336,6 +393,18 @@ impl ServerOsApi for ServerOsInputOutput {
     fn load_palette(&self) -> Palette {
         default_palette()
     }
+    #[cfg(target_os = "macos")]
+    fn get_cwd(&self, pid: Pid) -> Option<PathBuf> {
+        darwin_libproc::pid_cwd(pid.as_raw()).ok()
+    }
+    #[cfg(target_os = "linux")]
+    fn get_cwd(&self, pid: Pid) -> Option<PathBuf> {
+        fs::read_link(format!("/proc/{}/cwd", pid)).ok()
+    }
+    #[cfg(all(not(target_os = "linux"), not(target_os = "macos")))]
+    fn get_cwd(&self, _pid: Pid) -> Option<PathBuf> {
+        None
+    }
 }
 
 impl Clone for Box<dyn ServerOsApi> {
@@ -353,3 +422,13 @@ pub fn get_server_os_input() -> Result<ServerOsInputOutput, nix::Error> {
         send_instructions_to_client: Arc::new(Mutex::new(None)),
     })
 }
+
+/// Process id's for forked terminals
+#[derive(Debug)]
+pub struct ChildId {
+    /// Primary process id of a forked terminal
+    pub primary: Pid,
+    /// Process id of the command running inside the forked terminal, usually a shell. The primary
+    /// field is it's parent process id.
+    pub shell: Option<Pid>,
+}
diff --git a/zellij-server/src/pty.rs b/zellij-server/src/pty.rs
index e28729b7..c6857258 100644
--- a/zellij-server/src/pty.rs
+++ b/zellij-server/src/pty.rs
@@ -1,5 +1,5 @@
 use crate::{
-    os_input_output::{AsyncReader, Pid, ServerOsApi},
+    os_input_output::{AsyncReader, ChildId, ServerOsApi},
     panes::PaneId,
     screen::ScreenInstruction,
     thread_bus::{Bus, ThreadSenders},
@@ -12,14 +12,16 @@ use async_std::{
 };
 use std::{
     collections::HashMap,
+    env,
     os::unix::io::RawFd,
+    path::PathBuf,
     time::{Duration, Instant},
 };
 use zellij_utils::{
     async_std,
     errors::{get_current_ctx, ContextType, PtyContext},
     input::{
-        command::TerminalAction,
+        command::{RunCommand, TerminalAction},
         layout::{Layout, LayoutFromYaml, Run, TabLayout},
     },
     logging::debug_to_file,
@@ -33,6 +35,7 @@ pub(crate) enum PtyInstruction {
     SpawnTerminal(Option<TerminalAction>),
     SpawnTerminalVertically(Option<TerminalAction>),
     SpawnTerminalHorizontally(Option<TerminalAction>),
+    UpdateActivePane(Option<PaneId>),
     NewTab(Option<TerminalAction>, Option<TabLayout>),
     ClosePane(PaneId),
     CloseTab(Vec<PaneId>),
@@ -45,6 +48,7 @@ impl From<&PtyInstruction> for PtyContext {
             PtyInstruction::SpawnTerminal(_) => PtyContext::SpawnTerminal,
             PtyInstruction::SpawnTerminalVertically(_) => PtyContext::SpawnTerminalVertically,
             PtyInstruction::SpawnTerminalHorizontally(_) => PtyContext::SpawnTerminalHorizontally,
+            PtyInstruction::UpdateActivePane(_) => PtyContext::UpdateActivePane,
             PtyInstruction::ClosePane(_) => PtyContext::ClosePane,
             PtyInstruction::CloseTab(_) => PtyContext::CloseTab,
             PtyInstruction::NewTab(..) => PtyContext::NewTab,
@@ -54,8 +58,9 @@ impl From<&PtyInstruction> for PtyContext {
 }
 
 pub(crate) struct Pty {
+    pub active_pane: Option<PaneId>,
     pub bus: Bus<PtyInstruction>,
-    pub id_to_child_pid: HashMap<RawFd, Pid>,
+    pub id_to_child_pid: HashMap<RawFd, ChildId>,
     debug_to_file: bool,
     task_handles: HashMap<RawFd, JoinHandle<()>>,
 }
@@ -86,6 +91,9 @@ pub(crate) fn pty_thread_main(mut pty: Pty, layout: LayoutFromYaml) {
                     .send_to_screen(ScreenInstruction::HorizontalSplit(PaneId::Terminal(pid)))
                     .unwrap();
             }
+            PtyInstruction::UpdateActivePane(pane_id) => {
+                pty.set_active_pane(pane_id);
+            }
             PtyInstruction::NewTab(terminal_action, tab_layout) => {
                 let merged_layout = layout.template.clone().insert_tab_layout(tab_layout);
                 pty.spawn_terminals_for_layout(merged_layout.into(), terminal_action.clone());
@@ -208,14 +216,30 @@ fn stream_terminal_bytes(
 impl Pty {
     pub fn new(bus: Bus<PtyInstruction>, debug_to_file: bool) -> Self {
         Pty {
+            active_pane: None,
             bus,
             id_to_child_pid: HashMap::new(),
             debug_to_file,
             task_handles: HashMap::new(),
         }
     }
+    pub fn get_default_terminal(&self) -> TerminalAction {
+        TerminalAction::RunCommand(RunCommand {
+            args: vec![],
+            command: PathBuf::from(env::var("SHELL").expect("Could not find the SHELL variable")),
+            cwd: self
+                .active_pane
+                .and_then(|pane| match pane {
+                    PaneId::Plugin(..) => None,
+                    PaneId::Terminal(id) => self.id_to_child_pid.get(&id).and_then(|id| id.shell),
+                })
+                .and_then(|id| self.bus.os_input.as_ref().map(|input| input.get_cwd(id)))
+                .flatten(),
+        })
+    }
     pub fn spawn_terminal(&mut self, terminal_action: Option<TerminalAction>) -> RawFd {
-        let (pid_primary, pid_secondary): (RawFd, Pid) = self
+        let terminal_action = terminal_action.unwrap_or_else(|| self.get_default_terminal());
+        let (pid_primary, child_id): (RawFd, ChildId) = self
             .bus
             .os_input
             .as_mut()
@@ -228,7 +252,7 @@ impl Pty {
             self.debug_to_file,
         );
         self.task_handles.insert(pid_primary, task_handle);
-        self.id_to_child_pid.insert(pid_primary, pid_secondary);
+        self.id_to_child_pid.insert(pid_primary, child_id);
         pid_primary
     }
     pub fn spawn_terminals_for_layout(
@@ -236,29 +260,26 @@ impl Pty {
         layout: Layout,
         default_shell: Option<TerminalAction>,
     ) {
+        let default_shell = default_shell.unwrap_or_else(|| self.get_default_terminal());
         let extracted_run_instructions = layout.extract_run_instructions();
         let mut new_pane_pids = vec![];
         for run_instruction in extracted_run_instructions {
             match run_instruction {
                 Some(Run::Command(command)) => {
                     let cmd = TerminalAction::RunCommand(command);
-                    let (pid_primary, pid_secondary): (RawFd, Pid) = self
-                        .bus
-                        .os_input
-                        .as_mut()
-                        .unwrap()
-                        .spawn_terminal(Some(cmd));
-                    self.id_to_child_pid.insert(pid_primary, pid_secondary);
+                    let (pid_primary, child_id): (RawFd, ChildId) =
+                        self.bus.os_input.as_mut().unwrap().spawn_terminal(cmd);
+                    self.id_to_child_pid.insert(pid_primary, child_id);
                     new_pane_pids.push(pid_primary);
                 }
                 None => {
-                    let (pid_primary, pid_secondary): (RawFd, Pid) = self
+                    let (pid_primary, child_id): (RawFd, ChildId) = self
                         .bus
                         .os_input
                         .as_mut()
                         .unwrap()
                         .spawn_terminal(default_shell.clone());
-                    self.id_to_child_pid.insert(pid_primary, pid_secondary);
+                    self.id_to_child_pid.insert(pid_primary, child_id);
                     new_pane_pids.push(pid_primary);
                 }
                 // Investigate moving plugin loading to here.
@@ -285,10 +306,15 @@ impl Pty {
     pub fn close_pane(&mut self, id: PaneId) {
         match id {
             PaneId::Terminal(id) => {
-                let child_pid = self.id_to_child_pid.remove(&id).unwrap();
+                let pids = self.id_to_child_pid.remove(&id).unwrap();
                 let handle = self.task_handles.remove(&id).unwrap();
                 task::block_on(async {
-                    self.bus.os_input.as_mut().unwrap().kill(child_pid).unwrap();
+                    self.bus
+                        .os_input
+                        .as_mut()
+                        .unwrap()
+                        .kill(pids.primary)
+                        .unwrap();
                     let timeout = Duration::from_millis(100);
                     match async_timeout(timeout, handle.cancel()).await {
                         Ok(_) => {}
@@ -297,7 +323,7 @@ impl Pty {
                                 .os_input
                                 .as_mut()
                                 .unwrap()
-                                .force_kill(child_pid)
+                                .force_kill(pids.primary)
                                 .unwrap();
                         }
                     };
@@ -315,6 +341,9 @@ impl Pty {
             self.close_pane(id);
         });
     }
+    pub fn set_active_pane(&mut self, pane_id: Option<PaneId>) {
+        self.active_pane = pane_id;
+    }
 }
 
 impl Drop for Pty {
diff --git a/zellij-server/src/tab.rs b/zellij-server/src/tab.rs
index ba8a8c88..dafb2863 100644
--- a/zellij-server/src/tab.rs
+++ b/zellij-server/src/tab.rs
@@ -295,6 +295,13 @@ impl Tab {
         }
     }
 
+    fn set_active_terminal(&mut self, pane_id: Option<PaneId>) {
+        self.active_terminal = pane_id;
+        self.senders
+            .send_to_pty(PtyInstruction::UpdateActivePane(self.active_terminal))
+            .unwrap();
+    }
+
     pub fn apply_layout(&mut self, layout: Layout, new_pids: Vec<RawFd>, tab_index: usize) {
         // TODO: this should be an attribute on Screen instead of full_screen_ws
         let free_space = PaneGeom::default();
@@ -393,7 +400,7 @@ impl Tab {
         self.set_pane_frames(self.draw_pane_frames);
         // This is the end of the nasty viewport hack...
         // FIXME: Active / new / current terminal, should be pane
-        self.active_terminal = self.panes.iter().map(|(id, _)| id.to_owned()).next();
+        self.set_active_terminal(self.panes.iter().map(|(id, _)| id.to_owned()).next());
         self.render();
     }
     pub fn new_pane(&mut self, pid: PaneId) {
@@ -466,7 +473,7 @@ impl Tab {
                 }
             }
         }
-        self.active_terminal = Some(pid);
+        self.set_active_terminal(Some(pid));
         self.render();
     }
     pub fn horizontal_split(&mut self, pid: PaneId) {
@@ -495,7 +502,7 @@ impl Tab {
                 );
                 active_pane.set_geom(top_winsize);
                 self.panes.insert(pid, Box::new(new_terminal));
-                self.active_terminal = Some(pid);
+                self.set_active_terminal(Some(pid));
                 self.relayout_tab(Direction::Vertical);
                 self.render();
             }
@@ -524,7 +531,7 @@ impl Tab {
                 active_pane.set_geom(left_winsize);
                 self.panes.insert(pid, Box::new(new_terminal));
             }
-            self.active_terminal = Some(pid);
+            self.set_active_terminal(Some(pid));
             self.relayout_tab(Direction::Horizontal);
             self.render();
         }
@@ -1757,16 +1764,16 @@ impl Tab {
         }
         let active_terminal_id = self.get_active_pane_id().unwrap();
         let terminal_ids: Vec<PaneId> = self.get_selectable_panes().map(|(&pid, _)| pid).collect(); // TODO: better, no allocations
-        let first_terminal = terminal_ids.get(0).unwrap();
         let active_terminal_id_position = terminal_ids
             .iter()
             .position(|id| id == &active_terminal_id)
             .unwrap();
-        if let Some(next_terminal) = terminal_ids.get(active_terminal_id_position + 1) {
-            self.active_terminal = Some(*next_terminal);
-        } else {
-            self.active_terminal = Some(*first_terminal);
-        }
+        let active_terminal = terminal_ids
+            .get(active_terminal_id_position + 1)
+            .or_else(|| terminal_ids.get(0))
+            .copied();
+
+        self.set_active_terminal(active_terminal);
         self.render();
     }
     pub fn focus_next_pane(&mut self) {
@@ -1785,16 +1792,17 @@ impl Tab {
                 a_pane.y().cmp(&b_pane.y())
             }
         });
-        let first_pane = panes.get(0).unwrap();
         let active_pane_position = panes
             .iter()
             .position(|(id, _)| *id == &active_pane_id) // TODO: better
             .unwrap();
-        if let Some(next_pane) = panes.get(active_pane_position + 1) {
-            self.active_terminal = Some(*next_pane.0);
-        } else {
-            self.active_terminal = Some(*first_pane.0);
-        }
+
+        let active_terminal = panes
+            .get(active_pane_position + 1)
+            .or_else(|| panes.get(0))
+            .map(|p| *p.0);
+
+        self.set_active_terminal(active_terminal);
         self.render();
     }
     pub fn focus_previous_pane(&mut self) {
@@ -1818,11 +1826,13 @@ impl Tab {
             .iter()
             .position(|(id, _)| *id == &active_pane_id) // TODO: better
             .unwrap();
-        if active_pane_position == 0 {
-            self.active_terminal = Some(*last_pane.0);
+
+        let active_terminal = if active_pane_position == 0 {
+            Some(*last_pane.0)
         } else {
-            self.active_terminal = Some(*panes.get(active_pane_position - 1).unwrap().0);
-        }
+            Some(*panes.get(active_pane_position - 1).unwrap().0)
+        };
+        self.set_active_terminal(active_terminal);
         self.render();
     }
     // returns a boolean that indicates whether the focus moved
@@ -1834,7 +1844,7 @@ impl Tab {
             return false;
         }
         let active_terminal = self.get_active_pane();
-        if let Some(active) = active_terminal {
+        let updated_active_terminal = if let Some(active) = active_terminal {
             let terminals = self.get_selectable_panes();
             let next_index = terminals
                 .enumerate()
@@ -1853,17 +1863,16 @@ impl Tab {
                     let next_active_pane = self.panes.get_mut(&p).unwrap();
                     next_active_pane.set_should_render(true);
 
-                    self.active_terminal = Some(p);
+                    self.set_active_terminal(Some(p));
                     self.render();
                     return true;
                 }
-                None => {
-                    self.active_terminal = Some(active.pid());
-                }
+                None => Some(active.pid()),
             }
         } else {
-            self.active_terminal = Some(active_terminal.unwrap().pid());
-        }
+            Some(active_terminal.unwrap().pid())
+        };
+        self.set_active_terminal(updated_active_terminal);
         false
     }
     pub fn move_focus_down(&mut self) {
@@ -1874,7 +1883,7 @@ impl Tab {
             return;
         }
         let active_terminal = self.get_active_pane();
-        if let Some(active) = active_terminal {
+        let updated_active_terminal = if let Some(active) = active_terminal {
             let terminals = self.get_selectable_panes();
             let next_index = terminals
                 .enumerate()
@@ -1893,15 +1902,14 @@ impl Tab {
                     let next_active_pane = self.panes.get_mut(&p).unwrap();
                     next_active_pane.set_should_render(true);
 
-                    self.active_terminal = Some(p);
-                }
-                None => {
-                    self.active_terminal = Some(active.pid());
+                    Some(p)
                 }
+                None => Some(active.pid()),
             }
         } else {
-            self.active_terminal = Some(active_terminal.unwrap().pid());
-        }
+            Some(active_terminal.unwrap().pid())
+        };
+        self.set_active_terminal(updated_active_terminal);
         self.render();
     }
     pub fn move_focus_up(&mut self) {
@@ -1912,7 +1920,7 @@ impl Tab {
             return;
         }
         let active_terminal = self.get_active_pane();
-        if let Some(active) = active_terminal {
+        let updated_active_terminal = if let Some(active) = active_terminal {
             let terminals = self.get_selectable_panes();
             let next_index = terminals
                 .enumerate()
@@ -1931,15 +1939,14 @@ impl Tab {
                     let next_active_pane = self.panes.get_mut(&p).unwrap();
                     next_active_pane.set_should_render(true);
 
-                    self.active_terminal = Some(p);
-                }
-                None => {
-                    self.active_terminal = Some(active.pid());
+                    Some(p)
                 }
+                None => Some(active.pid()),
             }
         } else {
-            self.active_terminal = Some(active_terminal.unwrap().pid());
-        }
+            Some(active_terminal.unwrap().pid())
+        };
+        self.set_active_terminal(updated_active_terminal);
         self.render();
     }
     // returns a boolean that indicates whether the focus moved
@@ -1951,7 +1958,7 @@ impl Tab {
             return false;
         }
         let active_terminal = self.get_active_pane();
-        if let Some(active) = active_terminal {
+        let updated_active_terminal = if let Some(active) = active_terminal {
             let terminals = self.get_selectable_panes();
             let next_index = terminals
                 .enumerate()
@@ -1970,17 +1977,16 @@ impl Tab {
                     let next_active_pane = self.panes.get_mut(&p).unwrap();
                     next_active_pane.set_should_render(true);
 
-                    self.active_terminal = Some(p);
+                    self.set_active_terminal(Some(p));
                     self.render();
                     return true;
                 }
-                None => {
-                    self.active_terminal = Some(active.pid());
-                }
+                None => Some(active.pid()),
             }
         } else {
-            self.active_terminal = Some(active_terminal.unwrap().pid());
-        }
+            Some(active_terminal.unwrap().pid())
+        };
+        self.set_active_terminal(updated_active_terminal);
         false
     }
     fn horizontal_borders(&self, terminals: &[PaneId]) -> HashSet<usize> {
@@ -1999,6 +2005,7 @@ impl Tab {
             borders
         })
     }
+
     fn panes_to_the_left_between_aligning_borders(&self, id: PaneId) -> Option<Vec<PaneId>> {
         if let Some(terminal) = self.panes.get(&id) {
             let upper_close_border = terminal.y();
@@ -2125,7 +2132,7 @@ impl Tab {
         if let Some(pane) = self.panes.get_mut(&id) {
             pane.set_selectable(selectable);
             if self.get_active_pane_id() == Some(id) && !selectable {
-                self.active_terminal = self.next_active_pane(&self.get_pane_ids())
+                self.set_active_terminal(self.next_active_pane(&self.get_pane_ids()));
             }
         }
         self.render();
@@ -2146,7 +2153,7 @@ impl Tab {
                     self.panes.remove(&id);
                     if self.active_terminal == Some(id) {
                         let next_active_pane = self.next_active_pane(&panes);
-                        self.active_terminal = next_active_pane;
+                        self.set_active_terminal(next_active_pane);
                     }
                     self.relayout_tab(Direction::Horizontal);
                     return;
@@ -2158,7 +2165,7 @@ impl Tab {
                     self.panes.remove(&id);
                     if self.active_terminal == Some(id) {
                         let next_active_pane = self.next_active_pane(&panes);
-                        self.active_terminal = next_active_pane;
+                        self.set_active_terminal(next_active_pane);
                     }
                     self.relayout_tab(Direction::Horizontal);
                     return;
@@ -2170,7 +2177,7 @@ impl Tab {
                     self.panes.remove(&id);
                     if self.active_terminal == Some(id) {
                         let next_active_pane = self.next_active_pane(&panes);
-                        self.active_terminal = next_active_pane;
+                        self.set_active_terminal(next_active_pane);
                     }
                     self.relayout_tab(Direction::Vertical);
                     return;
@@ -2182,7 +2189,7 @@ impl Tab {
                     self.panes.remove(&id);
                     if self.active_terminal == Some(id) {
                         let next_active_pane = self.next_active_pane(&panes);
-                        self.active_terminal = next_active_pane;
+                        self.set_active_terminal(next_active_pane);
                     }
                     self.relayout_tab(Direction::Vertical);
                     return;
@@ -2304,7 +2311,7 @@ impl Tab {
     }
     fn focus_pane_at(&mut self, point: &Position) {
         if let Some(clicked_pane) = self.get_pane_id_at(point) {
-            self.active_terminal = Some(clicked_pane);
+            self.set_active_terminal(Some(clicked_pane));
             self.render();
         }
     }
diff --git a/zellij-server/src/unit/screen_tests.rs b/zellij-server/src/unit/screen_tests.rs
index 95c1b98d..aeea671b 100644
--- a/zellij-server/src/unit/screen_tests.rs
+++ b/zellij-server/src/unit/screen_tests.rs
@@ -1,10 +1,11 @@
 use super::{Screen, ScreenInstruction};
 use crate::zellij_tile::data::{ModeInfo, Palette};
 use crate::{
-    os_input_output::{AsyncReader, Pid, ServerOsApi},
+    os_input_output::{AsyncReader, ChildId, Pid, ServerOsApi},
     thread_bus::Bus,
     SessionState,
 };
+use std::path::PathBuf;
 use std::sync::{Arc, RwLock};
 use zellij_utils::input::command::TerminalAction;
 use zellij_utils::input::layout::LayoutTemplate;
@@ -28,7 +29,7 @@ impl ServerOsApi for FakeInputOutput {
     fn set_terminal_size_using_fd(&self, _fd: RawFd, _cols: u16, _rows: u16) {
         // noop
     }
-    fn spawn_terminal(&self, _file_to_open: Option<TerminalAction>) -> (RawFd, Pid) {
+    fn spawn_terminal(&self, _file_to_open: TerminalAction) -> (RawFd, ChildId) {
         unimplemented!()
     }
     fn read_from_tty_stdout(&self, _fd: RawFd, _buf: &mut [u8]) -> Result<usize, nix::Error> {
@@ -73,6 +74,9 @@ impl ServerOsApi for FakeInputOutput {
     fn load_palette(&self) -> Palette {
         unimplemented!()
     }
+    fn get_cwd(&self, _pid: Pid) -> Option<PathBuf> {
+        unimplemented!()
+    }
 }
 
 fn create_new_screen(size: Size) -> Screen {
diff --git a/zellij-server/src/unit/tab_tests.rs b/zellij-server/src/unit/tab_tests.rs
index ea96df62..de5c1067 100644
--- a/zellij-server/src/unit/tab_tests.rs
+++ b/zellij-server/src/unit/tab_tests.rs
@@ -1,11 +1,12 @@
 use super::Tab;
 use crate::zellij_tile::data::{ModeInfo, Palette};
 use crate::{
-    os_input_output::{AsyncReader, Pid, ServerOsApi},
+    os_input_output::{AsyncReader, ChildId, Pid, ServerOsApi},
     panes::PaneId,
     thread_bus::ThreadSenders,
     SessionState,
 };
+use std::path::PathBuf;
 use std::sync::{Arc, RwLock};
 use zellij_utils::input::layout::LayoutTemplate;
 use zellij_utils::pane_size::Size;
@@ -27,7 +28,7 @@ impl ServerOsApi for FakeInputOutput {
     fn set_terminal_size_using_fd(&self, _fd: RawFd, _cols: u16, _rows: u16) {
         // noop
     }
-    fn spawn_terminal(&self, _file_to_open: Option<TerminalAction>) -> (RawFd, Pid) {
+    fn spawn_terminal(&self, _file_to_open: TerminalAction) -> (RawFd, ChildId) {
         unimplemented!()
     }
     fn read_from_tty_stdout(&self, _fd: RawFd, _buf: &mut [u8]) -> Result<usize, nix::Error> {
@@ -72,6 +73,9 @@ impl ServerOsApi for FakeInputOutput {
     fn load_palette(&self) -> Palette {
         unimplemented!()
     }
+    fn get_cwd(&self, _pid: Pid) -> Option<PathBuf> {
+        unimplemented!()
+    }
 }
 
 fn create_new_tab(size: Size) -> Tab {
diff --git a/zellij-utils/src/errors.rs b/zellij-utils/src/errors.rs
index 65a54c56..87c3bb4d 100644
--- a/zellij-utils/src/errors.rs
+++ b/zellij-utils/src/errors.rs
@@ -237,6 +237,7 @@ pub enum PtyContext {
     SpawnTerminal,
     SpawnTerminalVertically,
     SpawnTerminalHorizontally,
+    UpdateActivePane,
     NewTab,
     ClosePane,
     CloseTab,
diff --git a/zellij-utils/src/input/command.rs b/zellij-utils/src/input/command.rs
index 2054f208..debd5bc5 100644
--- a/zellij-utils/src/input/command.rs
+++ b/zellij-utils/src/input/command.rs
@@ -15,6 +15,8 @@ pub struct RunCommand {
     pub command: PathBuf,
     #[serde(default)]
     pub args: Vec<String>,
+    #[serde(default)]
+    pub cwd: Option<PathBuf>,
 }
 
 /// Intermediate representation
@@ -25,6 +27,8 @@ pub struct RunCommandAction {
     #[serde(default)]
     pub args: Vec<String>,
     #[serde(default)]
+    pub cwd: Option<PathBuf>,
+    #[serde(default)]
     pub direction: Option<Direction>,
 }
 
@@ -33,6 +37,7 @@ impl From<RunCommandAction> for RunCommand {
         RunCommand {
             command: action.command,
             args: action.args,
+            cwd: action.cwd,
         }
     }
 }