expose the tty name associated with a pane

codec/src/lib.rs

@@ -431,7 +431,7 @@ macro_rules! pdu {
 /// The overall version of the codec.
 /// This must be bumped when backwards incompatible changes
 /// are made to the types and protocol.
-pub const CODEC_VERSION: usize = 40;
+pub const CODEC_VERSION: usize = 41;
 
 // Defines the Pdu enum.
 // Each struct has an explicit identifying number.

docs/changelog.md

@@ -64,6 +64,9 @@ As features stabilize some brief notes about them will accumulate here.
 * [wezterm cli rename-workspace](cli/cli/rename-workspace.md). #2787
 * [wezterm.mux.rename_workspace](config/lua/wezterm.mux/rename_workspace.md). #2787
 * [wezterm cli get-pane-direction](cli/cli/get-pane-direction.md)
+* [pane:get_tty_name()](config/lua/pane/get_tty_name.md) and
+  [PaneInformation.tty_name](config/lua/PaneInformation.md) to reason about the
+  tty name on local unix systems.
 
 #### Fixed
 * mux: Stale remote window mapping could prevent spawning new tabs in remote domain. #2759

docs/config/lua/PaneInformation.md

@@ -126,3 +126,7 @@ end)
 return config
 ```
 
+{{since('nightly')}}
+
+The `tty_name` field returns the tty name with the same constraints as described
+in [pane:get_tty_name()](../pane/get_tty_name.md).

docs/config/lua/pane/get_tty_name.md

@@ -0,0 +1,27 @@
+# `pane:get_tty_name()`
+
+{{since('nightly')}}
+
+Returns the tty device name, or `nil` if the name is unavailable.
+
+* This information is only available for local panes.  Multiplexer panes do not report this information.  Similarly, if you are using eg: `ssh` to connect to a remote host, you won't be able to access the name of the remote process that is running.
+* This information is only available on unix systems.  Windows systems do not have an equivalent concept.
+
+This example sets the right status to show the tty name:
+
+```lua
+local wezterm = require 'wezterm'
+
+wezterm.on('update-status', function(window, pane)
+  local tty = pane:get_tty_name()
+  if tty then
+    window:set_right_status(tty)
+  else
+    window:set_right_status ''
+  end
+end)
+
+return {}
+```
+
+

lua-api-crates/mux/src/pane.rs

@@ -403,6 +403,12 @@ impl UserData for MuxPane {
             tab.set_active_pane(&pane);
             Ok(())
         });
+
+        methods.add_method("get_tty_name", move |_lua, this, ()| {
+            let mux = Mux::get();
+            let pane = this.resolve(&mux)?;
+            Ok(pane.tty_name())
+        });
     }
 }
 

mux/src/localpane.rs

@@ -457,6 +457,11 @@ impl Pane for LocalPane {
             .or_else(|| self.divine_current_working_dir())
     }
 
+    fn tty_name(&self) -> Option<String> {
+        let name = self.pty.lock().tty_name()?;
+        Some(name.to_string_lossy().into_owned())
+    }
+
     fn get_foreground_process_info(&self) -> Option<LocalProcessInfo> {
         #[cfg(unix)]
         if let Some(pid) = self.pty.lock().process_group_leader() {

mux/src/pane.rs

@@ -345,6 +345,10 @@ pub trait Pane: Downcast + Send + Sync {
         None
     }
 
+    fn tty_name(&self) -> Option<String> {
+        None
+    }
+
     fn trickle_paste(&self, text: String) -> anyhow::Result<()> {
         if text.len() <= PASTE_CHUNK_SIZE {
             // Send it all now

mux/src/ssh.rs

@@ -996,6 +996,11 @@ impl portable_pty::MasterPty for WrappedSshPty {
     fn as_raw_fd(&self) -> Option<std::os::fd::RawFd> {
         None
     }
+
+    #[cfg(unix)]
+    fn tty_name(&self) -> Option<std::path::PathBuf> {
+        None
+    }
 }
 
 impl std::io::Write for PtyWriter {

mux/src/tab.rs

@@ -277,6 +277,7 @@ fn pane_tree(
                 physical_top: dims.physical_top,
                 left_col,
                 top_row,
+                tty_name: pane.tty_name(),
             })
         }
     }
@@ -2110,6 +2111,7 @@ pub struct PaneEntry {
     pub physical_top: StableRowIndex,
     pub top_row: usize,
     pub left_col: usize,
+    pub tty_name: Option<String>,
 }
 
 #[derive(Deserialize, Clone, Serialize, PartialEq, Debug)]

mux/src/tmux_pty.rs

@@ -161,4 +161,9 @@ impl MasterPty for TmuxPty {
     fn as_raw_fd(&self) -> Option<std::os::fd::RawFd> {
         None
     }
+
+    #[cfg(unix)]
+    fn tty_name(&self) -> Option<std::path::PathBuf> {
+        None
+    }
 }

pty/src/lib.rs

@@ -113,6 +113,9 @@ pub trait MasterPty {
     #[cfg(unix)]
     fn as_raw_fd(&self) -> Option<unix::RawFd>;
 
+    #[cfg(unix)]
+    fn tty_name(&self) -> Option<std::path::PathBuf>;
+
     /// If applicable to the type of the tty, return the termios
     /// associated with the stream
     #[cfg(unix)]

pty/src/serial.rs

@@ -17,6 +17,7 @@ use serial::{
 use std::cell::RefCell;
 use std::ffi::{OsStr, OsString};
 use std::io::{Read, Result as IoResult, Write};
+use std::path::PathBuf;
 use std::sync::{Arc, Mutex};
 use std::time::Duration;
 
@@ -245,6 +246,11 @@ impl MasterPty for Master {
     fn as_raw_fd(&self) -> Option<crate::unix::RawFd> {
         None
     }
+
+    #[cfg(unix)]
+    fn tty_name(&self) -> Option<PathBuf> {
+        None
+    }
 }
 
 struct Reader {

pty/src/unix.rs

@@ -5,9 +5,12 @@ use anyhow::{bail, Error};
 use filedescriptor::FileDescriptor;
 use libc::{self, winsize};
 use std::cell::RefCell;
+use std::ffi::OsStr;
 use std::io::{Read, Write};
+use std::os::unix::ffi::OsStrExt;
 use std::os::unix::io::{AsRawFd, FromRawFd};
 use std::os::unix::process::CommandExt;
+use std::path::PathBuf;
 use std::{io, mem, ptr};
 
 pub use std::os::unix::io::RawFd;
@@ -42,9 +45,12 @@ fn openpty(size: PtySize) -> anyhow::Result<(UnixMasterPty, UnixSlavePty)> {
         bail!("failed to openpty: {:?}", io::Error::last_os_error());
     }
 
+    let tty_name = tty_name(slave);
+
     let master = UnixMasterPty {
         fd: PtyFd(unsafe { FileDescriptor::from_raw_fd(master) }),
         took_writer: RefCell::new(false),
+        tty_name,
     };
     let slave = UnixSlavePty {
         fd: PtyFd(unsafe { FileDescriptor::from_raw_fd(slave) }),
@@ -98,6 +104,33 @@ impl Read for PtyFd {
     }
 }
 
+fn tty_name(fd: RawFd) -> Option<PathBuf> {
+    let mut buf = vec![0 as std::ffi::c_char; 128];
+
+    loop {
+        let res = unsafe { libc::ttyname_r(fd, buf.as_mut_ptr(), buf.len()) };
+
+        if res == libc::ERANGE {
+            if buf.len() > 64 * 1024 {
+                // on macOS, if the buf is "too big", ttyname_r can
+                // return ERANGE, even though that is supposed to
+                // indicate buf is "too small".
+                return None;
+            }
+            buf.resize(buf.len() * 2, 0 as std::ffi::c_char);
+            continue;
+        }
+
+        return if res == 0 {
+            let cstr = unsafe { std::ffi::CStr::from_ptr(buf.as_ptr()) };
+            let osstr = OsStr::from_bytes(cstr.to_bytes());
+            Some(PathBuf::from(osstr))
+        } else {
+            None
+        };
+    }
+}
+
 /// On Big Sur, Cocoa leaks various file descriptors to child processes,
 /// so we need to make a pass through the open descriptors beyond just the
 /// stdio descriptors and close them all out.
@@ -269,6 +302,7 @@ impl PtyFd {
 struct UnixMasterPty {
     fd: PtyFd,
     took_writer: RefCell<bool>,
+    tty_name: Option<PathBuf>,
 }
 
 /// Represents the slave end of a pty.
@@ -332,6 +366,10 @@ impl MasterPty for UnixMasterPty {
         Some(self.fd.0.as_raw_fd())
     }
 
+    fn tty_name(&self) -> Option<PathBuf> {
+        self.tty_name.clone()
+    }
+
     fn process_group_leader(&self) -> Option<libc::pid_t> {
         match unsafe { libc::tcgetpgrp(self.fd.0.as_raw_fd()) } {
             pid if pid > 0 => Some(pid),

wezterm-gui/src/termwindow/mod.rs

@@ -289,6 +289,15 @@ impl UserData for PaneInformation {
                 None => Ok("".to_string()),
             }
         });
+        fields.add_field_method_get("tty_name", |_, this| {
+            let mut name = None;
+            if let Some(mux) = Mux::try_get() {
+                if let Some(pane) = mux.get_pane(this.pane_id) {
+                    name = pane.tty_name();
+                }
+            }
+            Ok(name)
+        });
         fields.add_field_method_get("current_working_dir", |_, this| {
             let mut name = None;
             if let Some(mux) = Mux::try_get() {

wezterm-ssh/src/pty.rs

@@ -82,6 +82,11 @@ impl portable_pty::MasterPty for SshPty {
     fn as_raw_fd(&self) -> Option<std::os::fd::RawFd> {
         None
     }
+
+    #[cfg(unix)]
+    fn tty_name(&self) -> Option<std::path::PathBuf> {
+        None
+    }
 }
 
 #[derive(Debug)]

wezterm/src/cli/list.rs

@@ -138,6 +138,7 @@ struct CliListResultItem {
     window_title: String,
     is_active: bool,
     is_zoomed: bool,
+    tty_name: Option<String>,
 }
 
 impl CliListResultItem {
@@ -155,6 +156,7 @@ impl CliListResultItem {
             top_row,
             is_active_pane,
             is_zoomed_pane,
+            tty_name,
             size:
                 TerminalSize {
                     rows,
@@ -194,6 +196,7 @@ impl CliListResultItem {
             window_title: window_title.to_string(),
             is_active: is_active_pane,
             is_zoomed: is_zoomed_pane,
+            tty_name,
         }
     }
 }