Spawn children from foreground working directory

To allow applications spawned by Alacritty to make use of the
shell/foreground process' working directory, it is now set for all new
processes spawned by Alacritty on Unix platforms.

Fixes #5616.

Co-authored-by: Christian Duerr <contact@christianduerr.com>

1 files changed, 40 insertions, 5 deletions

diff --git a/alacritty/src/daemon.rs b/alacritty/src/daemon.rs
index b199c353..4b95cb6b 100644
--- a/alacritty/src/daemon.rs
+++ b/alacritty/src/daemon.rs
@@ -1,16 +1,28 @@
+#[cfg(not(windows))]
+use std::error::Error;
 use std::ffi::OsStr;
 use std::fmt::Debug;
+#[cfg(not(any(target_os = "macos", windows)))]
+use std::fs;
 use std::io;
 #[cfg(not(windows))]
 use std::os::unix::process::CommandExt;
 #[cfg(windows)]
 use std::os::windows::process::CommandExt;
+#[cfg(not(windows))]
+use std::path::PathBuf;
 use std::process::{Command, Stdio};
 
 use log::{debug, warn};
 #[cfg(windows)]
 use winapi::um::winbase::{CREATE_NEW_PROCESS_GROUP, CREATE_NO_WINDOW};
 
+#[cfg(not(windows))]
+use alacritty_terminal::tty;
+
+#[cfg(target_os = "macos")]
+use crate::macos;
+
 /// Start the daemon and log error on failure.
 pub fn start_daemon<I, S>(program: &str, args: I)
 where
@@ -43,18 +55,41 @@ where
         .map(|_| ())
 }
 
+/// Get working directory of controlling process.
+#[cfg(not(windows))]
+pub fn foreground_process_path() -> Result<PathBuf, Box<dyn Error>> {
+    let mut pid = unsafe { libc::tcgetpgrp(tty::master_fd()) };
+    if pid < 0 {
+        pid = tty::child_pid();
+    }
+
+    #[cfg(not(any(target_os = "macos", target_os = "freebsd")))]
+    let link_path = format!("/proc/{}/cwd", pid);
+    #[cfg(target_os = "freebsd")]
+    let link_path = format!("/compat/linux/proc/{}/cwd", pid);
+
+    #[cfg(not(target_os = "macos"))]
+    let cwd = fs::read_link(link_path)?;
+
+    #[cfg(target_os = "macos")]
+    let cwd = macos::proc::cwd(pid)?;
+
+    Ok(cwd)
+}
+
 #[cfg(not(windows))]
 fn spawn_daemon<I, S>(program: &str, args: I) -> io::Result<()>
 where
     I: IntoIterator<Item = S> + Copy,
     S: AsRef<OsStr>,
 {
+    let mut command = Command::new(program);
+    command.args(args).stdin(Stdio::null()).stdout(Stdio::null()).stderr(Stdio::null());
+    if let Ok(cwd) = foreground_process_path() {
+        command.current_dir(cwd);
+    }
     unsafe {
-        Command::new(program)
-            .args(args)
-            .stdin(Stdio::null())
-            .stdout(Stdio::null())
-            .stderr(Stdio::null())
+        command
             .pre_exec(|| {
                 match libc::fork() {
                     -1 => return Err(io::Error::last_os_error()),