tty: support printing msys2 tty path

Author: ChrisDenton

Cargo.lock

@@ -27,6 +27,12 @@ fluent = { workspace = true }
 [target.'cfg(unix)'.dependencies]
 rustix = { workspace = true, features = ["fs", "termios"] }
 
+[target.'cfg(windows)'.dependencies]
+windows-sys = { workspace = true, features = [
+  "Win32_Storage_FileSystem",
+  "Win32_Foundation",
+] }
+
 [[bin]]
 name = "tty"
 path = "src/main.rs"

src/uu/tty/Cargo.toml

@@ -58,11 +58,20 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
         writeln!(stdout, "{}", translate!("tty-not-a-tty"))
     };
     #[cfg(target_os = "windows")]
-    let write_result = if std::io::stdin().is_terminal() {
-        writeln!(stdout, r"\\.\CON")
-    } else {
-        set_exit_code(1);
-        writeln!(stdout, "{}", translate!("tty-not-a-tty"))
+    let write_result = {
+        use std::os::windows::io::AsHandle;
+        let stdin = std::io::stdin();
+        let stdin_handle = stdin.as_handle();
+        if stdin_handle.is_terminal() {
+            if let Some(name) = file_name(stdin_handle) {
+                writeln!(stdout, "{name}")
+            } else {
+                writeln!(stdout, r"\\.\CON")
+            }
+        } else {
+            set_exit_code(1);
+            writeln!(stdout, "{}", translate!("tty-not-a-tty"))
+        }
     };
 
     if write_result.is_err() || stdout.flush().is_err() {
@@ -74,6 +83,42 @@ pub fn uumain(args: impl uucore::Args) -> UResult<()> {
     Ok(())
 }
 
+#[cfg(target_os = "windows")]
+fn file_name(handle: std::os::windows::io::BorrowedHandle) -> Option<String> {
+    use std::mem::MaybeUninit;
+    use std::os::windows::io::AsRawHandle;
+    use windows_sys::Win32::Foundation::MAX_PATH;
+    use windows_sys::Win32::Storage::FileSystem::{FileNameInfo, GetFileInformationByHandleEx};
+    // Manually define FILE_NAME_INFO so we can more easily construct a stack buffer.
+    #[repr(C)]
+    #[allow(non_snake_case)]
+    struct FILE_NAME_INFO {
+        FileNameLength: u32,
+        FileName: [MaybeUninit<u16>; MAX_PATH as usize],
+    }
+    let mut name = FILE_NAME_INFO {
+        FileNameLength: 0,
+        FileName: [MaybeUninit::uninit(); _],
+    };
+    unsafe {
+        let result = GetFileInformationByHandleEx(
+            handle.as_raw_handle(),
+            FileNameInfo,
+            (&raw mut name).cast(),
+            size_of::<FILE_NAME_INFO>() as u32,
+        );
+        if result == 0 {
+            None
+        } else {
+            let name = name.FileName.get(..name.FileNameLength as usize / 2)?;
+            // SAFETY: all elements up to FileNameLength have been initialized
+            let name: &[u16] = &*(std::ptr::from_ref::<[MaybeUninit<u16>]>(name) as *const [u16]);
+            // This should never fail for a valid msys terminal because they use ASCII names.
+            String::from_utf16(name).ok()
+        }
+    }
+}
+
 pub fn uu_app() -> Command {
     let cmd = Command::new("tty")
         .version(uucore::crate_version!())