feat(tail): follow redirected stdin files

Re-enable test_stdin_redirect_file_follow.

Author: mattsu2020

src/uu/tail/src/follow/watch.rs

@@ -91,6 +91,9 @@ pub struct Observer {
     /// The [`FollowMode`]
     pub follow: Option<FollowMode>,
 
+    /// True when stdin resolves to a tailable file that we should follow.
+    stdin_is_tailable: bool,
+
     /// Indicates whether to use the fallback `polling` method instead of the
     /// platform specific event driven method. Since `use_polling` is subject to
     /// change during runtime it is moved out of [`Settings`].
@@ -101,6 +104,7 @@ pub struct Observer {
     pub files: FileHandling,
 
     pub pid: platform::Pid,
+    stdin_key: Option<PathBuf>,
 }
 
 impl Observer {
@@ -120,14 +124,32 @@ impl Observer {
         Self {
             retry,
             follow,
+            stdin_is_tailable: false,
             use_polling,
             watcher_rx: None,
             orphans: Vec::new(),
             files,
             pid,
+            stdin_key: None,
         }
     }
 
+    pub fn set_stdin_is_tailable(&mut self, value: bool) {
+        self.stdin_is_tailable = value;
+    }
+
+    pub fn stdin_is_tailable(&self) -> bool {
+        self.stdin_is_tailable
+    }
+
+    pub fn set_stdin_key<P: Into<PathBuf>>(&mut self, path: P) {
+        self.stdin_key = Some(path.into());
+    }
+
+    pub fn stdin_key(&self) -> Option<&PathBuf> {
+        self.stdin_key.as_ref()
+    }
+
     pub fn from(settings: &Settings) -> Self {
         Self::new(
             settings.retry,
@@ -146,11 +168,15 @@ impl Observer {
         update_last: bool,
     ) -> UResult<()> {
         if self.follow.is_some() {
-            let path = if path.is_relative() {
+            #[cfg(unix)]
+            let path = if path.is_relative() && !path.is_stdin() {
                 std::env::current_dir()?.join(path)
             } else {
                 path.to_owned()
             };
+            #[cfg(not(unix))]
+            let path = path.to_owned();
+
             let metadata = path.metadata().ok();
             self.files.insert(
                 &path,
@@ -637,6 +663,22 @@ pub fn follow(mut observer: Observer, settings: &Settings) -> UResult<()> {
             paths = observer.files.keys().cloned().collect::<Vec<_>>();
         }
 
+        if observer.stdin_is_tailable() {
+            if let Some(stdin_path) = observer.stdin_key() {
+                if observer.files.contains_key(stdin_path) && !paths.iter().any(|p| p == stdin_path)
+                {
+                    paths.push(stdin_path.clone());
+                }
+            } else {
+                let stdin_path = PathBuf::from(text::DEV_STDIN);
+                if observer.files.contains_key(stdin_path.as_path())
+                    && !paths.iter().any(|p| p.is_stdin())
+                {
+                    paths.push(stdin_path);
+                }
+            }
+        }
+
         // main print loop
         for path in &paths {
             _read_some = observer.files.tail_file(path, settings.verbose)?;

src/uu/tail/src/tail.rs

@@ -100,7 +100,7 @@ fn uu_tail(settings: &Settings) -> UResult<()> {
         the input file is not a FIFO, pipe, or regular file, it is unspecified whether or
         not the -f option shall be ignored.
         */
-        if !settings.has_only_stdin() || settings.pid != 0 {
+        if !settings.has_only_stdin() || settings.pid != 0 || observer.stdin_is_tailable() {
             follow::follow(observer, settings)?;
         }
     }
@@ -227,51 +227,85 @@ fn tail_stdin(
         }
     }
 
-    match input.resolve() {
-        // fifo
-        Some(path) => {
-            let mut stdin_offset = 0;
-            if cfg!(unix) {
-                // Save the current seek position/offset of a stdin redirected file.
-                // This is needed to pass "gnu/tests/tail-2/start-middle.sh"
-                if let Ok(mut stdin_handle) = Handle::stdin() {
-                    if let Ok(offset) = stdin_handle.as_file_mut().stream_position() {
-                        stdin_offset = offset;
-                    }
-                }
+    let resolved_stdin = input.resolve().or_else(resolve_stdin_path);
+
+    if let Some(ref path) = resolved_stdin {
+        let mut stdin_is_seekable_file = false;
+        let mut stdin_offset = 0;
+
+        if let Ok(mut stdin_handle) = Handle::stdin() {
+            if let Ok(offset) = stdin_handle.as_file_mut().stream_position() {
+                stdin_offset = offset;
+            }
+            if let Ok(meta) = stdin_handle.as_file_mut().metadata() {
+                stdin_is_seekable_file = meta.is_file();
             }
+        }
+
+        if !stdin_is_seekable_file {
+            stdin_is_seekable_file = path.metadata().map(|meta| meta.is_file()).unwrap_or(false);
+        }
+
+        if stdin_is_seekable_file {
             tail_file(
                 settings,
                 header_printer,
                 input,
-                &path,
+                path,
                 observer,
                 stdin_offset,
             )?;
+
+            observer.set_stdin_is_tailable(true);
+            observer.set_stdin_key(path.clone());
+            if settings.follow.is_some() {
+                observer.add_path(path, input.display_name.as_str(), None, true)?;
+            }
+            return Ok(());
         }
-        // pipe
-        None => {
+
+        if path.metadata().map(|meta| meta.is_dir()).unwrap_or(false) {
             header_printer.print_input(input);
-            if paths::stdin_is_bad_fd() {
-                set_exit_code(1);
-                show_error!(
-                    "{}",
-                    translate!("tail-error-cannot-fstat", "file" => translate!("tail-stdin-header"), "error" => translate!("tail-bad-fd"))
-                );
-                if settings.follow.is_some() {
-                    show_error!(
-                        "{}",
-                        translate!("tail-error-reading-file", "file" => translate!("tail-stdin-header"), "error" => translate!("tail-bad-fd"))
-                    );
-                }
-            } else {
-                let mut reader = BufReader::new(stdin());
-                unbounded_tail(&mut reader, settings)?;
-                observer.add_stdin(input.display_name.as_str(), Some(Box::new(reader)), true)?;
-            }
+            set_exit_code(1);
+            show_error!(
+                "{}",
+                translate!(
+                    "tail-error-reading-file",
+                    "file" => input.display_name.clone(),
+                    "error" => translate!("tail-is-a-directory")
+                )
+            );
+            return Ok(());
         }
     }
 
+    header_printer.print_input(input);
+    if paths::stdin_is_bad_fd() {
+        set_exit_code(1);
+        show_error!(
+            "{}",
+            translate!(
+                "tail-error-cannot-fstat",
+                "file" => translate!("tail-stdin-header"),
+                "error" => translate!("tail-bad-fd")
+            )
+        );
+        if settings.follow.is_some() {
+            show_error!(
+                "{}",
+                translate!(
+                    "tail-error-reading-file",
+                    "file" => translate!("tail-stdin-header"),
+                    "error" => translate!("tail-bad-fd")
+                )
+            );
+        }
+    } else {
+        let mut reader = BufReader::new(stdin());
+        unbounded_tail(&mut reader, settings)?;
+        observer.add_stdin(input.display_name.as_str(), Some(Box::new(reader)), true)?;
+    }
+
     Ok(())
 }
 
@@ -529,6 +563,39 @@ where
     }
 }
 
+#[cfg(windows)]
+fn resolve_stdin_path() -> Option<PathBuf> {
+    use std::os::windows::io::AsRawHandle;
+    use windows_sys::Win32::Foundation::MAX_PATH;
+    use windows_sys::Win32::Storage::FileSystem::{FILE_NAME_OPENED, GetFinalPathNameByHandleW};
+
+    let handle = std::io::stdin().lock().as_raw_handle();
+    if handle.is_null() {
+        return None;
+    }
+
+    let mut buffer = [0u16; MAX_PATH as usize];
+    let len = unsafe {
+        GetFinalPathNameByHandleW(
+            handle,
+            buffer.as_mut_ptr(),
+            buffer.len() as u32,
+            FILE_NAME_OPENED,
+        )
+    } as usize;
+
+    if len == 0 || len >= buffer.len() {
+        return None;
+    }
+
+    String::from_utf16(&buffer[..len]).ok().map(PathBuf::from)
+}
+
+#[cfg(not(windows))]
+fn resolve_stdin_path() -> Option<PathBuf> {
+    None
+}
+
 #[cfg(test)]
 mod tests {
 

tests/by-util/test_tail.rs

@@ -137,8 +137,6 @@ fn test_stdin_redirect_file() {
 }
 
 #[test]
-// FIXME: the -f test fails with: Assertion failed. Expected 'tail' to be running but exited with status=exit status: 0
-#[ignore = "disabled until fixed"]
 #[cfg(not(target_vendor = "apple"))] // FIXME: for currently not working platforms
 fn test_stdin_redirect_file_follow() {
     // $ echo foo > f