From cf50952325495889d75165acb7e6c1be37a68c4d Mon Sep 17 00:00:00 2001
From: Jan Verbeek <jan.verbeek@posteo.nl>
Date: Mon, 31 Mar 2025 13:19:55 +0200
Subject: [PATCH] tail: Flush `BufWriter`

---
 src/uu/tail/src/chunks.rs       |  2 +-
 src/uu/tail/src/follow/files.rs |  8 ++++----
 src/uu/tail/src/tail.rs         |  4 ++--
 tests/by-util/test_tail.rs      | 10 ++++++++++
 4 files changed, 17 insertions(+), 7 deletions(-)

diff --git a/src/uu/tail/src/chunks.rs b/src/uu/tail/src/chunks.rs
index e8ee761ed..b9bf54594 100644
--- a/src/uu/tail/src/chunks.rs
+++ b/src/uu/tail/src/chunks.rs
@@ -319,7 +319,7 @@ impl BytesChunkBuffer {
         Ok(())
     }
 
-    pub fn print(&self, mut writer: impl Write) -> UResult<()> {
+    pub fn print(&self, writer: &mut impl Write) -> UResult<()> {
         for chunk in &self.chunks {
             writer.write_all(chunk.get_buffer())?;
         }
diff --git a/src/uu/tail/src/follow/files.rs b/src/uu/tail/src/follow/files.rs
index 21af5eb28..509d84d84 100644
--- a/src/uu/tail/src/follow/files.rs
+++ b/src/uu/tail/src/follow/files.rs
@@ -12,7 +12,7 @@ use crate::text;
 use std::collections::HashMap;
 use std::collections::hash_map::Keys;
 use std::fs::{File, Metadata};
-use std::io::{BufRead, BufReader, BufWriter, stdout};
+use std::io::{BufRead, BufReader, BufWriter, Write, stdout};
 use std::path::{Path, PathBuf};
 use uucore::error::UResult;
 
@@ -146,9 +146,9 @@ impl FileHandling {
                 self.header_printer.print(display_name.as_str());
             }
 
-            let stdout = stdout();
-            let writer = BufWriter::new(stdout.lock());
-            chunks.print(writer)?;
+            let mut writer = BufWriter::new(stdout().lock());
+            chunks.print(&mut writer)?;
+            writer.flush()?;
 
             self.last.replace(path.to_owned());
             self.update_metadata(path, None);
diff --git a/src/uu/tail/src/tail.rs b/src/uu/tail/src/tail.rs
index 11af1a685..3cbc34f8d 100644
--- a/src/uu/tail/src/tail.rs
+++ b/src/uu/tail/src/tail.rs
@@ -399,8 +399,7 @@ fn bounded_tail(file: &mut File, settings: &Settings) {
 }
 
 fn unbounded_tail<T: Read>(reader: &mut BufReader<T>, settings: &Settings) -> UResult<()> {
-    let stdout = stdout();
-    let mut writer = BufWriter::new(stdout.lock());
+    let mut writer = BufWriter::new(stdout().lock());
     match &settings.mode {
         FilterMode::Lines(Signum::Negative(count), sep) => {
             let mut chunks = chunks::LinesChunkBuffer::new(*sep, *count);
@@ -459,6 +458,7 @@ fn unbounded_tail<T: Read>(reader: &mut BufReader<T>, settings: &Settings) -> UR
         }
         _ => {}
     }
+    writer.flush()?;
     Ok(())
 }
 
diff --git a/tests/by-util/test_tail.rs b/tests/by-util/test_tail.rs
index 76a93b7c6..ff0bc7141 100644
--- a/tests/by-util/test_tail.rs
+++ b/tests/by-util/test_tail.rs
@@ -4847,3 +4847,13 @@ fn test_child_when_run_with_stderr_to_stdout() {
         .fails()
         .stdout_only(expected_stdout);
 }
+
+#[cfg(target_os = "linux")]
+#[test]
+fn test_failed_write_is_reported() {
+    new_ucmd!()
+        .pipe_in("hello")
+        .set_stdout(std::fs::File::create("/dev/full").unwrap())
+        .fails()
+        .stderr_is("tail: No space left on device\n");
+}