tail: handle broken pipe gracefully

src/uu/tail/src/tail.rs

@@ -40,6 +40,15 @@ use uucore::{show, show_error};
 
 #[uucore::main]
 pub fn uumain(args: impl uucore::Args) -> UResult<()> {
+    // When we receive a SIGPIPE signal, we want to terminate the process so
+    // that we don't print any error messages to stderr. Rust ignores SIGPIPE
+    // (see https://github.com/rust-lang/rust/issues/62569), so we restore it's
+    // default action here.
+    #[cfg(not(target_os = "windows"))]
+    unsafe {
+        libc::signal(libc::SIGPIPE, libc::SIG_DFL);
+    }
+
     let settings = parse_args(args)?;
 
     settings.check_warnings();
@@ -541,7 +550,16 @@ fn unbounded_tail<T: Read>(reader: &mut BufReader<T>, settings: &Settings) -> UR
         }
         _ => {}
     }
+    #[cfg(not(target_os = "windows"))]
     writer.flush()?;
+
+    // SIGPIPE is not available on Windows.
+    #[cfg(target_os = "windows")]
+    writer.flush().inspect_err(|err| {
+        if err.kind() == ErrorKind::BrokenPipe {
+            std::process::exit(13);
+        }
+    })?;
     Ok(())
 }
 

tests/by-util/test_tail.rs

@@ -4897,6 +4897,19 @@ fn test_when_piped_input_then_no_broken_pipe() {
     }
 }
 
+#[test]
+fn test_when_output_closed_then_no_broken_pie() {
+    let mut cmd = new_ucmd!();
+    let mut child = cmd
+        .args(&[FOOBAR_TXT])
+        .set_stdout(Stdio::piped())
+        .run_no_wait();
+    // Dropping the stdout should not lead to an error.
+    // The "Broken pipe" error should be silently ignored.
+    child.close_stdout();
+    child.wait().unwrap().fails_silently();
+}
+
 #[test]
 fn test_child_when_run_with_stderr_to_stdout() {
     let ts = TestScenario::new("tail");

tests/uutests/src/lib/util.rs

@@ -695,7 +695,11 @@ impl CmdResult {
     #[track_caller]
     pub fn fails_silently(&self) -> &Self {
         assert!(!self.succeeded());
-        assert!(self.stderr.is_empty());
+        assert!(
+            self.stderr.is_empty(),
+            "Expected stderr to be empty, but it's:\n{}",
+            self.stderr_str()
+        );
         self
     }