From d6b112a241a67dd5aef3d38c6e297126e5dcd879 Mon Sep 17 00:00:00 2001
From: Kanishk Sachan <yashk242810@gmail.com>
Date: Fri, 17 Jul 2026 16:10:24 +0530
Subject: [PATCH 1/3] head: fix panic when -v header write fails on a long
 filename

When head prints the "==> name <==" header with -v and the filename is
longer than stdout's ~1024-byte buffer, a write error (e.g. /dev/full)
was surfaced inside print_verbatim().unwrap(), causing an abort instead
of a graceful error message.

The two adjacent writes already use `?`, but print_verbatim() wrote to
a fresh io::stdout() handle and its result was unwrapped. Replace it
with stdout.write_all_os(file.as_ref())? so the filename is written
through the same locked handle and any error is propagated like the
surrounding writes.

Fixes #13264
---
 src/uu/head/src/head.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/uu/head/src/head.rs b/src/uu/head/src/head.rs
index 24ff9e5c04..9a1e393b53 100644
--- a/src/uu/head/src/head.rs
+++ b/src/uu/head/src/head.rs
@@ -17,7 +17,7 @@ use std::os::fd::AsFd;
 use std::path::Path;
 use std::path::PathBuf;
 use thiserror::Error;
-use uucore::display::{Quotable, print_verbatim};
+use uucore::display::{OsWrite, Quotable};
 use uucore::error::{FromIo, UError, UResult, USimpleError};
 use uucore::line_ending::LineEnding;
 use uucore::show;
@@ -461,7 +461,7 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
                         writeln!(stdout)?;
                     }
                     write!(stdout, "==> ")?;
-                    print_verbatim(file).unwrap();
+                    stdout.write_all_os(file.as_ref())?;
                     writeln!(stdout, " <==")?;
                     first = false;
                 }

From a5d770a580c3fbf4697bf15b97d1dfc3d3af6179 Mon Sep 17 00:00:00 2001
From: Kanishk Sachan <yashk242810@gmail.com>
Date: Sat, 18 Jul 2026 19:24:47 +0530
Subject: [PATCH 2/3] head: add test for -v header write error (#13264)

---
 tests/by-util/test_head.rs | 20 ++++++++++++++++++++
 1 file changed, 20 insertions(+)

diff --git a/tests/by-util/test_head.rs b/tests/by-util/test_head.rs
index 0f4e9dae5d..e8d319ec19 100644
--- a/tests/by-util/test_head.rs
+++ b/tests/by-util/test_head.rs
@@ -897,6 +897,26 @@ fn test_all_but_last_lines() {
         .stdout_is_fixture("lorem_ipsum_backwards_15_lines.expected");
 }
 
+#[cfg(target_os = "linux")]
+#[test]
+fn test_verbose_header_write_error() {
+    // Before the fix, the filename in the "==> name <==" header was written
+    // with print_verbatim().unwrap(), which panicked on a write error.
+    // With -v, head always prints the header; any write failure must be
+    // reported gracefully rather than causing an abort (#13264).
+    use std::fs::OpenOptions;
+    let dev_full = OpenOptions::new()
+        .write(true)
+        .open("/dev/full")
+        .unwrap();
+    new_ucmd!()
+        .arg("-v")
+        .pipe_in("")
+        .set_stdout(dev_full)
+        .fails()
+        .stderr_contains("No space left on device");
+}
+
 #[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "netbsd"))]
 #[test]
 fn test_write_to_dev_full() {

From e64f32806d50c33518fc089758b172aee60a8524 Mon Sep 17 00:00:00 2001
From: Kanishk Sachan <yashk242810@gmail.com>
Date: Sun, 19 Jul 2026 16:40:06 +0530
Subject: [PATCH 3/3] head: fix cargo fmt style in
 test_verbose_header_write_error

---
 tests/by-util/test_head.rs | 5 +----
 1 file changed, 1 insertion(+), 4 deletions(-)

diff --git a/tests/by-util/test_head.rs b/tests/by-util/test_head.rs
index e8d319ec19..53657065da 100644
--- a/tests/by-util/test_head.rs
+++ b/tests/by-util/test_head.rs
@@ -905,10 +905,7 @@ fn test_verbose_header_write_error() {
     // With -v, head always prints the header; any write failure must be
     // reported gracefully rather than causing an abort (#13264).
     use std::fs::OpenOptions;
-    let dev_full = OpenOptions::new()
-        .write(true)
-        .open("/dev/full")
-        .unwrap();
+    let dev_full = OpenOptions::new().write(true).open("/dev/full").unwrap();
     new_ucmd!()
         .arg("-v")
         .pipe_in("")