From 2a9b4eaf90930128cd4b3cdba0796b56512a4d7a Mon Sep 17 00:00:00 2001
From: weili <541602953@qq.com>
Date: Fri, 3 Jul 2026 07:53:02 +0000
Subject: [PATCH] head: don't panic on a write error while printing a verbose
 header

The verbose `==> name <==` header wrote the filename with
`print_verbatim(file).unwrap()`, while the surrounding writes use `?`.
When the filename is longer than the stdout buffer, `write_all` flushes
mid-write, so a write error (e.g. stdout on a full device) is raised
inside the `unwrap` and aborts the process instead of being reported.

Propagate the error with `?` like the neighbouring header writes, so a
write failure exits non-zero with a message instead of panicking,
regardless of filename length.
---
 src/uu/head/src/head.rs    |  2 +-
 tests/by-util/test_head.rs | 16 ++++++++++++++++
 2 files changed, 17 insertions(+), 1 deletion(-)

diff --git a/src/uu/head/src/head.rs b/src/uu/head/src/head.rs
index 955b3334dfd..0fc28fb6911 100644
--- a/src/uu/head/src/head.rs
+++ b/src/uu/head/src/head.rs
@@ -460,7 +460,7 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
                         writeln!(stdout)?;
                     }
                     write!(stdout, "==> ")?;
-                    print_verbatim(file).unwrap();
+                    print_verbatim(file)?;
                     writeln!(stdout, " <==")?;
                     first = false;
                 }
diff --git a/tests/by-util/test_head.rs b/tests/by-util/test_head.rs
index 0f4e9dae5dd..e2edbed6c09 100644
--- a/tests/by-util/test_head.rs
+++ b/tests/by-util/test_head.rs
@@ -919,6 +919,22 @@ fn test_write_to_dev_full() {
     }
 }
 
+#[cfg(any(target_os = "linux", target_os = "freebsd", target_os = "netbsd"))]
+#[test]
+fn test_verbose_header_long_name_write_error_no_panic() {
+    use std::fs::OpenOptions;
+
+    let dev_full = OpenOptions::new().write(true).open("/dev/full").unwrap();
+
+    let long_name = format!("/dev/{}null", "./".repeat(512));
+
+    new_ucmd!()
+        .args(&["-v", &long_name])
+        .set_stdout(dev_full)
+        .fails_with_code(1)
+        .stderr_contains("head: No space left on device");
+}
+
 #[test]
 #[cfg(target_os = "linux")]
 #[cfg_attr(wasi_runner, ignore = "WASI: argv/filenames must be valid UTF-8")]