head: fix error message when input is a directory (#11541)

* head: fix error message when input is a directory

* head: check for directory before trying to open

src/uu/head/src/head.rs

@@ -13,10 +13,10 @@ use std::io::{self, BufWriter, Read, Seek, SeekFrom, Write};
 use std::num::TryFromIntError;
 #[cfg(unix)]
 use std::os::fd::AsFd;
-use std::path::PathBuf;
+use std::path::{Path, PathBuf};
 use thiserror::Error;
 use uucore::display::{Quotable, print_verbatim};
-use uucore::error::{FromIo, UError, UResult};
+use uucore::error::{FromIo, UError, UResult, USimpleError};
 use uucore::line_ending::LineEnding;
 use uucore::translate;
 use uucore::{format_usage, show};
@@ -510,6 +510,13 @@ fn uu_head(options: &HeadOptions) -> UResult<()> {
 
             Ok(())
         } else {
+            if Path::new(file).is_dir() {
+                show!(USimpleError::new(
+                    1,
+                    translate!("head-error-reading-file", "name" => file.quote(), "err" => "Is a directory")
+                ));
+                continue;
+            }
             let mut file_handle = match File::open(file) {
                 Ok(f) => f,
                 Err(err) => {

tests/by-util/test_head.rs

@@ -911,3 +911,11 @@ fn test_head_non_utf8_paths() {
     assert!(output.contains("line3"));
 }
 // Test that head handles non-UTF-8 file names without crashing
+
+#[test]
+fn test_do_not_attempt_to_read_a_directory() {
+    new_ucmd!()
+        .arg(".")
+        .fails_with_code(1)
+        .stderr_contains("error reading '.'");
+}