fix(head): check the whether file exists before unwrap (#1858)

closes https://github.com/uutils/coreutils/issues/1800

src/uu/head/src/head.rs

@@ -149,6 +149,13 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
             first_time = false;
 
             let path = Path::new(file);
+            if path.is_dir() || !path.metadata().is_ok() {
+                eprintln!(
+                    "cannot open '{}' for reading: No such file or directory",
+                    &path.to_str().unwrap()
+                );
+                continue;
+            }
             let reader = File::open(&path).unwrap();
             let mut buffer = BufReader::new(reader);
             if !head(&mut buffer, &settings) {

tests/by-util/test_head.rs

@@ -167,3 +167,15 @@ fn test_bug_in_negative_zero_lines() {
         //GNU Head returns "a\nb\n"
         .stdout_is("");
 }
+
+#[test]
+fn test_no_such_file_or_directory() {
+    let result = new_ucmd!().arg("no_such_file.toml").run();
+
+    assert_eq!(
+        true,
+        result
+            .stderr
+            .contains("cannot open 'no_such_file.toml' for reading: No such file or directory")
+    )
+}