chmod: fail if the operand list is empty

src/uu/chmod/src/chmod.rs

@@ -98,6 +98,10 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         Some(cmode)
     };
 
+    if files.is_empty() {
+        crash!(1, "missing operand");
+    }
+
     let chmoder = Chmoder {
         changes,
         quiet,

tests/by-util/test_chmod.rs

@@ -523,3 +523,12 @@ fn test_chmod_keep_setgid() {
         assert_eq!(at.metadata("dir").permissions().mode(), to);
     }
 }
+
+#[test]
+fn test_no_operands() {
+    new_ucmd!()
+        .arg("777")
+        .fails()
+        .code_is(1)
+        .stderr_is("chmod: missing operand");
+}