find: print a trailing backslash in -printf

src/find/matchers/printf.rs

@@ -169,6 +169,14 @@ impl FormatStringParser<'_> {
         const OCTAL_LEN: usize = 3;
         const OCTAL_RADIX: u32 = 8;
 
+        if self.string.is_empty() {
+            eprintln!(
+                "{}: warning: escape `\\' followed by nothing at all",
+                crate::find::program_name()
+            );
+            return Ok(FormatComponent::Literal("\\".to_owned()));
+        }
+
         // Try parsing an octal sequence first.
         let first = self.front()?;
         if first.is_digit(OCTAL_RADIX) {
@@ -792,7 +800,17 @@ mod tests {
             FormatString::parse("\\X").unwrap().components,
             vec![FormatComponent::Literal("\\X".to_owned())]
         );
-        assert!(FormatString::parse("\\").is_err());
+        assert_eq!(
+            FormatString::parse("\\").unwrap().components,
+            vec![FormatComponent::Literal("\\".to_owned())]
+        );
+        assert_eq!(
+            FormatString::parse("abc\\").unwrap().components,
+            vec![
+                FormatComponent::Literal("abc".to_owned()),
+                FormatComponent::Literal("\\".to_owned()),
+            ]
+        );
     }
 
     #[test]

tests/test_find.rs

@@ -768,6 +768,35 @@ fn find_printf_unrecognized_escape_prints_literally() {
         .stderr_contains("unrecognized escape '\\€'");
 }
 
+#[test]
+fn find_printf_trailing_backslash() {
+    let expected_warning = b"find: warning: escape `\\' followed by nothing at all\n";
+    ucmd()
+        .args(&["test_data/simple", "-maxdepth", "0", "-printf", "x\\"])
+        .succeeds()
+        .stdout_is_bytes(b"x\\")
+        .stderr_is_bytes(expected_warning);
+
+    let temp_dir = Builder::new()
+        .prefix("find_fprintf_backslash_")
+        .tempdir()
+        .unwrap();
+    let file = temp_dir.path().join("out");
+    ucmd()
+        .args(&[
+            "test_data/simple",
+            "-maxdepth",
+            "0",
+            "-fprintf",
+            file.to_str().unwrap(),
+            "x\\",
+        ])
+        .succeeds()
+        .stdout_is_bytes(b"")
+        .stderr_is_bytes(expected_warning);
+    assert_eq!(fs::read(file).unwrap(), b"x\\");
+}
+
 #[test]
 fn find_printf_width_too_large() {
     ucmd()