From 63607367d3835706e9e81c6f7e28e103c5e92685 Mon Sep 17 00:00:00 2001
From: fixfon <12512757+fixfon@users.noreply.github.com>
Date: Fri, 23 Oct 2026 12:05:33 +0300
Subject: [PATCH] chmod: accept modes like -=r, -+x and -,u+x

extract_negative_modes only took an argument starting with '-' as a mode when its second character was a permission letter or a digit. Modes such as "-=r", "-+x" and "-,u+x" went on to clap, which has no such option and rejected them. Also accept '=', '+' and ',' there; no option starts with those.

Closes #15665
---
 src/uu/chmod/src/chmod.rs   |  4 +++-
 tests/by-util/test_chmod.rs | 25 +++++++++++++++++++++++++
 2 files changed, 28 insertions(+), 1 deletion(-)

diff --git a/src/uu/chmod/src/chmod.rs b/src/uu/chmod/src/chmod.rs
index 80d96e855c7..55ee2d92520 100644
--- a/src/uu/chmod/src/chmod.rs
+++ b/src/uu/chmod/src/chmod.rs
@@ -79,11 +79,13 @@ fn extract_negative_modes(args: impl uucore::Args) -> (Option<String>, Vec<OsStr
         let Some(arg) = arg.to_str() else {
             return false;
         };
+        // A mode can also be "-=r", "-+x" or "-,u+x". No option starts with '=', '+' or ',',
+        // and a second '-' (a long option) is deliberately not listed.
         arg.len() >= 2
             && arg.starts_with('-')
             && matches!(
                 arg.chars().nth(1).unwrap(),
-                'r' | 'w' | 'x' | 'X' | 's' | 't' | 'u' | 'g' | 'o' | '0'..='7'
+                'r' | 'w' | 'x' | 'X' | 's' | 't' | 'u' | 'g' | 'o' | '=' | '+' | ',' | '0'..='7'
             )
     };
 
diff --git a/tests/by-util/test_chmod.rs b/tests/by-util/test_chmod.rs
index 01052cf6c2c..3d901f6b89f 100644
--- a/tests/by-util/test_chmod.rs
+++ b/tests/by-util/test_chmod.rs
@@ -364,6 +364,31 @@ fn test_chmod_many_options() {
     run_tests(tests);
 }
 
+#[test]
+fn test_chmod_option_like_mode_starting_with_operator() {
+    let tests = vec![
+        TestCase {
+            args: vec!["-=r", TEST_FILE],
+            before: 0o100_644,
+            after: 0o100_444,
+            umask: Some(0o022),
+        },
+        TestCase {
+            args: vec!["-+x", TEST_FILE],
+            before: 0o100_644,
+            after: 0o100_755,
+            umask: Some(0o022),
+        },
+        TestCase {
+            args: vec!["-,u+x", TEST_FILE],
+            before: 0o100_644,
+            after: 0o100_744,
+            umask: Some(0o022),
+        },
+    ];
+    run_tests(tests);
+}
+
 #[test]
 #[allow(clippy::unreadable_literal)]
 fn test_chmod_reference_file() {