From 22c5cf3e4b614f8f033224bb87a18cdaf86308b7 Mon Sep 17 00:00:00 2001
From: vatsanbalaji-ossagent
 <325768530+vatsanbalaji-ossagent@users.noreply.github.com>
Date: Mon, 12 Oct 2026 12:14:04 -0400
Subject: [PATCH 1/2] chgrp: reject the :gid format for the group operand

GNU chgrp only accepts a group name or numeric ID as the group operand
and rejects ":1000" as an invalid group. Only --from accepts the :gid
format, so parse the operand separately and add a regression test.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 src/uu/chgrp/src/chgrp.rs   | 24 +++++++++++++++---------
 tests/by-util/test_chgrp.rs | 12 ++++++++++++
 2 files changed, 27 insertions(+), 9 deletions(-)

diff --git a/src/uu/chgrp/src/chgrp.rs b/src/uu/chgrp/src/chgrp.rs
index 065b52ccae6..5b1d4263f5a 100644
--- a/src/uu/chgrp/src/chgrp.rs
+++ b/src/uu/chgrp/src/chgrp.rs
@@ -27,6 +27,18 @@ enum ChgrpError {
 
 impl UError for ChgrpError {}
 
+fn parse_group(group: &str) -> Result<u32, String> {
+    // Try as group name first
+    match entries::grp2gid(group) {
+        Ok(g) => Ok(g),
+        // If group name lookup fails, try parsing as raw number
+        Err(_) => group
+            .parse::<u32>()
+            .map_err(|_| translate!("chgrp-error-invalid-group", "group" => group)),
+    }
+}
+
+/// Parse the `--from` value, which also accepts the `:gid` format.
 fn parse_gid_from_str(group: &str) -> Result<u32, String> {
     if let Some(gid_str) = group.strip_prefix(':') {
         // Handle :gid format
@@ -34,14 +46,7 @@ fn parse_gid_from_str(group: &str) -> Result<u32, String> {
             .parse::<u32>()
             .map_err(|_| translate!("chgrp-error-invalid-group-id", "gid_str" => gid_str))
     } else {
-        // Try as group name first
-        match entries::grp2gid(group) {
-            Ok(g) => Ok(g),
-            // If group name lookup fails, try parsing as raw number
-            Err(_) => group
-                .parse::<u32>()
-                .map_err(|_| translate!("chgrp-error-invalid-group", "group" => group)),
-        }
+        parse_group(group)
     }
 }
 
@@ -67,7 +72,8 @@ fn get_dest_gid(matches: &ArgMatches) -> UResult<(Option<u32>, String)> {
         if group.is_empty() {
             None
         } else {
-            match parse_gid_from_str(group) {
+            // Unlike --from, GNU does not accept the `:gid` format here.
+            match parse_group(group) {
                 Ok(g) => Some(g),
                 Err(e) => return Err(USimpleError::new(1, e)),
             }
diff --git a/tests/by-util/test_chgrp.rs b/tests/by-util/test_chgrp.rs
index 3f29e130a69..9dd6c7c5ce7 100644
--- a/tests/by-util/test_chgrp.rs
+++ b/tests/by-util/test_chgrp.rs
@@ -62,6 +62,18 @@ fn test_invalid_group() {
         .stderr_is("chgrp: invalid group: '__nosuchgroup__'\n");
 }
 
+#[test]
+fn test_invalid_group_with_colon_prefix() {
+    // The `:gid` format is only accepted by --from, not for the group operand
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.touch("file");
+    let gid = getegid().as_raw();
+    ucmd.arg(format!(":{gid}"))
+        .arg("file")
+        .fails_with_code(1)
+        .stderr_is(format!("chgrp: invalid group: ':{gid}'\n"));
+}
+
 #[test]
 fn test_error_1() {
     if !getegid().is_root() {

From 2a0c5fc3fc50a7f0b6a2da9d616f187783b7093b Mon Sep 17 00:00:00 2001
From: vatsanbalaji-ossagent
 <325768530+vatsanbalaji-ossagent@users.noreply.github.com>
Date: Tue, 13 Oct 2026 11:57:26 -0400
Subject: [PATCH 2/2] chgrp: use a numeric gid for the target group in test

test_numeric_group_formats still passed ":gid" as the group operand,
which is now rejected. Use the plain numeric gid instead.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>
---
 tests/by-util/test_chgrp.rs | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/tests/by-util/test_chgrp.rs b/tests/by-util/test_chgrp.rs
index 9dd6c7c5ce7..b128e64d0da 100644
--- a/tests/by-util/test_chgrp.rs
+++ b/tests/by-util/test_chgrp.rs
@@ -616,11 +616,11 @@ fn test_numeric_group_formats() {
     let new_gid = at.plus("test_file").metadata().unwrap().gid();
     assert_eq!(new_gid, second_group.as_raw());
 
-    // Test :gid format in target group
+    // Test numeric gid in target group (the :gid format is only valid for --from)
     scene
         .ucmd()
         .arg(format!("--from={}", second_group.as_raw()))
-        .arg(format!(":{}", first_group.as_raw()))
+        .arg(first_group.as_raw().to_string())
         .arg("test_file")
         .succeeds()
         .no_stderr();