chgrp: handle empty group

src/uu/chgrp/src/chgrp.rs

@@ -161,12 +161,9 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         Verbosity::Normal
     };
 
-    let dest_gid: u32;
-    if let Some(file) = matches.value_of(options::REFERENCE) {
+    let dest_gid = if let Some(file) = matches.value_of(options::REFERENCE) {
         match fs::metadata(&file) {
-            Ok(meta) => {
-                dest_gid = meta.gid();
-            }
+            Ok(meta) => Some(meta.gid()),
             Err(e) => {
                 show_error!("failed to get attributes of '{}': {}", file, e);
                 return 1;
@@ -174,16 +171,18 @@ pub fn uumain(args: impl uucore::Args) -> i32 {
         }
     } else {
         let group = matches.value_of(options::ARG_GROUP).unwrap_or_default();
-        match entries::grp2gid(group) {
-            Ok(g) => {
-                dest_gid = g;
-            }
-            _ => {
-                show_error!("invalid group: {}", group);
-                return 1;
+        if group.is_empty() {
+            None
+        } else {
+            match entries::grp2gid(group) {
+                Ok(g) => Some(g),
+                _ => {
+                    show_error!("invalid group: {}", group);
+                    return 1;
+                }
             }
         }
-    }
+    };
 
     let executor = Chgrper {
         bit_flag,
@@ -278,7 +277,7 @@ pub fn uu_app() -> App<'static, 'static> {
 }
 
 struct Chgrper {
-    dest_gid: gid_t,
+    dest_gid: Option<gid_t>,
     bit_flag: u8,
     verbosity: Verbosity,
     files: Vec<String>,

src/uu/install/src/install.rs

@@ -660,7 +660,7 @@ fn copy(from: &Path, to: &Path, b: &Behavior) -> UResult<()> {
             Ok(g) => g,
             _ => return Err(InstallError::NoSuchGroup(b.group.clone()).into()),
         };
-        match wrap_chgrp(to, &meta, group_id, false, Verbosity::Normal) {
+        match wrap_chgrp(to, &meta, Some(group_id), false, Verbosity::Normal) {
             Ok(n) => {
                 if !n.is_empty() {
                     show_error!("{}", n);

src/uucore/src/lib/features/perms.rs

@@ -49,13 +49,14 @@ fn chgrp<P: AsRef<Path>>(path: P, gid: gid_t, follow: bool) -> IOResult<()> {
 pub fn wrap_chgrp<P: AsRef<Path>>(
     path: P,
     meta: &Metadata,
-    dest_gid: gid_t,
+    dest_gid: Option<gid_t>,
     follow: bool,
     verbosity: Verbosity,
 ) -> Result<String, String> {
     use self::Verbosity::*;
     let path = path.as_ref();
     let mut out: String = String::new();
+    let dest_gid = dest_gid.unwrap_or_else(|| meta.gid());
 
     if let Err(e) = chgrp(path, dest_gid, follow) {
         match verbosity {

tests/by-util/test_chgrp.rs

@@ -228,3 +228,10 @@ fn test_big_h() {
         );
     }
 }
+
+#[test]
+fn test_no_change() {
+    let (at, mut ucmd) = at_and_ucmd!();
+    at.touch("file");
+    ucmd.arg("").arg(at.plus("file")).succeeds();
+}