chmod: Implement the --recursive flag

Userland/Utilities/chmod.cpp

@@ -8,6 +8,7 @@
 
 #include <AK/Vector.h>
 #include <LibCore/ArgsParser.h>
+#include <LibCore/DirIterator.h>
 #include <LibCore/FilePermissionsMask.h>
 #include <LibCore/System.h>
 #include <LibMain/Main.h>
@@ -18,17 +19,43 @@ ErrorOr<int> serenity_main(Main::Arguments arguments)
 
     StringView mode;
     Vector<StringView> paths;
+    bool recursive = false;
 
     Core::ArgsParser args_parser;
+    args_parser.add_option(recursive, "Change file modes recursively", "recursive", 'R');
     args_parser.add_positional_argument(mode, "File mode in octal or symbolic notation", "mode");
     args_parser.add_positional_argument(paths, "Paths to file", "paths");
     args_parser.parse(arguments);
 
     auto mask = TRY(Core::FilePermissionsMask::parse(mode));
 
+    Function<ErrorOr<void>(StringView const&)> update_path_permissions = [&](StringView const& path) -> ErrorOr<void> {
+        auto stat = TRY(Core::System::lstat(path));
+
+        if (S_ISLNK(stat.st_mode)) {
+            // Symlinks don't get processed unless they are explicitly listed on the command line.
+            if (!paths.contains_slow(path))
+                return {};
+
+            // The chmod syscall changes the file that a link points to, so we will have to get
+            // the correct mode to base our modifications on.
+            stat = TRY(Core::System::stat(path));
+        }
+
+        TRY(Core::System::chmod(path, mask.apply(stat.st_mode)));
+
+        if (recursive && S_ISDIR(stat.st_mode)) {
+            Core::DirIterator it(path, Core::DirIterator::Flags::SkipParentAndBaseDir);
+
+            while (it.has_next())
+                TRY(update_path_permissions(it.next_full_path()));
+        }
+
+        return {};
+    };
+
     for (auto const& path : paths) {
-        auto current_access = TRY(Core::System::stat(path));
+        TRY(update_path_permissions(path));
-        TRY(Core::System::chmod(path, mask.apply(current_access.st_mode)));
     }
 
     return 0;