Utilities: Add the listdir utility

This utility uses the Core::DirIterator facility which in turn uses the
get_dir_entries syscall. Therefore, this utility lets us to view the
actual values for inode numbers, and entry type value for directory
entries.

Author: supercomputer7

Base/usr/share/man/man1/listdir.md

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+## Name
+
+lsdir - list directory entries
+
+## Synopsis
+
+```**sh
+# lsdir [options...] [path...]
+```
+
+## Description
+
+This utility will list all directory entries of a given path (or list of paths)
+and print their inode number and file type (in either POSIX DT_* format or human readable).
+
+The utility uses `LibCore` `DirIterator` object and restrict its functionality
+to the `get_dir_entries` syscall only, to get the raw values of each directory
+entry.
+
+## Options
+
+* `-P`, `--posix-names`: Show POSIX names for file types
+* `-t`, `--total-entries-count`: Print count of listed entries when traversing a directory
+
+## Arguments
+
+* `path`: Directory to list
+
+## Examples
+
+```sh
+# List directory entries of working directory
+$ lsdir
+# List directory entries of /proc directory 
+$ lsdir /proc
+# List directory entries of /proc directory with POSIX names for file types
+$ lsdir -P /proc
+# List directory entries of /proc directory and print in the end the count of traversed entries
+$ lsdir -t /proc
+```
+
+## See also
+* [`ls`(1)](help://man/1/ls)

Userland/Utilities/listdir.cpp

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+/*
+ * Copyright (c) 2024, Liav A. <[email protected]>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/Function.h>
+#include <AK/StringView.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/DirIterator.h>
+#include <LibCore/DirectoryEntry.h>
+#include <LibCore/System.h>
+#include <LibMain/Main.h>
+
+static bool flag_show_unix_posix_file_type = false;
+static bool flag_show_total_count = false;
+
+ErrorOr<int> serenity_main(Main::Arguments arguments)
+{
+    TRY(Core::System::pledge("stdio rpath"));
+
+    Vector<StringView> paths;
+
+    Core::ArgsParser args_parser;
+    args_parser.set_general_help("List Dirent entries in a directory.");
+    args_parser.add_option(flag_show_unix_posix_file_type, "Show POSIX names for file types", "posix-names", 'P');
+    args_parser.add_option(flag_show_total_count, "Show total count for each directory being iterated", "total-entries-count", 't');
+    args_parser.add_positional_argument(paths, "Directory to list", "path", Core::ArgsParser::Required::No);
+    args_parser.parse(arguments);
+
+    if (paths.is_empty())
+        paths.append("."sv);
+
+    for (auto& path : paths) {
+        Core::DirIterator di(path, Core::DirIterator::NoStat);
+        if (di.has_error()) {
+            auto error = di.error();
+            warnln("Failed to open {} - {}", path, error);
+            return error;
+        }
+
+        outln("Traversing {}", path);
+        size_t count = 0;
+
+        Function<StringView(Core::DirectoryEntry::Type)> name_from_directory_entry_type;
+        if (flag_show_unix_posix_file_type)
+            name_from_directory_entry_type = Core::DirectoryEntry::posix_name_from_directory_entry_type;
+        else
+            name_from_directory_entry_type = Core::DirectoryEntry::representative_name_from_directory_entry_type;
+
+        while (di.has_next()) {
+            auto dir_entry = di.next();
+            if (dir_entry.has_value()) {
+                outln("    {} (Type: {}, Inode number: {})",
+                    dir_entry.value().name,
+                    name_from_directory_entry_type(dir_entry.value().type),
+                    dir_entry.value().inode_number);
+                count++;
+            }
+        }
+        if (flag_show_total_count)
+            outln("Directory {} has {} which has being listed during the program runtime", path, count);
+    }
+
+    return 0;
+}