timezone: Add a command line utility to set the system time zone

Meta/build-root-filesystem.sh

@@ -101,6 +101,10 @@ if [ -f mnt/bin/utmpupdate ]; then
     chown 0:$utmp_gid mnt/bin/utmpupdate
     chmod 2755 mnt/bin/utmpupdate
 fi
+if [ -f mnt/bin/timezone ]; then
+    chown 0:$phys_gid mnt/bin/timezone
+    chmod 4750 mnt/bin/timezone
+fi
 if [ -f mnt/usr/Tests/Kernel/TestMemoryDeviceMmap ]; then
     chown 0:0 mnt/usr/Tests/Kernel/TestMemoryDeviceMmap
     chmod 4755 mnt/usr/Tests/Kernel/TestMemoryDeviceMmap

Userland/Utilities/CMakeLists.txt

@@ -156,6 +156,7 @@ target_link_libraries(telws LibProtocol LibLine)
 target_link_libraries(test-fuzz LibCore LibGemini LibGfx LibHTTP LibIPC LibJS LibMarkdown LibShell)
 target_link_libraries(test-imap LibIMAP LibMain)
 target_link_libraries(test-pthread LibThreading)
+target_link_libraries(timezone LibMain)
 target_link_libraries(top LibMain)
 target_link_libraries(touch LibMain)
 target_link_libraries(truncate LibMain)

Userland/Utilities/timezone.cpp

@@ -0,0 +1,33 @@
+/*
+ * Copyright (c) 2022, Tim Flynn <trflynn89@pm.me>
+ *
+ * SPDX-License-Identifier: BSD-2-Clause
+ */
+
+#include <AK/StringView.h>
+#include <AK/Try.h>
+#include <LibCore/ArgsParser.h>
+#include <LibCore/System.h>
+#include <LibMain/Main.h>
+#include <LibTimeZone/TimeZone.h>
+
+ErrorOr<int> serenity_main(Main::Arguments arguments)
+{
+    TRY(Core::System::pledge("stdio rpath wpath cpath"));
+    TRY(Core::System::unveil("/etc/timezone", "rwc"));
+    TRY(Core::System::unveil(nullptr, nullptr));
+
+    StringView time_zone;
+
+    Core::ArgsParser args_parser;
+    args_parser.add_positional_argument(time_zone, "The time zone to set", "time-zone", Core::ArgsParser::Required::No);
+    args_parser.parse(arguments);
+
+    if (time_zone.is_empty()) {
+        outln("{}", TimeZone::current_time_zone());
+        return 0;
+    }
+
+    TRY(TimeZone::change_time_zone(time_zone));
+    return 0;
+}