shutdown: Port to LibMain

Author: https://github.com/alexmajor
Commit: 55496ab7fb
Pull-request: https://github.com/SerenityOS/serenity/pull/12034
Reviewed-by: https://github.com/alimpfard
Reviewed-by: https://github.com/bgianfo
Reviewed-by: https://github.com/kennethmyhra
Reviewed-by: https://github.com/mjz19910

Userland/Utilities/shutdown.cpp

@@ -1,25 +1,24 @@
 /*
  * Copyright (c) 2018-2020, Andreas Kling <kling@serenityos.org>
  * Copyright (c) 2021, Liav A. <liavalb@hotmail.co.il>
+ * Copyright (c) 2022, Alex Major
  *
  * SPDX-License-Identifier: BSD-2-Clause
  */
 
+#include <LibCore/Stream.h>
+#include <LibMain/Main.h>
 #include <fcntl.h>
 #include <stdio.h>
 #include <unistd.h>
 
-int main(int, char**)
+ErrorOr<int> serenity_main(Main::Arguments)
 {
-    int power_state_switch_node = open("/sys/firmware/power_state", O_WRONLY);
-    if (power_state_switch_node < 0) {
-        perror("open");
-        return 1;
-    }
-    const char* value = "2";
-    if (write(power_state_switch_node, value, 1) < 0) {
-        perror("write");
-        return 1;
-    }
+    auto file = TRY(Core::Stream::File::open("/sys/firmware/power_state", Core::Stream::OpenMode::Write));
+
+    const String file_contents = "2";
+    TRY(file->write(file_contents.bytes()));
+    file->close();
+
     return 0;
 }