source: bootcd/isolinux/syslinux-6.03/gnu-efi/gnu-efi-3.0/apps/t7.c

#include <efi.h>
#include <efilib.h>

EFI_STATUS
efi_main (EFI_HANDLE image, EFI_SYSTEM_TABLE *systab)
{
        EFI_INPUT_KEY efi_input_key;
        EFI_STATUS efi_status;

        InitializeLib(image, systab);

        Print(L"HelloLib application started\n");

        Print(L"\n\n\nHit any key to exit this image\n");
        WaitForSingleEvent(ST->ConIn->WaitForKey, 0);

        uefi_call_wrapper(ST->ConOut->OutputString, 2, ST->ConOut, L"\n\n");

        efi_status = uefi_call_wrapper(ST->ConIn->ReadKeyStroke, 2, ST->ConIn, &efi_input_key);

        Print(L"ScanCode: %xh  UnicodeChar: %xh\n",
                efi_input_key.ScanCode, efi_input_key.UnicodeChar);

        return EFI_SUCCESS;
}