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-In previous lesson we've used `EFI_SHELL_PARAMETERS_PROTOCOL` to get command line parameters to our app.
-It is a valid method but there is a simpler way to do it for the shell apps.
-
-To ease things we can use the entry point in this format:
-https://github.com/tianocore/edk2/blob/master/ShellPkg/Include/Library/ShellCEntryLib.h
-```
-INTN
-EFIAPI
-ShellAppMain (
- IN UINTN Argc,
- IN CHAR16 **Argv
- );
-```
-This way `Argc`/`Argv` are passed directly to the app entry point like it is usually happening in C programming.
-
-Let's create a `SimpleShellApp` based on our `HelloWorld` app.
-
-With the necessary modifications the INF file would look like this:
-```
-[Defines]
- INF_VERSION = 1.25
- BASE_NAME = SimpleShellApp
- FILE_GUID = 2afd1202-545e-4f8d-b8fb-bc179e84ddc8
- MODULE_TYPE = UEFI_APPLICATION
- VERSION_STRING = 1.0
- ENTRY_POINT = ShellCEntryLib
-
-[Sources]
- SimpleShellApp.c
-
-[Packages]
- MdePkg/MdePkg.dec
-
-[LibraryClasses]
- UefiApplicationEntryPoint
- UefiLib
- ShellCEntryLib
-```
-Main changes:
-- `ENTRY_POINT = ShellCEntryLib` is added to the `[Defines]` section
-- `ShellCEntryLib` is added to the `[LibraryClasses]` section
-
-In the end it works this way. Shell C library is the main UEFI app with the standard entry point:
-```
-EFI_STATUS
-EFIAPI
-UefiMain (
- IN EFI_HANDLE ImageHandle,
- IN EFI_SYSTEM_TABLE *SystemTable
- )
-```
-It parses incoming parameters with the `EFI_SHELL_PARAMETERS_PROTOCOL` like we did it and then calls our app entry point passing all of the parsed parameteres with the call:
-```
-INTN
-EFIAPI
-ShellAppMain (
- IN UINTN Argc,
- IN CHAR16 **Argv
- );
-```
-You can look at the source code of `ShellAppMain` at the https://github.com/tianocore/edk2/blob/master/ShellPkg/Library/UefiShellCEntryLib/UefiShellCEntryLib.c
-
-If you look at the source you could see that istead of a `HandleProtocol` API that we've used:
-```
-Status = gBS->HandleProtocol(
- ImageHandle,
- &gEfiShellParametersProtocolGuid,
- (VOID **) &ShellParameters
-);
-```
-it uses `OpenProtocol` API: (I've modified a code a little bit to make it comparable to our version)
-```
-Status = gBS->OpenProtocol(
- ImageHandle,
- &gEfiShellParametersProtocolGuid,
- (VOID **)&ShellParameters,
- ImageHandle,
- NULL,
- EFI_OPEN_PROTOCOL_GET_PROTOCOL
-);
-```
-According to the UEFI spec `HandleProtocol` API is outdated and `OpenProtocol` should be used instead.
-`OpenProtocol` API is a more general call that can cover more cases. It all would matter when you start develop UEFI drivers. You can read UEFI spec for more information. Right now just accept a fact that for the UEFI app these two calls are the same.
-
-Let's go back to our code. To find the necessary `ShellCEntryLib` library class search as usual:
-```
-$ grep ShellCEntryLib -r ./ --include=*.inf | grep LIBRARY_CLASS
-./ShellPkg/Library/UefiShellCEntryLib/UefiShellCEntryLib.inf: LIBRARY_CLASS = ShellCEntryLib|UEFI_APPLICATION UEFI_DRIVER
-```
-
-Add this library class to our `UefiLessonsPkg/UefiLessonsPkg.dsc`:
-```
-ShellCEntryLib|ShellPkg/Library/UefiShellCEntryLib/UefiShellCEntryLib.inf
-```
-Don't forget also to add our new app under the `[Components]` section:
-```
-UefiLessonsPkg/SimpleShellApp/SimpleShellApp.inf
-```
-
-
-Now let's look at the `*.c` file.
-
-We can't use our first print method as `SystemTable` now is unavailable, but we can simply use `SystemTable` with the help of `gST` pointer:
-```
-#include <Library/UefiBootServicesTableLib.h>
-#include <Library/UefiLib.h>
-
-INTN EFIAPI ShellAppMain(IN UINTN Argc, IN CHAR16 **Argv)
-{
- Print(L"Argc=%d\n", Argc);
-// SystemTable->ConOut->OutputString(SystemTable->ConOut, L"Hello World!\n");
- gST->ConOut->OutputString(gST->ConOut, L"Hello again!\n");
- Print(L"Bye!\n");
- return 0;
-}
-```
-
-Let's add some parameters handling code:
-```
-for (UINTN i=Argc; i>0; i--) {
- Print(L"Arg[%d]=%s\n", Argc-i, Argv[Argc-i]);
-}
-```
-
-If we test our app under OVMF we would get:
-```
-FS0:\> SimpleShellApp.efi kkk ggg
-Hello again!
-Bye!
-Arg[0]=FS0:\SimpleShellApp.efi
-Arg[1]=kkk
-Arg[2]=ggg
-FS0:\> SimpleShellApp.efi
-Hello again!
-Bye!
-Arg[0]=FS0:\SimpleShellApp.efi
-```