#ifndef _NTDBG_H

NTSYSAPI
ULONG
NTAPI
DbgPrompt(
    _In_ PCCH Prompt,
    _Out_writes_bytes_(Length) PCH Response,
    _In_ ULONG Length
    );

#endif
View code on GitHub

// ntddk.h

NTSYSAPI ULONG DbgPrompt(
  [in]  PCCH  Prompt,
  [out] PCH   Response,
        ULONG Length
);
View the official Windows Driver Kit DDI reference

NtDoc

This function is documented in Windows Driver Kit.

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Windows Driver Kit DDI reference (nf-ntddk-dbgprompt)

Description

The DbgPrompt routine displays a caller-specified user prompt string on the kernel debugger's display device and obtains a user response string.

Parameters

`Prompt` [in]

A pointer to a NULL-terminated constant character string that the debugger will display as a user prompt. The maximum size of this string is 512 characters.

`Response` [out]

A pointer to a character array buffer that receives the user's response, including a terminating newline character. The maximum size of this buffer is 512 characters.

`Length`

The size, in characters, of the buffer that receives the user's response. This size is the maximum number of characters that the routine will return.

Return value

DbgPrompt returns the number of characters that the Response buffer received, including the terminating newline character. DbgPrompt returns zero if it receives no characters.

Remarks

The DbgPrompt routine displays the specified prompt string on the kernel debugger's display device and then reads a line of user input text.

After DbgPrompt returns, the Response buffer contains the user's response, including the terminating newline character. The user response string is not NULL-terminated.

The following code example asks if the user wants to continue and accepts the letter "y" for yes and the letter "n" for no.

CHAR Response[2];
BOOLEAN Continue = FALSE;
ULONG CharCount;
for (;;) {
 CharCount = DbgPrompt(
  "Do you want to continue? (Type y or n, then type Enter.) ",
  Response,
  sizeof(Response)
  );

 if (CharCount == 2) {
 if (Response[0] == 'y') {
  Continue = TRUE;
  break;
  } else if (Response[0] == 'n') {
  break;
     }
    }

    //
    // Incorrect response. Display the prompt again.
    //
}

View the official Windows Driver Kit DDI reference