| Platform SDK: Files and I/O |
The following sample demonstrates how to add or remove persistent drive letter assignments in Windows 2000. These drive letter assignments persist through machine reboots.
This sample uses the following functions: DefineDosDevice, DeleteVolumeMountPoint, GetVolumeNameForVolumeMountPoint, and SetVolumeMountPoint.
/*
DLEDIT -- Drive Letter Assignment Editor
Platforms:
This program requires Windows 2000.
Command-line syntax:
DLEDIT <drive letter> <NT device name> -- Adds a drive letter
DLEDIT -r <drive letter> -- Removes a drive letter
Command-line examples:
If E: refers to the CD-ROM drive, use the following commands to
make F: point to the CD-ROM drive instead.
DLEDIT -r E:\
DLEDIT F:\ \Device\CdRom0
*****************************************************************
WARNING WARNING WARNING WARNING WARNING WARNING WARNING WARNING
This program will change drive letter assignments, and the
changes persist through reboots. Do not remove drive letters
of your hard disks if you do not have this program on floppy
disk or you might not be able to access your hard disks again!
*****************************************************************
*/
#define _WIN32_WINNT 0x0500
#include <windows.h>
#include <stdio.h>
#if defined (DEBUG)
static void DebugPrint (LPCSTR pszMsg, DWORD dwErr);
#define DEBUG_PRINT(pszMsg, dwErr) DebugPrint(pszMsg, dwErr)
#else
#define DEBUG_PRINT(pszMsg, dwErr) NULL
#endif
#pragma warning (disable : 4800)
void PrintHelp (LPCSTR pszAppName);
/*--------------------------------------------------------------------
The main function is the main routine. It parses the command-line
arguments and either removes or adds a drive letter.
Parameters
argc
Count of the command-line arguments
argv
Array of pointers to the individual command-line arguments
--------------------------------------------------------------------*/
void main (int argc, char **argv)
{
char * pszDriveLetter,
* pszNTDevice,
* pszOptions;
char szUniqueVolumeName[MAX_PATH];
char szDriveLetterAndSlash[4];
char szDriveLetter[3];
bool fRemoveDriveLetter;
bool fResult;
if (argc != 3)
{
PrintHelp(argv[0]);
return;
}
// Use the command line to see if user wants to add or remove the
// drive letter. Do this by looking for the -r option.
fRemoveDriveLetter = !lstrcmpi (argv[1], "-r");
if (fRemoveDriveLetter)
{
// User wants to remove the drive letter. Command line should
// be: dl -r <drive letter>
pszOptions = argv[1];
pszDriveLetter = argv[2];
pszNTDevice = NULL;
}
else
{
// User wants to add a drive letter. Command line should be:
// dl <drive letter> <NT device name>
pszOptions = NULL;
pszDriveLetter = argv[1];
pszNTDevice = argv[2];
}
// GetVolumeNameForVolumeMountPoint, SetVolumeMountPoint, and
// DeleteVolumeMountPoint require drive letters to have a trailing
// backslash. However, DefineDosDevice requires that the trailing
// backslash be absent. So, we'll use:
//
// szDriveLetterAndSlash for the mount point APIs
// szDriveLetter for DefineDosDevice
//
// This way, we can accept command lines that use a: or a:\
// for drive letters without writing back to the original command-
// line argument.
szDriveLetter[0] = pszDriveLetter[0];
szDriveLetter[1] = ':';
szDriveLetter[2] = '\0';
szDriveLetterAndSlash[0] = pszDriveLetter[0];
szDriveLetterAndSlash[1] = ':';
szDriveLetterAndSlash[2] = '\\';
szDriveLetterAndSlash[3] = '\0';
// Now add or remove the drive letter.
if (fRemoveDriveLetter)
{
fResult = DeleteVolumeMountPoint (szDriveLetterAndSlash);
if (!fResult)
printf("error %lu: couldn't remove %s\n",
GetLastError(), szDriveLetterAndSlash);
}
else
{
// To add a drive letter that persists through reboots, use
// SetVolumeMountPoint. This requires the unique volume name of
// the device to which the new drive letter will refer. To get
// the unique volume name, use GetVolumeNameForVolumeMountPoint;
// it requires the drive letter to already exist. So, we first
// define the drive letter as a symbolic link to the device
// name. After we have the unique volume name the new drive
// letter will point to, we must delete the symbolic link
// because the mount manager allows only one reference to a
// device at a time (the new one to be added).
fResult = DefineDosDevice (DDD_RAW_TARGET_PATH, szDriveLetter,
pszNTDevice);
if (fResult)
{
// If GetVolumeNameForVolumeMountPoint fails, then
// SetVolumeMountPoint will also fail. However, we must call
// DefineDosDevice to remove the temporary symbolic link.
// Therefore, set szUniqueVolume to a known empty string.
if (!GetVolumeNameForVolumeMountPoint (szDriveLetterAndSlash,
szUniqueVolumeName,
MAX_PATH))
{
DEBUG_PRINT("GetVolumeNameForVolumeMountPoint failed",
GetLastError());
szUniqueVolumeName[0] = '\0';
}
fResult = DefineDosDevice (
DDD_RAW_TARGET_PATH|DDD_REMOVE_DEFINITION|
DDD_EXACT_MATCH_ON_REMOVE, szDriveLetter,
pszNTDevice);
if (!fResult)
DEBUG_PRINT("DefineDosDevice failed", GetLastError());
fResult = SetVolumeMountPoint (szDriveLetterAndSlash,
szUniqueVolumeName);
if (!fResult)
printf ("error %lu: could not add %s\n", GetLastError(),
szDriveLetterAndSlash);
}
}
}
/*-------------------------------------------------------------------
The PrintHelp function prints the command-line usage help.
Parameters
pszAppName
The name of the executable. Used in displaying the help.
-------------------------------------------------------------------*/
void PrintHelp (LPCSTR pszAppName)
{
printf("Adds/removes a drive letter assignment for a device.\n\n");
printf("Usage: %s <Drive> <Device name> add a drive letter\n", pszAppName);
printf(" %s -r <Drive> remove a drive letter\n\n", pszAppName);
printf("Example: %s e:\\ \\Device\\CdRom0\n", pszAppName);
printf(" %s -r e:\\\n", pszAppName);
}
#if defined (DEBUG)
/*--------------------------------------------------------------------
The DebugPrint function prints a string to STDOUT.
Parameters
pszMsg
The string to be printed to STDOUT.
dwErr
The error code; usually obtained from GetLastError. If dwErr is
zero, no error code is added to the error string. If dwErr is
nonzero, the error code will be printed in the error string.
--------------------------------------------------------------------*/
void DebugPrint (LPCSTR pszMsg, DWORD dwErr)
{
if (dwErr)
printf("%s: %lu\n", pszMsg, dwErr);
else
printf("%s\n", pszMsg);
}
#endif
When building this sample program, use the following makefile.
APPVER = 5.0
TARGETOS = WINNT
!include <win32.mak>
PROJ = DLEDIT
all: $(PROJ).exe
PROJ_OBJS = dledit.obj
.cpp.obj:
$(cc) $(cdebug) $(cflags) $(cvars) $<
$(PROJ).exe: $(PROJ_OBJS)
$(link) $(ldebug) $(conlflags)\
$(PROJ_OBJS) \
-out:$(PROJ).exe \
$(conlibs)
clean:
del *.bak
del *.opt
del *.pdb
del *.obj
cleaner: clean
del *.exe