psubst: attempt to make virtual drives persistently

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siberia-man
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psubst: attempt to make virtual drives persistently

#1 Post by siberia-man » 05 Mar 2020 04:36

DESCRIPTION

Times ago I invented the tool PSUBST being the extended version for the standard SUBST. Both tools allow to associate some paths with virtual drives. So executing the following command we have ability to achieve the particular path in two ways by the path itself and/or by the drive:

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subst Z: "C:\Documents and Settings\All Users\Shared Documents"
Unfortunately these virtual drives are not persistent between the system rebooting. Another lack is that if we need SUBSTed drive on the earliest stage of booting (for example, for services or something else) we can establish SUBSTed drives. Good news that Win (since WinXP till the present) has ability to establish virtual drives. It requires some work with the Registry within the HKLM hive. So the main goal of my tool is to combine the existing functionality of the standard tool SUBST with the Registry handling. Possibility to make virtual drives persistent is turned with the special option /P standing for persistency. For long time it was working fine but sometimes it required higher permissions to update the HKLM hive. Running the tool with elevated privileges solved the issue. Couple days ago I found how to simplify usage of PSUBST -- no needs to run it especially with elevated privileges. It tries to manage them by its own.

STANDARD USAGE EXAMPLES

There is brief usage of the tool.

In fact, the tool mimics to SUBST. So there are no needs to duplicate its help page.

Display SUBSTed drives (in this case it acts absolutely as the original tool SUBST):

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psubst
EXTENDED USAGE EXAMPLES

Display persistently SUBSTed drives:

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psubst /p
Create the persistently SUBSTed drive with the current user privileges:

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psubst Z: "C:\Documents and Settings\All Users\Shared Documents" /p
Create the persistently SUBSTed drive with the elevated privileges:

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psubst Z: "C:\Documents and Settings\All Users\Shared Documents" /pf
Delete the persistently SUBSTed drive with the current user privileges:

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psubst Z: /d /p
Delete the persistently SUBSTed drive with the elevated privileges:

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psubst Z: /d /pf
Privileges elevation is based on the idea provided by Eureka! in his post SUDO for CMD.

Restore the virtual drive, reading it from the persistency storage (the Registry in fact):

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psubst Z: /p
The last example can be useful when:
-- you create a new SUBSTed drive (persistent one and SUBST it for the current session)
-- deleted drive and want to restore it.

Indeed, the following example (with /P or /PF):

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psubst Z: "C:\Documents and Settings\All Users\Shared Documents" /p
psubst Z: /p
is shorter and better than

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psubst Z: "C:\Documents and Settings\All Users\Shared Documents" /p
psubst Z: "C:\Documents and Settings\All Users\Shared Documents"
DOWNLOADS

The latest version of the tool can be found at https://github.com/ildar-shaimordanov/psubst/releases

SOURCE

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::PSUBST v3.0.1-0-gbbb9804
::
::Associates a path with a drive letter.
::Manages persistently substituted (virtual) drives.
::
::PSUBST [drive1: [drive2:]path] [/P | /PF]
::PSUBST drive1: /D [/P | /PF]
::PSUBST drive1: /P
::
::  drive1:        Specifies a virtual drive to which you want to assign a path.
::  [drive2:]path  Specifies a physical drive and path you want to assign to
::                 a virtual drive.
::  /D             Deletes a substituted (virtual) drive.
::  /P             Add, delete or display persistent drives.
::  /PF            Add or delete persistent drives with elevated privileges.
::
::Type PSUBST with no parameters to display a list of current virtual drives.
::Type PSUBST /P to display a list of persistent virtual drives.
::Type PSUBST drive1: /P to restore a virtual drive from persistency.
@echo off


if "%~1" == "/?" goto :print_usage


if "%~1" == "" (
	rem
	rem SUBST
	rem

	subst

	goto :EOF
)


if /i "%~1" == "/P" (
	rem
	rem SUBST /P
	rem

	setlocal

	call :psubst_init

	call :psubst_print

	endlocal
	goto :EOF
)


setlocal

call :psubst_init

call :psubst_check_disk "%~1" || exit /b %ERRORLEVEL%

if /i "%~2" == "/P" (
	rem
	rem PSUBST X: /P
	rem

	call :psubst_lookup "%psubst_disk%"
	if not defined psubst_persist_path (
		echo:%~n0: Drive not persistent
		exit /b 1
	)

	setlocal enabledelayedexpansion

	subst "!psubst_persist_disk!" "!psubst_persist_path!"

	endlocal
	goto :EOF
)

if /i "%~2" == "/D" (
	rem
	rem PSUBST X: /D ...
	rem

	set "psubst_reg_op=delete"
	set "psubst_path="
) else (
	rem
	rem PSUBST X: "..." ...
	rem

	call :psubst_check_path "%~2" || exit /b %ERRORLEVEL%
)

if /i "%~3" == "/P" (
	rem
	rem PSUBST ... /P
	rem

	call :psubst_persist "%~3"
) else if /i "%~3" == "/PF" (
	rem
	rem PSUBST ... /PF
	rem

	call :psubst_persist "%~3"
) else if defined psubst_path (
	rem
	rem SUBST X: "..."
	rem

	subst "%psubst_disk%" "%psubst_path%"
) else (
	rem
	rem SUBST X: /D
	rem

	subst "%psubst_disk%" /D
)

endlocal
goto :EOF


:psubst_init
set "psubst_disk="
set "psubst_path="
set "psubst_value="
set "psubst_persist_disk="
set "psubst_persist_path="
set "psubst_reg_op="
set "psubst_regkey=HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\DOS Devices"
goto :EOF


:psubst_check_disk
if not "%~1" == "" for %%d in ( "%~1" ) do if /i "%%~d" == "%%~dd" (
	set "psubst_disk=%%~d"
	exit /b 0
)

echo:%~n0: Invalid parameter: %~1
exit /b 1


:psubst_check_path
if /i "%~1" == "/D" (
	set "psubst_reg_op=delete"
	set "psubst_path="
	exit /b 0
)

if not "%~1" == "" for %%f in ( "%~1\." ) do if exist %%~sf\nul (
	set "psubst_reg_op=add"
	set "psubst_path=%%~ff"
	exit /b 0
)

echo:%~n0: Path not found: %~1
exit /b 1


:psubst_persist
call :psubst_lookup "%psubst_disk%"

if /i "%psubst_reg_op%" == "add" if defined psubst_persist_disk (
	echo:%~n0: Drive already SUBSTed persistently
	exit /b 1
)

if /i "%psubst_reg_op%" == "delete" if not defined psubst_persist_disk (
	echo:%~n0: Drive not SUBSTed persistently
	exit /b 1
)

set "psubst_value="

if /i "%~1" == "/PF" (
	call :psubst_persist_reg_sudo
) else (
	call :psubst_persist_reg
)

call :psubst_lookup "%psubst_disk%"

if /i "%psubst_reg_op%" == "add" if not defined psubst_persist_disk (
	echo:%~n0: Unable to add persistently SUBSTed drive
	exit /b 1
)

if /i "%psubst_reg_op%" == "delete" if defined psubst_persist_disk (
	echo:%~n0: Unable to delete persistently SUBSTed drive
	exit /b 1
)
goto :EOF

:psubst_persist_reg
if defined psubst_path set "psubst_value=/t REG_SZ /d "\??\%psubst_path%""
reg %psubst_reg_op% "%psubst_regkey%" /v %psubst_disk% %psubst_value% /f >nul
goto :EOF

rem Based on the solution suggested in this thread:
rem https://www.dostips.com/forum/viewtopic.php?f=3&t=9212
:psubst_persist_reg_sudo
if defined psubst_path set "psubst_value=/t REG_SZ /d \"\??\%psubst_path%\""
reg add "HKCU\Software\Classes\.elevate\shell\runas\command" /ve /d "cmd.exe /c start reg %psubst_reg_op% \"%psubst_regkey%\" /v %psubst_disk% %psubst_value% /f >nul" /f >nul

type nul > "%TEMP%\%~n0.elevate"
"%TEMP%\%~n0.elevate"
del /q "%TEMP%\%~n0.elevate"

reg delete "HKCU\Software\Classes\.elevate" /f >nul

goto :EOF


:psubst_print
setlocal
call :psubst_lookup
endlocal
goto :EOF


:psubst_lookup
set "psubst_persist_disk="
set "psubst_persist_path="

for /f "tokens=1,2,*" %%a in ( 'reg query "%psubst_regkey%"' ) do ^
for /f "tokens=1,* delims=\\" %%k in ( "%%~c" ) do ^
if "%%k" == "??" if "%~1" == "" (
	echo:%%~a\: =^> %%~l
) else if /i "%~1" == "%%~a" (
	set "psubst_persist_disk=%%~a"
	set "psubst_persist_path=%%~l"
	goto :EOF
)
goto :EOF


:print_usage
for /f "tokens=* delims=:" %%s in ( 'findstr "^::" "%~f0"' ) do echo:%%s
goto :EOF


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