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Hack 9 Add, Remove, or Retrieve Environment Variables
Environment variables can easily be added,
removed, or retrieved using the script in this hack.
Using VBScript to work with the
Windows system environment can be pretty simple. This hack shows how
to use a script to read variables, add new variables, remove
variables, and recurse through all of them. Just take a look through
the script and read the comments to see how to perform each task.
Note that there are four types of values in the Windows Script Host
(WSH) environmentSystem, User, Volatile, and Processand
the script uses all of them.
By the way, this script is provided by Dudeworks (http://www.dudeworks.net). For additional
resources on Windows scripting and working with the environment, see
http://msdn.microsoft.com/library/default.asp?url=/library/en-us/script56/html/wsProEnvironment.asp.
The Code
Type the following script into Notepad (with Word Wrap disabled) and
save it with a .vbs extension as
GetEnvVars.vbs:
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
'Created by: Rob Olson - Dudeworks
'Created on: 10/17/2001
'Purpose: Get Environment Variables.
'~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
wscript.echo "Working with the Environment: Provided by www.dudeworks.net"&vbcrlf&vbcrlf&strval
'// Create an instance of the wshShell object
set WshShell = CreateObject("WScript.Shell")
'Use the methods of the object
wscript.echo "Environment.item: "& WshShell.Environment.item("WINDIR")
wscript.echo "ExpandEnvironmentStrings: "& WshShell.ExpandEnvironmentStrings("%windir%")
'// add and remove environment variables
'// Specify the environment type ( System, User, Volatile, or Process )
set oEnv=WshShell.Environment("System")
wscript.echo "Adding ( TestVar=Windows Script Host ) to the System " _
& "type environment"
' add a var
oEnv("TestVar") = "Windows Script Host"
wscript.echo "removing ( TestVar=Windows Script Host ) from the System " _
& "type environment"
' remove a var
oEnv.Remove "TestVar"
'// List all vars in all environment types
'//System Type
set oEnv=WshShell.Environment("System")
for each sitem in oEnv
strval=strval & sItem &vbcrlf
next
wscript.echo "System Environment:"&vbcrlf&vbcrlf&strval
strval="
'//Process Type
set oEnv=WshShell.Environment("Process")
for each sitem in oEnv
strval=strval & sItem &vbcrlf
next
wscript.echo "Process Environment:"&vbcrlf&vbcrlf&strval
strval="
'//User Type
set oEnv=WshShell.Environment("User")
for each sitem in oEnv
strval=strval & sItem &vbcrlf
next
wscript.echo "User Environment:"&vbcrlf&vbcrlf&strval
strval="
'//Volatile Type
set oEnv=WshShell.Environment("Volatile")
for each sitem in oEnv
strval=strval & sItem &vbcrlf
next
wscript.echo "Volatile Environment:"&vbcrlf&vbcrlf&strval
strval="
Running the Hack
To run the script, open a command prompt, change to the directory
where the script is saved, and type cscript.exe
GetEnvVars.vbs. Here is an example of typical output from
the script on a Windows 2000 machine:
Microsoft (R) Windows Script Host Version 5.6
Copyright (C) Microsoft Corporation 1996-2001. All rights reserved.
Working with the Environment: Provided by www.dudeworks.net
Environment.item: %SystemRoot%
ExpandEnvironmentStrings: C:\WINNT
Adding ( TestVar=Windows Script Host ) to the System type environment
removing ( TestVar=Windows Script Host ) from the System type environment
System Environment:
ComSpec=%SystemRoot%\system32\cmd.exe
Os2LibPath=%SystemRoot%\system32\os2\dll;
Path=%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem
windir=%SystemRoot%
OS=Windows_NT
PROCESSOR_ARCHITECTURE=x86
PROCESSOR_LEVEL=6
PROCESSOR_IDENTIFIER=x86 Family 6 Model 5 Stepping 2, GenuineIntel
PROCESSOR_REVISION=0502
NUMBER_OF_PROCESSORS=1
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH
TEMP=%SystemRoot%\TEMP
TMP=%SystemRoot%\TEMP
Process Environment:
=C:=C:=ExitCode=00000000
ALLUSERSPROFILE=C:\Documents and Settings\All Users
APPDATA=C:\Documents and Settings\Administrator\Application Data
CommonProgramFiles=C:\Program Files\Common Files
COMPUTERNAME=SNOOPY
ComSpec=C:\WINNT\system32\cmd.exe
HOMEDRIVE=C:
HOMEPATH=\Documents and Settings\Administrator
LOGONSERVER=\\SNOOPY
NUMBER_OF_PROCESSORS=1
OS=Windows_NT
Os2LibPath=C:\WINNT\system32\os2\dll;
Path=C:\WINNT\system32;C:\WINNT;C:\WINNT\System32\Wbem
PATHEXT=.COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH
PROCESSOR_ARCHITECTURE=x86
PROCESSOR_IDENTIFIER=x86 Family 6 Model 5 Stepping 2, GenuineIntel
PROCESSOR_LEVEL=6
PROCESSOR_REVISION=0502
ProgramFiles=C:\Program Files
PROMPT=$P$G
SystemDrive=C:
SystemRoot=C:\WINNT
TEMP=C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp
TMP=C:\DOCUME~1\ADMINI~1\LOCALS~1\Temp
USERDOMAIN=SNOOPY
USERNAME=Administrator
USERPROFILE=C:\Documents and Settings\Administrator
windir=C:\WINNT
User Environment:
TEMP=%USERPROFILE%\Local Settings\Temp
TMP=%USERPROFILE%\Local Settings\Temp
Volatile Environment:
LOGONSERVER=\\SNOOPY
APPDATA=C:\Documents and Settings\Administrator\Application Data
By the way, if you add a new variable via the command prompt, you
will not see it when you try to read it via the script. You can read
only the new values created via the same scripting type you used to
create them. Although I've tested this only to a
limited extent, it seems to be true. Try it for yourself; just open a
command prompt, type Set DUDE=Dudeworks, and press
Enter to set the new environment variable. Now, when you execute
GetEnvVars.vbs, and you'll
notice that it does not list that new variable.
However, if you type SET at the command prompt,
you will see it.
Rob Olson
