Переменные среды windows server 2008

5.7. Managing Environment Variables with the Set Command

The term environment variable
is foreign to many users because environment variables work in the
background to make life easier for both GUI users and those who work at
the command line. Admittedly, someone working at the command line is
more likely to see the effects of environment variables directly. For
example, without a proper path environment variable, you can’t execute
many applications. The path points to the locations where the command
processor should look for applications.

Windows supports
two forms of environment variables: permanent and session. The session
environment variables only affect the current command line session. As
soon as you close the command window, these environment variables are
gone. You create session environment variables using the Set
command. Permanent environment variables exist for all Windows GUI
applications as well as the command prompt. Unless you change them,
permanent environment variables exist between reboots of your system as
well. You set permanent environment variables using the WMIC Environment
alias . For example, if you want to set the permanent path variable to include the C:\Temp directory, you would type WMIC Environment Where Name=»Path» SET VariableValue=»C:\Temp;%PATH%» and press Enter. Notice that you include the %PATH% expansion variable to preserve the existing path information.

When you work at the command line, you often need environment variables in addition to those Windows uses. For example, the COPYCMD
environment variable affects the Copy, Move, and XCopy utilities. You
can set the command line switches you want to use with these utilities
by setting the COPYCMD environment
variable. Of course, you can always override your selections by
specifying a different set of command line switches at the command line.
For example, if you set the /Y command line switch in the COPYCMD environment variable, you can override it by specifying the /-Y command line switch.

Many environment variables only affect one application. For example, you can set the MORE
environment variable to set the command line switches for the More
utility. Every time you use the More utility, it searches for this
environment variable and sets itself up accordingly.

Command line
environment variables need not impose on those used in Windows. Besides
setting environment variables in the Environment Variables dialog box
and at the command line using the Set command, you can add environment variables to the AutoExec.NT file. Windows executes the commands within AutoExec.NT
every time it opens a command prompt for you. These environment
variables appear every time you open a command prompt, but won’t appear
within Windows. 

For all of the tasks that it performs, the Set command is relatively simple. This command uses the following syntax:

SET [variable[=[string]]]
SET /A expression
SET /P variable=[promptString]

The following list describes each of the command line arguments.

variable

Specifies
the environment variable name. The name can’t contain spaces or most
special characters. You can split words in a variable name using the
underscore (_) or dash (-).

string

Defines the value of the environment variable. If you type the environment variable, followed by an equals sign (=), but without a value, the Set command deletes the environment variable. Type the Set
command followed by the environment variable without an equals sign to
determine the current environment variable value. In fact, you can type
as little as a single letter to see a list of environment variables and
their associated values that begin with that letter.

/A

expression

Creates an
environment variable based on an expression, such as a math equation or
the concatenation of multiple environment variables, instead of a
standard string.

/P

variable=[promptString]

Prompts the user
to assign a value to an environment variable, rather than assigning the
value directly. You must supply a variable name. The optional prompt
string lets you provide a specific prompt to the user. Otherwise, the
display doesn’t show any prompt at all.

Server Core comes with a
number of standard environment variables. These hard-coded environment
variables perform essential tasks, such as displaying the current
directory for you. You can see a list of these environment variables on
the Microsoft Web site at http://www.microsoft.com/resources/documentation/windows/xp/all/proddocs/en-us/ntcmds_shelloverview.mspx. Typing Set by itself and pressing Enter displays the list of environment variables set for your machine as shown in Figure 2. This list doesn’t include the hard-coded environment variables such as CD.

You can use the /A
command line switch to combine existing environmental variables or even
perform math with them. For example, you could use the following Set command to create a new environment variable based on the existing %NUMBER_OF_PROCESSORS% environment variable.

SET /A TwiceTheProcessor=%NUMBER_OF_PROCESSORS% * 2

Figure 2. The Set command displays the list of environment variables defined for your machine.

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You can use any of the operators shown in Table 4 when creating your expression. The operators appear in order of precedence.

Table 4. Set Expression Operators

Any expressions you
create can also contain octal, decimal, or hexadecimal numbers. All
octal values begin with a 0 (zero) and hexadecimal values begin with a
0x. 

5.8. Managing Environment Variables with the SetX Utility

The SetX utility performs essentially the same tasks as the Set command . However, it offers considerably more
flexibility because you can use SetX over a network to interact with
variables on other machines. In addition, it offers considerable
flexibility in setting variables, such as letting you choose between the
current user and the system as a whole. Rather than repeat all of the
common information for using SetX, please refer to the Set command as a starting point. This command uses the following syntax:

SETX [/S system [/U [domain\]user [/P [password]]]] var value [/M]
SETX [/S system [/U [domain\]user [/P [password]]]] var /K regpath [/M]
SETX [/S system [/U [domain\]user [/P [password]]]] /F file {var
   {/A x,y | /R x,y string}[/M] | /X} [/D delimiters]

The following list describes each of the command line arguments.

/S

system

Specifies the remote system that you want to check. In most cases, you’ll also need to supply the /U and the /P command line switches when using this switch.

/U

[domain\]user

Specifies the
username on the remote system. This name may not match the username on
the local system. You’ll need to supply a domain name when working with a
domain controller.

/P

[password]

Specifies the
password for the given user. You can provide the command line switch
without specifying the password on the command line in cleartext. The
system prompts you for the password. Using this feature can help you
maintain the security of passwords used on your system.

var

Contains the name of the variable you wish to change.

value

Sets the specified
variable to the supplied value. You don’t have to provide the equals
sign (=) as you do when working with the Set command. Place values with spaces within double quotes.

/M

Sets the value as a system-wide (machine-level) variable that appears in HKEY_LOCAL_MACHINE. The default setting places the variable within the current user’s environment.

/K

regpath

Sets the
specified variable using the content of a registry key. You must provide
the fully qualified registry value (including all of the keys), such as
KEY_LOCAL_MACHINE\System\CurrentControlSet\Control\TimeZoneInformation\StandardName.

/F

file

Specifies the name
of a text file to use for settings. You must also provide the position
of the setting within the file as an absolute or relative coordinate
(line number and character position). In addition, if the setting is
delimited, you must provide the delimiter used for it.

/A

x,y

Provides the
absolute position of the setting within the file. You must provide the
position as a line number and character number.

/R

x,y string

Provides a
relative position of the setting within the file. SetX first searches
for the string you specify within the file. It then moves relative to
that string the number of lines and characters within the line that you
specify.

/X

Displays the
file contents using x and y coordinates. This argument doesn’t actually
set any variables. What it does is display the position of each
potential setting within the file so that you can use the /A and /R arguments with greater ease.

/D

delimiters

Defines the
delimiters used to begin and end settings entries within the file. The
default settings include space, tab, carriage return, and linefeed. You
can use any ASCII character as a delimiter. The maximum number of
delimiters, including the default delimiters, is 15.

5.9. Executing Applications Using the Start Command

A common way to handle this problem, when the application supports
it, is to ask it to return immediately and continue working in the
background. The only problem with this approach is that you aren’t sure
that the command or utility completed successfully. The Start
command helps you overcome this problem by creating a new window for
the command or window to run in. The command or utility still controls
the command prompt until it completes, but since it runs in another
window, the user can continue working.

Another use for this
utility is to start the command or utility in a window with a specific
title. You can apply settings to a window that rely on the window title . Whenever you open a window with that title, it also has
the special formatting that you specified. In short, you can create
custom environments in which to run a utility. This utility uses the
following syntax:

START ["title"] [/Dpath] [/I] [/MIN] [/MAX] [/SEPARATE | /SHARED] [/LOW
   | /NORMAL | /HIGH | /REALTIME | /ABOVENORMAL | /BELOWNORMAL] [/WAIT]
   [/B] [{command | program}] [parameters]

The following list describes each of the command line arguments.

«title»

Defines the title of the command window title bar.

/D

Path

Specifies the
starting directory for the command window. This value doesn’t have to
be the same as the path for the command that you want to execute. For
example, it might be the path to the data directory for the command.

/B

Starts the
application without creating a new window. The application executes as a
background task and doesn’t display a user interface. 

/I

Passes the
standard command environment to the new window, rather than using any
changes made to the command environment by the current command window.
Using this command line switch ensures that the application won’t run in
a contaminated environment where an environmental setting could
adversely affect the way the application runs.

/MIN

Starts the application with the command window minimized.

/MAX

Starts the application with the command window maximized.

/SEPARATE

Starts 16-bit
Windows applications in a separate memory space. Normally, Windows uses a
separate memory space for all 32-bit applications, but a single memory
space for all 16-bit applications. Older applications don’t always use
memory correctly, resulting in memory corruption that can cause other
applications to fail. Using this command line switch eliminates shared
memory corruption problems. However, this feature comes at the cost of
performance and overall system resource usage. Unlike 32-bit memory
spaces, 16-bit memory spaces remain fixed in memory, which uses the
memory inefficiently and causes memory fragmentation. Memory
fragmentation can cause Windows to perform inefficiently, leading to
performance problems. In short, use this command line switch only when
you actually experience problems.

/SHARED

Starts the
16-bit Windows application in a shared memory space. This is the default
setting and you should normally use it unless you experience memory
corruption problems while running the application.

/LOW

Starts the
application in the IDLE priority class. Use this priority setting for
applications that only run when other applications don’t require the
processor. This command line switch helps the system function more
efficiently when you want to run the application as a background task
and don’t care when it completes its work.

/BELOWNORMAL

Starts the
application in the BELOWNORMAL priority class. Use this priority setting
for background applications that you want to complete in a timely
manner, but not at the expense of foreground applications.

/NORMAL

Starts the
application in the NORMAL priority class. This is the default setting.
Foreground applications normally start at this priority. You should only
use this setting for applications that you want to complete at a normal
pace. This setting does affect all foreground application
responsiveness.

/ABOVENORMAL

Starts the
application in the ABOVENORMAL priority class. This setting places the
application at a slightly higher priority than standard applications.
The other foreground tasks continue to run, but at a noticeably slower
pace. Use this setting for priority applications that must complete
tasks quickly.

/HIGH

Starts the
application in the HIGH priority class. You won’t normally have a good
reason to use this priority for any application. Using this priority
level can affect system functionality and definitely slows other
foreground applications to a crawl. Always use this setting with extreme
caution.

/REALTIME

Starts the
application in the REALTIME priority class. Using this priority level
stops execution of other foreground tasks and some system tasks as well.
In addition, system functionality degrades noticeably. In some
circumstances, the system could actually freeze and require a reboot.
Generally, you don’t want to use this priority for any reason.

/WAIT

Starts the application and waits for it to terminate. This setting ensures that you know when an application completes its task.

{command | program}

Specifies the
internal command/batch file or the external utility/ application to run.
The command window remains visible after you run an internal command or
batch file because the system executes the command processor (CMD.EXE) with the /K switch.  The system runs external utilities and
applications in a window or in a full-screen console. Unless you change
the default behavior using a command line switch, the window or
full-screen console closes when the application completes execution.

parameters

Specifies the parameters (arguments) passed to the command or program.

5.10. Determining the Operating System Version with the Ver Command

The Ver command
is one of the easier commands to use. It doesn’t require any arguments
and provides only one type of output. Whenever you use the Ver
command, you receive the operating system version information. The
version information contains the operating system name in human-readable
form, the major version number, the minor version number, and the build
number. For example, the current Windows XP version at the time of this
writing is Microsoft Windows XP [Version 5.1.2600]. Server Core
displays something like Microsoft Windows [Version 6.0.6001].

5.11. Getting Volume Information with the Vol Command

The Vol
command displays the volume information for the current or selected
drive. The information includes the drive letter, the drive volume name,
and the serial number. This command uses the following syntax:

VOL [drive:]

The following describes the command line argument.

drive Specifies the letter of the drive for which you want to obtain volume information. The default is the current drive.

6. Using Debugging Utilities

The command line is an
admittedly simple place to work from a programming perspective. In fact,
using batch files is more along the lines of working with a very simple
kind of script, rather than a complex application. Even so, you’ll
eventually need to perform some kind of debugging. The debugging may
involve checking inside a file to ensure you aren’t going to execute a
virus. You may also have to perform some low-level tasks with very old
applications to get them to run in the Server Core environment. The
following sections describe the debugging utilities that Server Core
makes available for your use.

6.1. Examining, Modifying, and Debugging Files with the Debug Utility

Microsoft
originally intended the Debug utility to help developers debug assembly
language applications. You can still use the utility for that purpose,
but the number of assembly language programs still in use is very small.
In fact, it’s likely that you’ll never see an application originally
written in assembler.

Fortunately, the Debug
utility does have other purposes. For example, you can use it to view
hidden information in executable files. Application developers leave
many notes inside applications and it’s often helpful to view these
messages when deciding on the alternative uses of a utility. You can
also locate copyright information in files when you want to know more
about the file. Sometimes, you can also use the Debug utility to locate
information in data files or make quick fixes to damaged data files.
Most people refer to this other use for Debug as hex (short for
hexadecimal) editing. However, the Debug utility interface is archaic
and many people find it hard to use. If you need low-level access to
files regularly, you might want to invest in a third-party utility for
the task such as XVI32 . This utility uses the following syntax:

DEBUG [[drive:][path]filename [testfile-parameters]]

The following list describes each of the command line arguments.

[drive:][path]filename

Specifies the name of the file that you want to view, edit, or debug.

testfile-parameters

Specifies
the command line arguments required by the application you want to test.
You never use this second argument to simply view or edit a file.

6.2. Converting Executables with the Exe2Bin Utility

The Exe2Bin
utility converts an application from the Portable Executable (PE) format
to the binary format. The main difference is in how the executable
loads. At some time in the past, you needed to use this utility quite
often to convert executable files because the linkers of the time didn’t
provide the required functionality, but now it’s a relic that you might
never use. The resulting binary file is smaller than the executable and
may execute slightly faster. At a time when developers counted
individual bits, this utility served an important purpose. This utility
uses the following syntax:

EXE2BIN [drive1:][path1]input-file [[drive2:][path2]output-file]

The following list describes each of the command line arguments.

[drive:][path1]input-file

Specifies the
location and name of the EXE file you want to convert. If you don’t
provide drive and path information, the utility assumes that you want to
use the current drive and path.

[drive1:][path1]output-file

Specifies the
location and name of the binary file (usually with a COM extension) that
you want to output. If you don’t provide drive and path information,
the utility assumes that you want to use the current drive and path.

Environment variables are not often seen directly when using Windows. However there are cases, especially when using the command line, that setting and updating environment variables is a necessity. In this series we talk about the various approaches we can take to set them. In this article we look at how to interface with environment variables using the Command Prompt and Windows PowerShell. We also note where in the registry the environment variables are set, if you needed to access them in such a fashion.

Print environment variables

You can use environment variables in the values of other environment variables. It is then helpful to be able to see what environment variables are set already. This is how you do it:

Command Prompt

List all environment variables

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ALLUSERSPROFILE=C:\ProgramData
APPDATA=C:\Users\user\AppData\Roaming
.
.
.
windir=C:\Windows

Print a particular environment variable:

Windows PowerShell

List all environment variables

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Name                           Value
----                           -----
ALLUSERSPROFILE                C:\ProgramData
APPDATA                        C:\Users\user\AppData\Roaming
.
.
.
windir                         C:\Windows

Print a particular environment variable:

Set Environment Variables

To set persistent environment variables at the command line, we will use setx.exe. It became part of Windows as of Vista/Windows Server 2008. Prior to that, it was part of the Windows Resource Kit. If you need the Windows Resource Kit, see Resources at the bottom of the page.

setx.exe does not set the environment variable in the current command prompt, but it will be available in subsequent command prompts.

User Variables

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setx EC2_CERT "%USERPROFILE%\aws\cert.pem"

Open a new command prompt.

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C:\Users\user\aws\cert.pem

System Variables

To edit the system variables, you’ll need an administrative command prompt. See HowTo: Open an Administrator Command Prompt in Windows to see how.

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setx EC2_HOME "%APPDATA%\aws\ec2-api-tools" /M

Warning This method is recommended for experienced users only.

The location of the user variables in the registry is: HKEY_CURRENT_USER\Environment. The location of the system variables in the registry is: HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment.

When setting environment variables through the registry, they will not recognized immediately. One option is to log out and back in again. However, we can avoid logging out if we send a WM_SETTINGCHANGE message, which is just another line when doing this programatically, however if doing this on the command line it is not as straightforward.

One way is to get this message issued is to open the environment variables in the GUI, like we do in HowTo: Set an Environment Variable in Windows — GUI; we do not need to change anything, just open the Environment Variables window where we can see the environment variables, then hit OK.

Another way to get the message issued is to use setx, this allows everything to be done on the command line, however requires setting at least one environment variable with setx.

Printing Environment Variables

With Windows XP, the reg tool allows for accessing the registry from the command line. We can use this to look at the environment variables. This will work the same way in the command prompt or in powershell. This technique will also show the unexpanded environment variables, unlike the approaches shown for the command prompt and for powershell.

First we’ll show the user variables:

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reg query HKEY_CURRENT_USER\Environment

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HKEY_CURRENT_USER\Environment
    TEMP    REG_EXPAND_SZ    %USERPROFILE%\AppData\Local\Temp
    TMP    REG_EXPAND_SZ    %USERPROFILE%\AppData\Local\Temp

We can show a specific environment variable by adding /v then the name, in this case we’ll do TEMP:

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reg query HKEY_CURRENT_USER\Environment /v TEMP

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HKEY_CURRENT_USER\Environment
    TEMP    REG_EXPAND_SZ    %USERPROFILE%\AppData\Local\Temp

Now we’ll list the system environment variables:

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reg query "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment"

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HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
    ComSpec    REG_EXPAND_SZ    %SystemRoot%\system32\cmd.exe
    FP_NO_HOST_CHECK    REG_SZ    NO
    NUMBER_OF_PROCESSORS    REG_SZ    8
    OS    REG_SZ    Windows_NT
    Path    REG_EXPAND_SZ    C:\ProgramData\Oracle\Java\javapath;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\
    PATHEXT    REG_SZ    .COM;.EXE;.BAT;.CMD;.VBS;.VBE;.JS;.JSE;.WSF;.WSH;.MSC
    PROCESSOR_ARCHITECTURE    REG_SZ    AMD64
    PROCESSOR_IDENTIFIER    REG_SZ    Intel64 Family 6 Model 60 Stepping 3, GenuineIntel
    PROCESSOR_LEVEL    REG_SZ    6
    PROCESSOR_REVISION    REG_SZ    3c03
    PSModulePath    REG_EXPAND_SZ    %SystemRoot%\system32\WindowsPowerShell\v1.0\Modules\;C:\Program Files\Intel\
    TEMP    REG_EXPAND_SZ    %SystemRoot%\TEMP
    TMP    REG_EXPAND_SZ    %SystemRoot%\TEMP
    USERNAME    REG_SZ    SYSTEM
    windir    REG_EXPAND_SZ    %SystemRoot%

And same as with the user variables we can query a specific variable.

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reg query "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v PATH

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HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment
    PATH    REG_EXPAND_SZ    C:\ProgramData\Oracle\Java\javapath;C:\WINDOWS\system32;C:\WINDOWS;C:\WINDOWS\System32\Wbem;C:\WINDOWS\System32\WindowsPowerShell\v1.0\;%SystemRoot%\system32;%SystemRoot%;%SystemRoot%\System32\Wbem;%SYSTEMROOT%\System32\WindowsPowerShell\v1.0\

Unsetting a Variable

When setting environment variables on the command line, setx should be used because then the environment variables will be propagated appropriately. However one notable thing setx doesn’t do is unset environment variables. The reg tool can take care of that, however another setx command should be run afterwards to propagate the environment variables.

The layout for deleting a user variable is: reg delete HKEY_CURRENT_USER\Environment /v variable_name /f. If /f had been left off, we would have been prompted: Delete the registry value EXAMPLE (Yes/No)?. For this example we’ll delete the user variable USER_EXAMPLE:

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reg delete HKEY_CURRENT_USER\Environment /v USER_EXAMPLE /f

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The operation completed successfully.

Deleting a system variable requires administrator privileges. See HowTo: Open an Administrator Command Prompt in Windows to see how to do this.

The layout for deleting a system variable is: reg delete "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v variable_name /f. For this example we’ll delete the system variable SYSTEM_EXAMPLE:

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reg delete "HKEY_LOCAL_MACHINE\SYSTEM\CurrentControlSet\Control\Session Manager\Environment" /v SYSTEM_EXAMPLE /f

If this was run as a normal user you’ll get:

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ERROR: Access is denied.

But run in an administrator shell will give us:

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The operation completed successfully.

Finally we’ll have to run a setx command to propagate the environment variables. If there were other variables to set, we could just do that now. However if we were just interested in unsetting variables, we will need to have one variable left behind. In this case we’ll set a user variable named throwaway with a value of trash

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SUCCESS: Specified value was saved.

Resources

• Windows XP Service Pack 2 Support Tools
• Windows Server 2003 Resource Kit Tools
• Reg — Edit Registry | Windows CMD | SS64.com
• Reg — Microsoft TechNet
• Registry Value Types (Windows) — Microsoft Windows Dev Center
• How to propagate environment variables to the system — Microsoft Support
• WM_SETTINGCHANGE message (Windows) — Microsoft Windows Dev Center
• Environment Variables (Windows) — Microsoft Windows Dev Center

Windows Server 2003 Resource Kit Tools will also work with Windows XP and Windows XP SP1; use Windows XP Service Pack 2 Support Tools with Windows XP SP2. Neither download is supported on 64-bit version.

Parts in this series

• HowTo: Set an Environment Variable in Windows

• HowTo: Set an Environment Variable in Windows — GUI

• HowTo: Set an Environment Variable in Windows — Command Line and Registry

• Home
•  » 
• Operating System
•  » 
• Command line references

Introduction

Path command in Windows Server 2008 is used to sets the command path in PATH environment variable. Syntax used for Path command is given below.

Syntax

Parameter For Path

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