Windows 环境变量

Windows System Environment Variables

These system environment variables are automatically created by Windows upon boot-up in Windows Registry key HKEY_LOCAL_MACHINE\ SYSTEM\ CurrentControlSet\ Control\ Session Manager\ Environment

Variable Sample Typical Value

%SystemDrive% C:

%SystemRoot% C:\WINDOWS

C:\WINNT

%WinDir% C:\WINDOWS

C:\WINNT

%SystemDirectory% C:\WINDOWS\System32

C:\WINNT\System32

%ComSpec% C:\WINDOWS\system32\cmd.exe

The path including the command interpreter program.

%programfiles% C:\WINDOWS\Program Files

%Temp% C:\Users\W\AppData\Local\Temp on Windows Vista & 2008

C:\DOCUME~1\Usr\LOCALS~1\Temp (compressed form of)

C:\Documents and Settings\Usr\Local Settings\Temp

%Tmp%

%HOMEDRIVE% C: The drive letter associated with the user's home directory

%HOMEPATH% The path to the user's home directory as defined in UMD/AD (excluding drive):

\Users\ on Windows Vista & 2008

\Documents and Settings\Guest on Windows XP

%OS% Windows_NT (even on Windows Vista & XP machines

The operating system the user is running

%USERDOMAIN% The name of the domain that contains the user's account. On a stand-alone machine, the same as the machine name.

%USERNAME% The user's name

%USERPROFILE% C:\Users\ — The user's root folder

%USERPROFILE%\Desktop The user's desktop folder

If you have the permissions, invoke, then open my DOS batch file 1envvars.bat which lists the values of these variables on your computer

Windows resolves commands typed in the start/run box first from files in %SYSTEMDRIVE%, then files in %SYSTEMROOT%. This is regardless of the systemdrive (such as E:) being later in the path. This means that a rogue file can be invoked instead of a good file (such as cmd.exe) if it's in the %SYSTEMDRIVE%.

Below are dynamic environment variables:

Variable Sample Typical Value

%CD% The current directory.

%DATE% Current date in the format set by the Date command

%TIME% Current time in the format set by the Time command

%ERRORLEVEL% A number defining exit status of a previous command or called executable.

%RANDOM% A random number between 0 and 32767.

You can quickly reach the folder specified within an environment variable by typing that variable on the Address bar of Windows Explorer:

User Environment Variables Added by Applications

User environment variables are stored in Windows Registry HKEY_CURRENT_USER\Environment

Within a command batch file, to list Oracle Environment Variables

echo ORACLE_SID = %ORACLE_SID%

echo ORACLE_HOME = %ORACLE_HOME%

echo ORA_NLS = %ORA_NLS%

echo.

echo PATH = %PATH%

echo.

echo Machine Name to messenger service:

net name

Novell adds these environment variables during installation.

Variable

%USER%

%NWUSERNAME%

%NWLANGUAGE%

Creating Variables on Windows

Environment Variables can be created and changed using several mechanisms:

By Windows automatically upon boot-up.