( See Raymond Chen's explanation of this.) %=C:% The current directory of the C: drive. %_CD_% The current directory, terminated with a trailing backslash. exe, terminated with a trailing backslash. %_APPDIR_% The directory path to the current application. Undocumented Dynamic variables (read only) In PowerShell the same list is available via the env: drive Running the SET command with no options will display all Shell variables plus all User and System Environment variables, in other words every variable available to be read by that session. However, you can use %APPDATA% to build a User environment variable PATH. This precedence is important to understand because if you try to set a System Environment variable PATH = %APPDATA% C:\Windows, it will fail because the %APPDATA% Shell variable is not created until after the System environment variables are imported to the session. When a new process is started, the variables will be loaded in the following order:Īfter the process has started, additional shell variables can be defined with SET, these will be available only to the current CMD shell session, but they will take precedence over any environment variables with the same name.įor example, if the SET command is used to modify the PATH, or if it is removed completely with PATH that will affect the current process, but not any other programs or CMD sessions opened before or after the current one. The majority of volatile variables are CMD shell variables, so like all CMD shell variables they are stored in memory only. Volatile variables are defined under the registry: HKCU\Volatile Environmentĭo not attempt to directly SET a volatile variable, while you could change them, the system will overwrite them with newly derived values. When all variables are listed with SET, these will not appear in the list. System Environment Variables: HKLM\SYSTEM\CurrentControlSet\Control\Session Manager\Environmentīy default, files stored under Local Settings do not roam with a roaming profile.ĭynamic environment variables are computed each time the variable is expanded, this makes them inherently read-only. User Environment Variables: HKCU\Environment %WinDir% pre-dates Windows NT, its use in many places has been replaced by the system variable: %SystemRoot%ġ Only on 64 bit systems, is used to store 32 bit programs.Įnvironment variables are stored in the registry: This is equivalent to the $HOME environment variable in Unix/Linux (This is unlike Parameter variables which only have one % sign and are always one character long: %A )Ī variable name may include any of the following characters:Ī-Z, a-z, 0-9, # $ ' ( ) * ,. The variable name can include spaces, punctuation and mixed case: %_Another Ex.ample% Variables have a percent sign on both sides: %ThisIsAVariable% Variables can be displayed using either SET or Modified and deleted for a session using the SET command. Environment variables are mainly used within batch files, they can be created,
0 Comments
Leave a Reply. |