Special windows variables

Some fragmented windows-related notes (mostly admin stuff)

TODO: Cleanup

✎ This article/section is a stub — some half-sorted notes, not necessarily checked, not necessarily correct. Feel free to ignore, or tell me about it.

Environment variables

Program stuff

Program Files (%PROGRAMFILES%, and see also %PROGRAMFILES(X86)%)

considered read-only for regular users (it's a system account that does actual installation(verify))

ProgramData (%PROGRAMDATA%, apparently also %SystemDrive%\ProgramData and %ALLUSERSPROFILE%)

data that a program needs, yet which is not user-specific (it's not part of user profiles)

might be writable to users in home installs

but AD-style workstation setups (where software install is managed for you) might choose to lock this down

that lockdown is often done in a way where only users that created a file can read back the same files, so even if you seem to be able to create files there, it won't let you do things like configurations shared between users

so programs shouldn't count on sharing data here

some programs may use this for install-time configurations stuff and afterwards treat it as read-only - but others do not

something you would consider 'supporting data' might frankly be here or in Program files (in fact, Program Files might have more refined ACLs more aware of installers)

User profile stuff

%USERPROFILE%

AppData (under %USERPROFILE%\AppData)

data required by applications, like configuration, caches, etc.

there is little keeping you from putting those elsewhere under userprofile, but it's generally here

Split into Local, Roaming, and LocalLow (see below)

%APPDATA% seems to expands to %USERPROFILE%\AppData\Roaming (has since Vista? Was it always to Roaming, though?)

%LOCALAPPDATA% expands to %USERPROFILE%\AppData\Local (since when?)

a few programs choose to install completely to AppData (typically \Local)

%HOMESHARE% (and the related %HOMEDRIVE% and %HOMEPATH% (which should always be directly appended?))

HOMESHARE is comparable to USERPROFILE

HOMESHARE is set later than USERPROFILE[1]

isn't necessarily the same as %USERPROFILE%

This can get messy to understand. For example, in one AD-managed setup I used,

%HOMESHARE% points to a \\network path that contains all my files, and the contents of %USERPROFILE% are not synchronized

%USERPROFILE% is a mostly-empty directory tree on the local disk (presumably because windows says this directory has to exist?)

...yet many (but not all) entires within that USERPROFILE are actually junctions to the path that HOMESHARE points to

in a way that is very hard to explain to non-nerds. For example, DIR is a Documents that is local, a My Documents that is is a junction - and that explorer also shows as Documents (without the My)

(note: you can see the presence of junctions e.g. using DIR /A, or mostly them with /AL)

Notes

Roaming and Local only serve different function if Roaming is actually synchronized (or remote-mounted?)

if no syncing (or remote-mounting?) is going on, Roaming is really just Local as well

it's a good idea for programs to make this distinction just in case you do

Roaming classically only did anything for people in Domain environments.

Since Windows 8, windows might synchronize between different MS logins (verify)

Local is for things that should not roam with the user, even if it could.

e.g. most caches

LocalLow - The idea of "Low integrity environments" is to make put stuff there that is easier to distrust -- or rather, makes it easier to set up rules/filters for that set of software, letting you restrict them to all but a few directories. This is mainly aimed at browsers, because they are a common attack vector.

in practive, LocalLow may point to the same folder as Local, or may not.

https://helgeklein.com/blog/internet-explorer-in-protected-mode-how-the-low-integrity-environment-gets-created/

Special windows variables

Contents

Environment variables

Program stuff

User profile stuff

Known Folders, Special Folders

CSIDL

Unsorted

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