Windows Path Contract

Winuxsh uses a real Windows directory tree for its Unix-shaped shell paths. This is path spelling support, not MSYS, WSL, Cygwin, a POSIX runtime, or a filesystem overlay.

Ownership

Layer	Responsibility
Winuxsh	Select one `winuxcmd.exe`, derive its installation root, create the real tree, and configure the shell session.
Rubash	Interpret `/`, `/bin`, `/usr/bin`, `/etc`, `/tmp`, `cd`, `source`, glob, redirects, tests, and command lookup.
WinuxCmd	Implement external commands and native Windows filesystem, process, handle, and device operations.
WPM	Install package payloads and command links inside the selected installation root.

Installation Root

For an installed executable such as:

C:/Users/Administrator/AppData/Local/Programs/Winuxsh/winuxcmd/usr/bin/winuxcmd.exe

the shell root is:

C:/Users/Administrator/AppData/Local/Programs/Winuxsh/winuxcmd/
  usr/bin/
  bin/
  usr/local/bin/
  etc/
  var/
  tmp/
  dev/
  .wpm/

These are ordinary Windows directories. usr/bin is canonical for winuxcmd.exe, wpm.exe, command links, and filename-only WPM targets. Explicit WPM targets under bin, usr/bin, or usr/local/bin remain in that exact directory. .wpm is private package state and is never a command path.

Winuxsh passes this exact root to Rubash as WINUXSH_ROOT. Rubash maps paths lexically below it:

/             -> <root>
/usr/bin/tool -> <root>/usr/bin/tool
/bin/tool    -> <root>/bin/tool
/etc/config  -> <root>/etc/config
/tmp/file    -> <root>/tmp/file

Command lookup and native child PATH use these real directories directly. Rubash does not merge a second provider directory, and WinuxCmd coreutils do not inspect Winuxsh variables. Existing flat installations remain usable when their directory is explicitly present on PATH; new installs use the tree above.

Dispatcher Selection

WINUXCMD_PATH selects one exact dispatcher executable for the session. Winuxsh resolves it, prepends that installation's usr/local/bin, usr/bin, and bin directories to the native PATH, and passes the exact executable to Rubash. Rubash does not discover another dispatcher from PATH.

The dispatcher is only a fallback when a command is absent from the real tree. It must not implement Rubash builtins such as cd, export, set, read, jobs, or trap.

Special Paths

~ is USERPROFILE, the same directory used by PowerShell. Windows paths such as C:/work/file and /c/work/file remain host paths.

The only device spelling currently supported is /dev/null, mapped to the native NUL endpoint. Other /dev entries do not become ordinary files until their fd or terminal capability is implemented.