!define REALPATH "C:\lobolunar\fakepath"

Name "Parents"
OutFile "Parent.exe"

Function GetParent
Exch $R0
Push $R1
Push $R2
Push $R3
StrCpy $R1 0
StrLen $R2 $R0
loop:
IntOp $R1 $R1 + 1
IntCmp $R1 $R2 get 0 get
StrCpy $R3 $R0 1 -$R1
StrCmp $R3 "\" get
Goto loop
get:
StrCpy $R0 $R0 -$R1
Pop $R3
Pop $R2
Pop $R1
Exch $R0
FunctionEnd

Function ".onInit"
Push "${REALPATH}"
Call GetParent
Pop $R0
MessageBox MB_OK "Real Path: ${REALPATH} $\r$\nThe parent path: $R0"
Quit
FunctionEnd

Section "-boo"
;Nada
SectionEnd