FileOpen in a not permitted directory

Hello!

I tried to use the following script to determine, wether the user has the permission to write into the installation directory or not.

Function OnDirLeave

  ClearErrors

  SetOutPath $INSTDIR

  

  FileOpen $0 "test.dat" "w"

  ;StrCmp $0 "" notPossible possible

  IfErrors notPossible possible

  



notPossible:

  MessageBox MB_OK "Not able to write into this directory!"

  Abort

possible:

  FileClose $0

FunctionEnd

According to the helpfile and what I'm used to when working with files under windows, it should have worked, what means, that FileOpen should not have worked.

But it did! Checking the permissions with this function failed!

So I tried the following one, which solved the problem:

Function OnDirLeave

  ClearErrors

  SetOutPath $INSTDIR

  

  FileOpen $0 "test.dat" "w"

  FileWriteByte $0 "0"

  IfErrors notPossible possible

  

notPossible:

  MessageBox MB_OK "Not able to write into this directory!"

  Abort

possible:

  FileClose $0

  Delete "$INSTDIR\test.dat"

FunctionEnd

Now my question is, if anyone can explain to me, why the first version didn't work!

TIA
Christian

P.S.: Please excuse my poor english!