o_cee
19th September 2002 18:21 UTC

Determine if a file is in use
What would be the best way to determine if a file (.dll) is in use (by the shell) or not?

Will FileOpen (W) always fail if the file is in use? Is that the quickest way?


thanks

o_cee

kichik
19th September 2002 18:27 UTC

As far as I know every shell DLL (COM as a matter of fact) has an exported function called DllCanUnloadNow. Use an external DLL to call it and see if it can be unloaded, which means it can be deleted (I think).

http://msdn.microsoft.com/library/de...f_d2l_531z.asp

o_cee
20th September 2002 09:19 UTC

Seems very useful. I'll have to ask a friend to make a suitable dll for me since i don't code myself :)

Thanks


o_cee

o_cee
23rd September 2002 06:48 UTC

Could the new system.dll plugin be used for this? If yes, how?


thanks

o_cee

brainsucker
23rd September 2002 09:50 UTC

;)
Yes, but I surely should develop a new documentation :)

Ok. At first, you should use the latest CVS snapshot or snapshoted release (from sept.22), because the order of arguments changed in this release.

There are two pathways: first does the direct check, while the second allows you to check if the dll available and contains the DllCanUnloadNow.

1) System::FullCall "shell32.dll?DllCanUnloadNow?i" "?0"
; Now you can do the check, for example with StrCmp

shell32.dll should be replaced with your dll (it can include path).
"?0" should be replaced with desired output register ('?s' for stack, '?n' for $n, '?N', where N='a'..o for $Rn).
After that you can check it with StrCmp, for example
StrCmp $0 0 Can Cant
There is no error, S_OK==0 and S_CANCEL==1, so 0 return value means YES, you can :)

2) System::FullAddr "shell32.dll?DllCanUnloadNow?i" "?1"
Pop $0
StrCmp $0 0 0 DllFound
MessageBox MB_OK "Dll not found or it contains no DllCanUnloadNow"
Quit ; Or whatever you want
DllFound:
System::Call $0
; Now you can do the check, for example with StrCmp
; And at last, if you are not going to confuse Windows
System::Free $0

All comments for previous section are the same... And be carefull, this code uses "?1" so you should check $1, not $0.