How to detect unused drive letters?

[emendelson]

I'm writing a script which will use the SUBST command to assign a drive letter to a folder on disk. Is there a convenient way to detect which drive letters are currently NOT in use on the current system, so that I can choose one of those letters to use with SUBST? If so, could some generous person tell me what it is?

Many thanks for any help.

[GEOSoft]

Here is one method but it's probably not the best.

#Include<array.au3>
$aDrives = DriveGetDrive("all")

Local $sStr = ""
For $i = 97 To 122
    _ArraySearch($aDrives, Chr($i) & ":")
    If NOT @Error Then Continueloop
    $sStr &= Chr($i) & ":|"
Next
MsgBox(0, "Result", $sStr)

Then You can do what you want with the resulting string, for example split it to get an array.

$aAvailable = StringSplit(stringTrimRight($sStr, 1), "|")

[emendelson]

Here is one method but it's probably not the best.

I don't know if it's the best, but it definitely gets the job done, and that's exactly what I was looking for. Thank you!

[GEOSoft]

Glad it helped but as an after-thought, I'm not sure that doing Subst on A: or B: is such a wise idea so I would do

For $i = 99 To 122

And since C: is invariably used then it would be

For $i = 100 To 122

Just food for thought.

Edited October 9, 2010 by GEOSoft

[emendelson]

That's almost exactly what I did. Thank you.

It's actually possible to have a system with no drive C:. Example: Start with an empty hard disk and use a third-party utility to divide the disk into two primary partitions. Install XP on drive C, using the first primary partition; install Windows 7 on drive D, using the other partition. Then using a third-party utility, delete the XP partition, and make the Windows 7 partition the active one. (Also, optionally, expand the Windows 7 partition to fill the space made available by the removed C: partition, though this is NOT required.) Insert the Windows 7 installation DVD and repair the existing Windows 7 installation. The result is a Windows 7 system with only drive D:

I had a Drive D:-only system years ago. I added XP on drive D: to a Windows 98 system on drive C:, and eventually removed the Windows 98 partition. Windows XP was happy to work on a D:-only system, but an amazing number of applications insisted on writing to drive C:, which didn't exist. So I finally gave up and started over with XP on drive C: (Modern software typically doesn't expect to see a drive C:, fortunately.)

Edited October 9, 2010 by Edward Mendelson

[Danny35d]

Here is another method

MsgBox(0, 'Free drive letter ', _GetFreeDriveLetter())

Func _GetFreeDriveLetter()
    For $x = 67 To 90
        If DriveStatus(Chr($x) & ':\') = 'INVALID' Then Return(Chr($x) & ':')
    Next
EndFunc

[emendelson]

Very nice! Thank you!

[cengizhan]

I have modified your code because it didnt give correct results under windows 7. Here it is:

MsgBox(0, 'Free drive letter ', _GetFreeDriveLetter())

Func _GetFreeDriveLetter()
    For $x = 67 To 90
        If DriveStatus(Chr($x) & ':\') = 'INVALID' or Not FileExists (Chr($x) & ":\") Then Return(Chr($x) & ':')
    Next
EndFunc