show available drives [SOLVED]
lazarus / 67-Windows

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bjlockie1 · 2020-11-20 21:20

I'm trying to list available drives.
These functions show 3 letters, C, D, Z.
It can't ChDir to drive D:\ but C:\ and Z:\ work fine.
I don't think drive D: should be listed.
I am not a Windows programmer so I cobbled this code together.


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
GetBit(Value: QWord; Index: Byte): Boolean;begin  Result := ((Value
shr Index) and 1) = 1;end; function GetDriveLetters():
TStringList;{$ifdef Windows}var dword     : QWord;    letter    :
Char;    i         : Byte = 0;    shortname : String;{$endif}begin   
Result:=TStringList.Create();    {$ifdef Windows}       
dword:=GetLogicalDrives();         for letter:='A' to 'Z' do       
begin            if GetBit(dword,i)=True then            begin       
       shortname:='(DRIVE) '+letter+':\';                Result.Add(
shortname );            end;            i:=i+1;        end;   
{$endif}end;

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Remy Lebeau · 2020-11-20 21:24

Quote from: bjlockie1 on November 20, 2020, 10:20:24 pmIt can't ChDir
to drive D:\ but C:\ and Z:\ work fine.

What kind of drive is D:\ exactly?  What does GetDriveType() report
for it?  Is it a partition on an HDD/SSD?  Is it a CD/DVD disc drive? 
Is it a removable USB drive?  Is it a network drive share?

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440bx · 2020-11-21 01:12

Quote from: bjlockie1 on November 20, 2020, 10:20:24 pmI'm trying to
list available drives.
These functions show 3 letters, C, D, Z.
It can't ChDir to drive D:\ but C:\ and Z:\ work fine.
I don't think drive D: should be listed.
The fact that Windows allocated a letter to a drive does not always
imply the drive is accessible.  That's why @Remy Lebeau above was
asking for the drive type.

You can find an example of showing the available drives and their type
at https://forum.lazarus.freepascal.org/index.php/topic,44377.msg31191
0.html#msg311910

But, again, the fact that a letter/drive is listed does _not_ mean it
is accessible.

HTH.

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winni · 2020-11-21 01:32

Quote from: bjlockie1 on November 20, 2020, 10:20:24 pmI'm trying to
list available drives.


Why do you start a new topic with the same issue
while the other topic is still active??

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bjlockie1 · 2020-11-21 04:32

Quote from: winni on November 21, 2020, 02:32:58 amWhy do you start a
new topic with the same issue
while the other topic is still active??

The other topic was in the Linux forum.
I said I was coming here to hopefully get more Windows specific help.
Was that wrong?

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bjlockie1 · 2020-11-21 04:34

Quote from: Remy Lebeau on November 20, 2020, 10:24:27 pmQuote from:
bjlockie1 on November 20, 2020, 10:20:24 pmIt can't ChDir to drive D:\
but C:\ and Z:\ work fine.

What kind of drive is D:\ exactly?  What does GetDriveType() report
for it?  Is it a partition on an HDD/SSD?  Is it a CD/DVD drive that
doesn't have a disc in it?  Is it a removable USB drive?


C -> 3
D -> 5
Z -> 4

D is probably an empty cdrom. :-)

Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i function
GetDriveLetters(): TStringList;{$ifdef Windows}var dword     : QWord; 
  letter    : Char;    i         : Byte = 0;    shortname : String;  
dr        : Packed array[0..3] of char;    dt        :
UINT;{$endif}begin    Result:=TStringList.Create();    {$ifdef
Windows}        ZeroMemory(@dr, sizeof(dr));        lstrcpy(dr,
'A:\');             dword:=GetLogicalDrives();         for letter:='A'
to 'Z' do        begin            if GetBit(dword,i)=True then       
   begin                dr[0]:=char(ord('A')+i);               
dt:=GetDriveType(dr);                shortname:='(DRIVE) '+letter+':\'
+ IntToStr(dt);                Result.Add( shortname );           
end;            inc(i);        end;    {$endif}end;

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Bart · 2020-11-21 15:47

I showed you simple code how to do that in https://forum.lazarus.freep
ascal.org/index.php/topic,52203.msg384399.html#msg384399

Use the function GetAvailableDrives(DiskMustBeInDrive: Boolean =
False): TSysCharSet; function.
Set the DiskMustBeInDrive parameter to True.

If there is no disc in the CDRom, it wont be included in the resulting
set.

Bart

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Bart · 2020-11-21 16:44

I'll make it even simpler for you.
Download
http://svn.code.sf.net/p/flyingsheep/code/trunk/MijnLib/fsiwinutils.pp

Now you can do things like this
Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
TForm1.Button1Click(Sender: TObject);var  Drives: TSysCharSet;  D:
Char;begin  writeln('Reported drives by Windows:');  Drives :=
GetAvailableDrives(False);  for D in Drives do writeln(D + ':\','
[',DiskInDrive(D),']');  writeln;  writeln('Actual mounted drives:'); 
Drives := GetAvailableDrives(True);  for D in Drives do writeln(D +
':\');  writeln;  writeln('Removable drives:');  Drives :=
GetAvailableDrives(False, [dtRemovable]);  for D in Drives do
writeln(D + ':\');  writeln;  writeln('CD-Roms''s:');  Drives :=
GetAvailableDrives(False, [dtCDROM]);  for D in Drives do writeln(D +
':\');  writeln;  writeln('Actual mounted CD-Roms''s:');  Drives :=
GetAvailableDrives(True, [dtCDROM]);  for D in Drives do writeln(D +
':\');  writeln;end;[code] For me it outputs:[code]Reported drives by
Windows:C:\ [TRUE]D:\ [TRUE]E:\ [FALSE]F:\ [TRUE] Actual mounted
drives:C:\D:\F:\ Removable drives:F:\ CD-Roms's:E:\ Actual mounted CD-
Roms's: 
Bart

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bjlockie1 · 2020-11-22 01:05

I thought I could wrap ChDir in a try but I still get exception class
'RunError(152)'.


Code: Pascal  [Select][+][-]window.onload = function(){var x1 =
document.getElementById("main_content_section"); if (x1) { var x =
document.getElementsByClassName("geshi");for (var i = 0; i procedure
ChangeDir( dirname : String );begin    try        ChDir( dirname );  
except        ShowMessage('Can''t change to '''+dirname+'''');   
end;end;

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bjlockie1 · 2020-11-22 03:29

I turned off the debugging and ran it from outside the IDE and the try
catches the exception.