Display directory from delphi

Question

I would like to display the contents of a directory using DOS commands from Delphi(7). Using Win10 - 64

The following program displays the DOS shell but does not display the directory contents. What is wrong with my code ?

unit Unit1;
interface
uses
Windows, Messages, SysUtils, Variants, Classes, Graphics, Controls, Forms,
Dialogs, StdCtrls, shellapi;
type
  TForm1 = class(TForm)
    procedure FormCreate(Sender: TObject);
  private
    { Private declarations }
  public
    { Public declarations }
  end;
var
  Form1: TForm1;

  implementation

{$R *.dfm}

procedure TForm1.FormCreate(Sender: TObject);
var i : integer;
begin
   i := ShellExecute(Handle, nil, 'cmd.exe', PChar(' dir'), nil, SW_SHOW);
   caption := inttostr(i);
end;

end.

If your question is about Delphi, why isn't there a Delphi tag? And DOS died more than a decade ago, so you can't be running a DOS command (unless you're still running Windows XP or earlier). — Ken White, Nov 02 '16 at 00:01
DOS as an OS is long dead, but `cmd.exe` as a command processor still exists in modern Windows versions. But the real question is, why use `cmd.exe` to get a directory listing instead of using a `FindFirst/Next()` loop, or a GUI component like `TDirectoryListBox` (or modern replacement). — Remy Lebeau, Nov 02 '16 at 00:36

score 5 · Answer 1 · edited Nov 02 '16 at 10:35

Running your code on Windows 10 returns 2, which is ERROR_FILE_NOT_FOUND.

I got it to work, on both 32- and 64-bit target platforms, by changing it to this:

var
  ComSpec: string;
  retval: HINSTANCE;
begin
  ComSpec := GetEnvironmentVariable('comspec');
  retval := ShellExecute(Handle, nil, PChar(comspec), '/k dir', nil, SW_SHOW);
  if retval <= 32 then
    Caption := Format('Error, return value = %d', [retval])
  else
    Caption := 'Success';
end;

The /k says to run a new instance of cmd.exe and keep the window open. For more details, run cmd /? from a command prompt.

Note that the error handling of ShellExecute is very limited. If you wish to check for errors comprehensively then you must use ShellExecuteEx instead.

Note that many of the error codes returned by `ShellExecute()` are not standard Win32 error codes. In this particular case, it happens that `ShellExecute()`'s error 2 does mean "file not found". If you need to rely on individual error codes, it is better to use `ShellExecuteEx()` instead, since it uses `GetLastError()` for reporting its error code. — Remy Lebeau, Nov 02 '16 at 00:43

Display directory from delphi

1 Answers1