How do I run a command-line program in Delphi?

Variant 1 (using the "advanced" CreateProcess):

This will run a 'DOS' program and retrieve its output:

function GetDosOutput(CommandLine: string; Work: string = 'C:\'): string;  { Run a DOS program and retrieve its output dynamically while it is running. }
var
  SecAtrrs: TSecurityAttributes;
  StartupInfo: TStartupInfo;
  ProcessInfo: TProcessInformation;
  StdOutPipeRead, StdOutPipeWrite: THandle;
  WasOK: Boolean;
  pCommandLine: array[0..255] of AnsiChar;
  BytesRead: Cardinal;
  WorkDir: string;
  Handle: Boolean;
begin
  Result := '';
  with SecAtrrs do begin
    nLength := SizeOf(SecAtrrs);
    bInheritHandle := True;
    lpSecurityDescriptor := nil;
  end;
  CreatePipe(StdOutPipeRead, StdOutPipeWrite, @SecAtrrs, 0);
  try
    with StartupInfo do
    begin
      FillChar(StartupInfo, SizeOf(StartupInfo), 0);
      cb := SizeOf(StartupInfo);
      dwFlags := STARTF_USESHOWWINDOW or STARTF_USESTDHANDLES;
      wShowWindow := SW_HIDE;
      hStdInput := GetStdHandle(STD_INPUT_HANDLE); // don't redirect stdin
      hStdOutput := StdOutPipeWrite;
      hStdError := StdOutPipeWrite;
    end;
    WorkDir := Work;
    Handle := CreateProcess(nil, PChar('cmd.exe /C ' + CommandLine),
                            nil, nil, True, 0, nil,
                            PChar(WorkDir), StartupInfo, ProcessInfo);
    CloseHandle(StdOutPipeWrite);
    if Handle then
      try
        repeat
          WasOK := windows.ReadFile(StdOutPipeRead, pCommandLine, 255, BytesRead, nil);
          if BytesRead > 0 then
          begin
            pCommandLine[BytesRead] := #0;
            Result := Result + pCommandLine;
          end;
        until not WasOK or (BytesRead = 0);
        WaitForSingleObject(ProcessInfo.hProcess, INFINITE);
      finally
        CloseHandle(ProcessInfo.hThread);
        CloseHandle(ProcessInfo.hProcess);
      end;
  finally
    CloseHandle(StdOutPipeRead);
  end;
end;

---

Variant 2:

Capture console output in [Realtime] and how it in a TMemo:

procedure CaptureConsoleOutput(const ACommand, AParameters: String; AMemo: TMemo);
 const
   CReadBuffer = 2400;
 var
   saSecurity: TSecurityAttributes;
   hRead: THandle;
   hWrite: THandle;
   suiStartup: TStartupInfo;
   piProcess: TProcessInformation;
   pBuffer: array[0..CReadBuffer] of AnsiChar;      <----- update
   dRead: DWord;
   dRunning: DWord;
 begin
   saSecurity.nLength := SizeOf(TSecurityAttributes);
   saSecurity.bInheritHandle := True;  
   saSecurity.lpSecurityDescriptor := nil; 

   if CreatePipe(hRead, hWrite, @saSecurity, 0) then
   begin    
     FillChar(suiStartup, SizeOf(TStartupInfo), #0);
     suiStartup.cb := SizeOf(TStartupInfo);
     suiStartup.hStdInput := hRead;
     suiStartup.hStdOutput := hWrite;
     suiStartup.hStdError := hWrite;
     suiStartup.dwFlags := STARTF_USESTDHANDLES or STARTF_USESHOWWINDOW;    
     suiStartup.wShowWindow := SW_HIDE; 

     if CreateProcess(nil, PChar(ACommand + ' ' + AParameters), @saSecurity,
       @saSecurity, True, NORMAL_PRIORITY_CLASS, nil, nil, suiStartup, piProcess)
       then
     begin
       repeat
         dRunning  := WaitForSingleObject(piProcess.hProcess, 100);        
         Application.ProcessMessages(); 
         repeat
           dRead := 0;
           ReadFile(hRead, pBuffer[0], CReadBuffer, dRead, nil);          
           pBuffer[dRead] := #0; 

           OemToAnsi(pBuffer, pBuffer);
           AMemo.Lines.Add(String(pBuffer));
         until (dRead < CReadBuffer);      
       until (dRunning <> WAIT_TIMEOUT);
       CloseHandle(piProcess.hProcess);
       CloseHandle(piProcess.hThread);    
     end; 

     CloseHandle(hRead);
     CloseHandle(hWrite);
   end;
end;

Source: delphi.wikia.com

An example using ShellExecute():

procedure TForm1.Button1Click(Sender: TObject);
begin
  ShellExecute(0, nil, 'cmd.exe', '/C find "320" in.txt > out.txt', nil, SW_HIDE);
  Sleep(1000);
  Memo1.Lines.LoadFromFile('out.txt');
end;

Note that using CreateProcess() instead of ShellExecute() allows for much better control of the process.

Ideally you would also call this in a secondary thread, and call WaitForSingleObject() on the process handle to wait for the process to complete. The Sleep() in the example is just a hack to wait some time for the program started by ShellExecute() to finish - ShellExecute() will not do that. If it did you couldn't for example simply open a notepad instance for editing a file, ShellExecute() would block your parent app until the editor was closed.