src/msw/utilsexc.cpp

   1 /////////////////////////////////////////////////////////////////////////////
   2 // Name:        msw/utilsexec.cpp
   3 // Purpose:     Various utilities
   4 // Author:      Julian Smart
   5 // Modified by:
   6 // Created:     04/01/98
   7 // RCS-ID:      $Id$
   8 // Copyright:   (c) Julian Smart and Markus Holzem
   9 // Licence:     wxWindows license
  10 /////////////////////////////////////////////////////////////////////////////
  11
  12 // ============================================================================
  13 // declarations
  14 // ============================================================================
  15
  16 // ----------------------------------------------------------------------------
  17 // headers
  18 // ----------------------------------------------------------------------------
  19
  20 #ifdef __GNUG__
  21     #pragma implementation
  22 #endif
  23
  24 // For compilers that support precompilation, includes "wx.h".
  25 #include "wx/wxprec.h"
  26
  27 #ifdef __BORLANDC__
  28     #pragma hdrstop
  29 #endif
  30
  31 #ifndef WX_PRECOMP
  32     #include "wx/utils.h"
  33     #include "wx/app.h"
  34     #include "wx/intl.h"
  35 #endif
  36
  37 #include "wx/log.h"
  38
  39 #ifdef __WIN32__
  40     #include "wx/stream.h"
  41     #include "wx/process.h"
  42 #endif
  43
  44 #include "wx/msw/private.h"
  45
  46 #include <ctype.h>
  47
  48 #if !defined(__GNUWIN32__) && !defined(__WXWINE__) && !defined(__SALFORDC__)
  49     #include <direct.h>
  50 #ifndef __MWERKS__
  51     #include <dos.h>
  52 #endif
  53 #endif
  54
  55 #if defined(__GNUWIN32__) && !defined(__TWIN32__)
  56     #include <sys/unistd.h>
  57     #include <sys/stat.h>
  58 #endif
  59
  60 #if defined(__WIN32__) && !defined(__WXWINE__)
  61 #include <io.h>
  62
  63 #ifndef __GNUWIN32__
  64 #include <shellapi.h>
  65 #endif
  66 #endif
  67
  68 #include <stdio.h>
  69 #include <stdlib.h>
  70 #include <string.h>
  71 #ifndef __WATCOMC__
  72     #if !(defined(_MSC_VER) && (_MSC_VER > 800))
  73         #include <errno.h>
  74     #endif
  75 #endif
  76 #include <stdarg.h>
  77
  78 #if wxUSE_IPC
  79     #include "wx/dde.h"         // for WX_DDE hack in wxExecute
  80 #endif // wxUSE_IPC
  81
  82 // ----------------------------------------------------------------------------
  83 // constants
  84 // ----------------------------------------------------------------------------
  85
  86 // this message is sent when the process we're waiting for terminates
  87 #define wxWM_PROC_TERMINATED (WM_USER + 10000)
  88
  89 // ----------------------------------------------------------------------------
  90 // this module globals
  91 // ----------------------------------------------------------------------------
  92
  93 // we need to create a hidden window to receive the process termination
  94 // notifications and for this we need a (Win) class name for it which we will
  95 // register the first time it's needed
  96 static const wxChar *gs_classForHiddenWindow = NULL;
  97
  98 // ----------------------------------------------------------------------------
  99 // private types
 100 // ----------------------------------------------------------------------------
 101
 102 // structure describing the process we're being waiting for
 103 struct wxExecuteData
 104 {
 105 public:
 106     ~wxExecuteData()
 107     {
 108 #ifndef __WIN16__
 109         if ( !::CloseHandle(hProcess) )
 110         {
 111             wxLogLastError(wxT("CloseHandle(hProcess)"));
 112         }
 113 #endif
 114     }
 115
 116     HWND       hWnd;          // window to send wxWM_PROC_TERMINATED to
 117     HANDLE     hProcess;      // handle of the process
 118     DWORD      dwProcessId;   // pid of the process
 119     wxProcess *handler;
 120     DWORD      dwExitCode;    // the exit code of the process
 121     bool       state;         // set to FALSE when the process finishes
 122 };
 123
 124 #if defined(__WIN32__) && wxUSE_STREAMS
 125
 126 // ----------------------------------------------------------------------------
 127 // wxPipeStreams
 128 // ----------------------------------------------------------------------------
 129
 130 class wxPipeInputStream: public wxInputStream
 131 {
 132 public:
 133     wxPipeInputStream(HANDLE hInput);
 134     ~wxPipeInputStream();
 135
 136     virtual bool Eof() const;
 137
 138 protected:
 139     size_t OnSysRead(void *buffer, size_t len);
 140
 141 protected:
 142     HANDLE m_hInput;
 143 };
 144
 145 class wxPipeOutputStream: public wxOutputStream
 146 {
 147 public:
 148     wxPipeOutputStream(HANDLE hOutput);
 149     ~wxPipeOutputStream();
 150
 151 protected:
 152     size_t OnSysWrite(const void *buffer, size_t len);
 153
 154 protected:
 155     HANDLE m_hOutput;
 156 };
 157
 158 // ==================
 159 // wxPipeInputStream
 160 // ==================
 161
 162 wxPipeInputStream::wxPipeInputStream(HANDLE hInput)
 163 {
 164     m_hInput = hInput;
 165 }
 166
 167 wxPipeInputStream::~wxPipeInputStream()
 168 {
 169     ::CloseHandle(m_hInput);
 170 }
 171
 172 bool wxPipeInputStream::Eof() const
 173 {
 174     DWORD nAvailable;
 175
 176     // function name is misleading, it works with anon pipes as well
 177     DWORD rc = ::PeekNamedPipe
 178                     (
 179                       m_hInput,     // handle
 180                       NULL, 0,      // ptr to buffer and its size
 181                       NULL,         // [out] bytes read
 182                       &nAvailable,  // [out] bytes available
 183                       NULL          // [out] bytes left
 184                     );
 185
 186     if ( !rc )
 187     {
 188         if ( ::GetLastError() != ERROR_BROKEN_PIPE )
 189         {
 190             // unexpected error
 191             wxLogLastError(_T("PeekNamedPipe"));
 192         }
 193
 194         // don't try to continue reading from a pipe if an error occured or if
 195         // it had been closed
 196         return TRUE;
 197     }
 198     else
 199     {
 200         return nAvailable == 0;
 201     }
 202 }
 203
 204 size_t wxPipeInputStream::OnSysRead(void *buffer, size_t len)
 205 {
 206     // reading from a pipe may block if there is no more data, always check for
 207     // EOF first
 208     m_lasterror = wxSTREAM_NOERROR;
 209     if ( Eof() )
 210         return 0;
 211
 212     DWORD bytesRead;
 213     if ( !::ReadFile(m_hInput, buffer, len, &bytesRead, NULL) )
 214     {
 215         if ( ::GetLastError() == ERROR_BROKEN_PIPE )
 216             m_lasterror = wxSTREAM_EOF;
 217         else
 218             m_lasterror = wxSTREAM_READ_ERROR;
 219     }
 220
 221     return bytesRead;
 222 }
 223
 224 // ==================
 225 // wxPipeOutputStream
 226 // ==================
 227
 228 wxPipeOutputStream::wxPipeOutputStream(HANDLE hOutput)
 229 {
 230     m_hOutput = hOutput;
 231 }
 232
 233 wxPipeOutputStream::~wxPipeOutputStream()
 234 {
 235     ::CloseHandle(m_hOutput);
 236 }
 237
 238 size_t wxPipeOutputStream::OnSysWrite(const void *buffer, size_t len)
 239 {
 240     DWORD bytesRead;
 241
 242     m_lasterror = wxSTREAM_NOERROR;
 243     if ( !::WriteFile(m_hOutput, buffer, len, &bytesRead, NULL) )
 244     {
 245         if ( ::GetLastError() == ERROR_BROKEN_PIPE )
 246             m_lasterror = wxSTREAM_EOF;
 247         else
 248             m_lasterror = wxSTREAM_READ_ERROR;
 249     }
 250
 251     return bytesRead;
 252 }
 253
 254 #endif // __WIN32__
 255
 256 // ============================================================================
 257 // implementation
 258 // ============================================================================
 259
 260 #ifdef __WIN32__
 261
 262 static DWORD wxExecuteThread(wxExecuteData *data)
 263 {
 264     WaitForSingleObject(data->hProcess, INFINITE);
 265
 266     // get the exit code
 267     if ( !GetExitCodeProcess(data->hProcess, &data->dwExitCode) )
 268     {
 269         wxLogLastError(wxT("GetExitCodeProcess"));
 270     }
 271
 272     wxASSERT_MSG( data->dwExitCode != STILL_ACTIVE,
 273                   wxT("process should have terminated") );
 274
 275     // send a message indicating process termination to the window
 276     SendMessage(data->hWnd, wxWM_PROC_TERMINATED, 0, (LPARAM)data);
 277
 278     return 0;
 279 }
 280
 281 // window procedure of a hidden window which is created just to receive
 282 // the notification message when a process exits
 283 LRESULT APIENTRY _EXPORT wxExecuteWindowCbk(HWND hWnd, UINT message,
 284                                             WPARAM wParam, LPARAM lParam)
 285 {
 286     if ( message == wxWM_PROC_TERMINATED )
 287     {
 288         DestroyWindow(hWnd);    // we don't need it any more
 289
 290         wxExecuteData *data = (wxExecuteData *)lParam;
 291         if ( data->handler )
 292         {
 293             data->handler->OnTerminate((int)data->dwProcessId,
 294                                        (int)data->dwExitCode);
 295         }
 296
 297         if ( data->state )
 298         {
 299             // we're executing synchronously, tell the waiting thread
 300             // that the process finished
 301             data->state = 0;
 302         }
 303         else
 304         {
 305             // asynchronous execution - we should do the clean up
 306             delete data;
 307         }
 308
 309         return 0;
 310     }
 311     else
 312     {
 313         return DefWindowProc(hWnd, message, wParam, lParam);
 314     }
 315 }
 316 #endif // Win32
 317
 318 #if wxUSE_IPC
 319
 320 // connect to the given server via DDE and ask it to execute the command
 321 static bool wxExecuteDDE(const wxString& ddeServer,
 322                          const wxString& ddeTopic,
 323                          const wxString& ddeCommand)
 324 {
 325     bool ok;
 326
 327     wxDDEClient client;
 328     wxConnectionBase *conn = client.MakeConnection(_T(""),
 329                                                    ddeServer,
 330                                                    ddeTopic);
 331     if ( !conn )
 332     {
 333         ok = FALSE;
 334     }
 335     else // connected to DDE server
 336     {
 337         // the added complication here is that although most
 338         // programs use XTYP_EXECUTE for their DDE API, some
 339         // important ones - like IE and other MS stuff - use
 340         // XTYP_REQUEST!
 341         //
 342         // so we try it first and then the other one if it
 343         // failed
 344         {
 345             wxLogNull noErrors;
 346             ok = conn->Request(ddeCommand) != NULL;
 347         }
 348
 349         if ( !ok )
 350         {
 351             // now try execute - but show the errors
 352             ok = conn->Execute(ddeCommand);
 353         }
 354     }
 355
 356     return ok;
 357 }
 358
 359 #endif // wxUSE_IPC
 360
 361 long wxExecute(const wxString& cmd, bool sync, wxProcess *handler)
 362 {
 363     wxCHECK_MSG( !!cmd, 0, wxT("empty command in wxExecute") );
 364
 365     wxString command;
 366
 367 #if wxUSE_IPC
 368     // DDE hack: this is really not pretty, but we need to allow this for
 369     // transparent handling of DDE servers in wxMimeTypesManager. Usually it
 370     // returns the command which should be run to view/open/... a file of the
 371     // given type. Sometimes, however, this command just launches the server
 372     // and an additional DDE request must be made to really open the file. To
 373     // keep all this well hidden from the application, we allow a special form
 374     // of command: WX_DDE#<command>#DDE_SERVER#DDE_TOPIC#DDE_COMMAND in which
 375     // case we execute just <command> and process the rest below
 376     wxString ddeServer, ddeTopic, ddeCommand;
 377     static const size_t lenDdePrefix = 7;   // strlen("WX_DDE:")
 378     if ( cmd.Left(lenDdePrefix) == _T("WX_DDE#") )
 379     {
 380         // speed up the concatenations below
 381         ddeServer.reserve(256);
 382         ddeTopic.reserve(256);
 383         ddeCommand.reserve(256);
 384
 385         const wxChar *p = cmd.c_str() + 7;
 386         while ( *p && *p != _T('#') )
 387         {
 388             command += *p++;
 389         }
 390
 391         if ( *p )
 392         {
 393             // skip '#'
 394             p++;
 395         }
 396         else
 397         {
 398             wxFAIL_MSG(_T("invalid WX_DDE command in wxExecute"));
 399         }
 400
 401         while ( *p && *p != _T('#') )
 402         {
 403             ddeServer += *p++;
 404         }
 405
 406         if ( *p )
 407         {
 408             // skip '#'
 409             p++;
 410         }
 411         else
 412         {
 413             wxFAIL_MSG(_T("invalid WX_DDE command in wxExecute"));
 414         }
 415
 416         while ( *p && *p != _T('#') )
 417         {
 418             ddeTopic += *p++;
 419         }
 420
 421         if ( *p )
 422         {
 423             // skip '#'
 424             p++;
 425         }
 426         else
 427         {
 428             wxFAIL_MSG(_T("invalid WX_DDE command in wxExecute"));
 429         }
 430
 431         while ( *p )
 432         {
 433             ddeCommand += *p++;
 434         }
 435
 436         // if we want to just launch the program and not wait for its
 437         // termination, try to execute DDE command right now, it can succeed if
 438         // the process is already running - but as it fails if it's not
 439         // running, suppress any errors it might generate
 440         if ( !sync )
 441         {
 442             wxLogNull noErrors;
 443             if ( wxExecuteDDE(ddeServer, ddeTopic, ddeCommand) )
 444             {
 445                 // a dummy PID - this is a hack, of course, but it's well worth
 446                 // it as we don't open a new server each time we're called
 447                 // which would be quite bad
 448                 return -1;
 449             }
 450         }
 451     }
 452     else
 453 #endif // wxUSE_IPC
 454     {
 455         // no DDE
 456         command = cmd;
 457     }
 458
 459 #if defined(__WIN32__) && !defined(__TWIN32__)
 460
 461     // the IO redirection is only supported with wxUSE_STREAMS
 462     BOOL redirect = FALSE;
 463 #if wxUSE_STREAMS
 464     // the first elements are reading ends, the second are the writing ones
 465     HANDLE hpipeStdin[2],
 466            hpipeStdout[2],
 467            hpipeStderr[2];
 468     HANDLE hpipeStdinWrite = INVALID_HANDLE_VALUE;
 469
 470     // open the pipes to which child process IO will be redirected if needed
 471     if ( handler && handler->IsRedirected() )
 472     {
 473         // default secutiry attributes
 474         SECURITY_ATTRIBUTES security;
 475
 476         security.nLength              = sizeof(security);
 477         security.lpSecurityDescriptor = NULL;
 478         security.bInheritHandle       = TRUE;
 479
 480         // create stdin pipe
 481         if ( !::CreatePipe(&hpipeStdin[0], &hpipeStdin[1], &security, 0) )
 482         {
 483             wxLogSysError(_("Can't create the inter-process read pipe"));
 484
 485             // indicate failure in both cases
 486             return sync ? -1 : 0;
 487         }
 488
 489         // and a stdout one
 490         if ( !::CreatePipe(&hpipeStdout[0], &hpipeStdout[1], &security, 0) )
 491         {
 492             ::CloseHandle(hpipeStdin[0]);
 493             ::CloseHandle(hpipeStdin[1]);
 494
 495             wxLogSysError(_("Can't create the inter-process write pipe"));
 496
 497             return sync ? -1 : 0;
 498         }
 499
 500         (void)::CreatePipe(&hpipeStderr[0], &hpipeStderr[1], &security, 0);
 501
 502         redirect = TRUE;
 503     }
 504 #endif // wxUSE_STREAMS
 505
 506     // create the process
 507     STARTUPINFO si;
 508     wxZeroMemory(si);
 509     si.cb = sizeof(si);
 510
 511 #if wxUSE_STREAMS
 512     if ( redirect )
 513     {
 514         // when the std IO is redirected, we don't show the (console) process
 515         // window
 516         si.dwFlags = STARTF_USESTDHANDLES | STARTF_USESHOWWINDOW;
 517
 518         si.hStdInput = hpipeStdin[0];
 519         si.hStdOutput = hpipeStdout[1];
 520         si.hStdError = hpipeStderr[1];
 521
 522         si.wShowWindow = SW_HIDE;
 523
 524         // we must duplicate the handle to the write side of stdin pipe to make
 525         // it non inheritable: indeed, we must close hpipeStdin[1] before
 526         // launching the child process as otherwise this handle will be
 527         // inherited by the child which will never close it and so the pipe
 528         // will never be closed and the child will be left stuck in ReadFile()
 529         if ( !::DuplicateHandle
 530                 (
 531                     GetCurrentProcess(),
 532                     hpipeStdin[1],
 533                     GetCurrentProcess(),
 534                     &hpipeStdinWrite,
 535                     0,                      // desired access: unused here
 536                     FALSE,                  // not inherited
 537                     DUPLICATE_SAME_ACCESS   // same access as for src handle
 538                 ) )
 539         {
 540             wxLogLastError(_T("DuplicateHandle"));
 541         }
 542
 543         ::CloseHandle(hpipeStdin[1]);
 544     }
 545 #endif // wxUSE_STREAMS
 546
 547     PROCESS_INFORMATION pi;
 548     DWORD dwFlags = CREATE_DEFAULT_ERROR_MODE | CREATE_SUSPENDED;
 549
 550     bool ok = ::CreateProcess
 551                 (
 552                  NULL,              // application name (use only cmd line)
 553                  (wxChar *)
 554                  command.c_str(),   // full command line
 555                  NULL,              // security attributes: defaults for both
 556                  NULL,              //   the process and its main thread
 557                  redirect,          // inherit handles if we use pipes
 558                  dwFlags,           // process creation flags
 559                  NULL,              // environment (use the same)
 560                  NULL,              // current directory (use the same)
 561                  &si,               // startup info (unused here)
 562                  &pi                // process info
 563                 ) != 0;
 564
 565 #if wxUSE_STREAMS
 566     // we can close the pipe ends used by child anyhow
 567     if ( redirect )
 568     {
 569         ::CloseHandle(hpipeStdin[0]);
 570         ::CloseHandle(hpipeStdout[1]);
 571         ::CloseHandle(hpipeStderr[1]);
 572     }
 573 #endif // wxUSE_STREAMS
 574
 575     if ( !ok )
 576     {
 577 #if wxUSE_STREAMS
 578         // close the other handles too
 579         if ( redirect )
 580         {
 581             ::CloseHandle(hpipeStdout[0]);
 582             ::CloseHandle(hpipeStderr[0]);
 583         }
 584 #endif // wxUSE_STREAMS
 585
 586         wxLogSysError(_("Execution of command '%s' failed"), command.c_str());
 587
 588         return sync ? -1 : 0;
 589     }
 590
 591 #if wxUSE_STREAMS
 592     if ( redirect )
 593     {
 594         // We can now initialize the wxStreams
 595         wxInputStream *inStream = new wxPipeInputStream(hpipeStdout[0]),
 596                       *errStream = new wxPipeInputStream(hpipeStderr[0]);
 597         wxOutputStream *outStream = new wxPipeOutputStream(hpipeStdinWrite);
 598
 599         handler->SetPipeStreams(inStream, outStream, errStream);
 600     }
 601 #endif // wxUSE_STREAMS
 602
 603     // register the class for the hidden window used for the notifications
 604     if ( !gs_classForHiddenWindow )
 605     {
 606         gs_classForHiddenWindow = _T("wxHiddenWindow");
 607
 608         WNDCLASS wndclass;
 609         wxZeroMemory(wndclass);
 610         wndclass.lpfnWndProc   = (WNDPROC)wxExecuteWindowCbk;
 611         wndclass.hInstance     = wxGetInstance();
 612         wndclass.lpszClassName = gs_classForHiddenWindow;
 613
 614         if ( !::RegisterClass(&wndclass) )
 615         {
 616             wxLogLastError(wxT("RegisterClass(hidden window)"));
 617         }
 618     }
 619
 620     // create a hidden window to receive notification about process
 621     // termination
 622     HWND hwnd = ::CreateWindow(gs_classForHiddenWindow, NULL,
 623                                WS_OVERLAPPEDWINDOW,
 624                                0, 0, 0, 0, NULL,
 625                                (HMENU)NULL, wxGetInstance(), 0);
 626     wxASSERT_MSG( hwnd, wxT("can't create a hidden window for wxExecute") );
 627
 628     // Alloc data
 629     wxExecuteData *data = new wxExecuteData;
 630     data->hProcess    = pi.hProcess;
 631     data->dwProcessId = pi.dwProcessId;
 632     data->hWnd        = hwnd;
 633     data->state       = sync;
 634     if ( sync )
 635     {
 636         // handler may be !NULL for capturing program output, but we don't use
 637         // it wxExecuteData struct in this case
 638         data->handler = NULL;
 639     }
 640     else
 641     {
 642         // may be NULL or not
 643         data->handler = handler;
 644     }
 645
 646     DWORD tid;
 647     HANDLE hThread = ::CreateThread(NULL,
 648                                     0,
 649                                     (LPTHREAD_START_ROUTINE)wxExecuteThread,
 650                                     (void *)data,
 651                                     0,
 652                                     &tid);
 653
 654     // resume process we created now - whether the thread creation succeeded or
 655     // not
 656     if ( ::ResumeThread(pi.hThread) == (DWORD)-1 )
 657     {
 658         // ignore it - what can we do?
 659         wxLogLastError(wxT("ResumeThread in wxExecute"));
 660     }
 661
 662     // close unneeded handle
 663     if ( !::CloseHandle(pi.hThread) )
 664         wxLogLastError(wxT("CloseHandle(hThread)"));
 665
 666     if ( !hThread )
 667     {
 668         wxLogLastError(wxT("CreateThread in wxExecute"));
 669
 670         DestroyWindow(hwnd);
 671         delete data;
 672
 673         // the process still started up successfully...
 674         return pi.dwProcessId;
 675     }
 676
 677     ::CloseHandle(hThread);
 678
 679 #if wxUSE_IPC
 680     // second part of DDE hack: now establish the DDE conversation with the
 681     // just launched process
 682     if ( !ddeServer.empty() )
 683     {
 684         bool ok;
 685
 686         // give the process the time to init itself
 687         //
 688         // we use a very big timeout hoping that WaitForInputIdle() will return
 689         // much sooner, but not INFINITE just in case the process hangs
 690         // completely - like this we will regain control sooner or later
 691         switch ( ::WaitForInputIdle(pi.hProcess, 10000 /* 10 seconds */) )
 692         {
 693             default:
 694                 wxFAIL_MSG( _T("unexpected WaitForInputIdle() return code") );
 695                 // fall through
 696
 697             case -1:
 698                 wxLogLastError(_T("WaitForInputIdle() in wxExecute"));
 699
 700             case WAIT_TIMEOUT:
 701                 wxLogDebug(_T("Timeout too small in WaitForInputIdle"));
 702
 703                 ok = FALSE;
 704                 break;
 705
 706             case 0:
 707                 // ok, process ready to accept DDE requests
 708                 ok = wxExecuteDDE(ddeServer, ddeTopic, ddeCommand);
 709         }
 710     }
 711 #endif // wxUSE_IPC
 712
 713     if ( !sync )
 714     {
 715         // clean up will be done when the process terminates
 716
 717         // return the pid
 718         return pi.dwProcessId;
 719     }
 720
 721     // waiting until command executed (disable everything while doing it)
 722 #if wxUSE_GUI
 723     {
 724         wxBusyCursor bc;
 725
 726         wxWindowDisabler wd;
 727 #endif // wxUSE_GUI
 728
 729     while ( data->state )
 730         wxYield();
 731
 732 #if wxUSE_GUI
 733     }
 734 #endif // wxUSE_GUI
 735
 736     DWORD dwExitCode = data->dwExitCode;
 737     delete data;
 738
 739     // return the exit code
 740     return dwExitCode;
 741 #else // Win16
 742     long instanceID = WinExec((LPCSTR) WXSTRINGCAST command, SW_SHOW);
 743     if (instanceID < 32) return(0);
 744
 745     if (sync) {
 746         int running;
 747         do {
 748             wxYield();
 749             running = GetModuleUsage((HINSTANCE)instanceID);
 750         } while (running);
 751     }
 752
 753     return(instanceID);
 754 #endif // Win16/32
 755 }
 756
 757 long wxExecute(char **argv, bool sync, wxProcess *handler)
 758 {
 759     wxString command;
 760
 761     while ( *argv != NULL )
 762     {
 763         command << *argv++ << ' ';
 764     }
 765
 766     command.RemoveLast();
 767
 768     return wxExecute(command, sync, handler);
 769 }
 770