docs/latex/wx/snglinst.tex

   1 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
   2 %% Name:        snglinst.tex
   3 %% Purpose:     wxSingleInstanceChecker documentation
   4 %% Author:      Vadim Zeitlin
   5 %% Modified by:
   6 %% Created:     08.06.01
   7 %% RCS-ID:      $Id$
   8 %% Copyright:   (c) 2001 Vadim Zeitlin
   9 %% License:     wxWindows license
  10 %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%
  11
  12 \section{\class{wxSingleInstanceChecker}}\label{wxsingleinstancechecker}
  13
  14 wxSingleInstanceChecker class allows to check that only a single instance of a
  15 program is running. To do it, you should create an object of this class. As
  16 long as this object is alive, calls to
  17 \helpref{IsAnotherRunning()}{wxsingleinstancecheckerisanotherrunning} from
  18 other processes will return {\tt true}.
  19
  20 As the object should have the life span as big as possible, it makes sense to
  21 create it either as a global or in \helpref{wxApp::OnInit}{wxapponinit}. For
  22 example:
  23
  24 \begin{verbatim}
  25 bool MyApp::OnInit()
  26 {
  27     const wxString name = wxString::Format("MyApp-%s", wxGetUserId().c_str());
  28     m_checker = new wxSingleInstanceChecker(name);
  29     if ( m_checker->IsAnotherRunning() )
  30     {
  31         wxLogError(_("Another program instance is already running, aborting."));
  32
  33         delete m_checker; // OnExit() won't be called if we return false
  34         m_checker = NULL;
  35
  36         return false;
  37     }
  38
  39     ... more initializations ...
  40
  41     return true;
  42 }
  43
  44 int MyApp::OnExit()
  45 {
  46     delete m_checker;
  47
  48     return 0;
  49 }
  50 \end{verbatim}
  51
  52 Note using \helpref{wxGetUserId()}{wxgetuserid} to construct the name: this
  53 allows different user to run the application concurrently which is usually the
  54 intended goal. If you don't use the user name in the wxSingleInstanceChecker
  55 name, only one user would be able to run the application at a time.
  56
  57 This class is implemented for Win32 and Unix platforms (supporting {\tt fcntl()}
  58 system call, but almost all of modern Unix systems do) only.
  59
  60 \wxheading{Derived from}
  61
  62 No base class
  63
  64 \wxheading{Include files}
  65
  66 <wx/snglinst.h>
  67
  68 \wxheading{Library}
  69
  70 \helpref{wxBase}{librarieslist}
  71
  72 \latexignore{\rtfignore{\wxheading{Members}}}
  73
  74 \membersection{wxSingleInstanceChecker::wxSingleInstanceChecker}\label{wxsingleinstancecheckerctor}
  75
  76 \func{}{wxSingleInstanceChecker}{\void}
  77
  78 Default ctor, use \helpref{Create()}{wxsingleinstancecheckercreate} after it.
  79
  80 \membersection{wxSingleInstanceChecker::wxSingleInstanceChecker}\label{wxsingleinstancecheckerwxsingleinstancechecker}
  81
  82 \func{}{wxSingleInstanceChecker}{\param{const wxString\& }{name}, \param{const wxString\& }{path = wxEmptyString}}
  83
  84 Like \helpref{Create()}{wxsingleinstancecheckercreate} but without
  85 error checking.
  86
  87 \membersection{wxSingleInstanceChecker::Create}\label{wxsingleinstancecheckercreate}
  88
  89 \func{bool}{Create}{\param{const wxString\& }{name}, \param{const wxString\& }{path = wxEmptyString}}
  90
  91 Initialize the object if it had been created using the default constructor.
  92 Note that you can't call Create() more than once, so calling it if the
  93 \helpref{non default ctor}{wxsingleinstancecheckerwxsingleinstancechecker}
  94 had been used is an error.
  95
  96 \wxheading{Parameters}
  97
  98 \docparam{name}{must be given and be as unique as possible. It is used as the
  99 mutex name under Win32 and the lock file name under Unix.
 100 \helpref{GetAppName()}{wxappgetappname} and \helpref{wxGetUserId()}{wxgetuserid}
 101 are commonly used to construct this parameter.}
 102
 103 \docparam{path}{is optional and is ignored under Win32 and used as the directory to
 104 create the lock file in under Unix (default is
 105 \helpref{wxGetHomeDir()}{wxgethomedir})}
 106
 107 \wxheading{Return value}
 108
 109 Returns {\tt false} if initialization failed, it doesn't mean that another
 110 instance is running - use
 111 \helpref{IsAnotherRunning()}{wxsingleinstancecheckerisanotherrunning} to check
 112 for it.
 113
 114 \wxheading{Note}
 115
 116 One of possible reasons while Create may fail on Unix is that the lock file
 117 used for checking already exists but was not created by the user.
 118 Therefore applications shouldn't treat failure of this function as fatal
 119 condition, because doing so would open them to the possibility of a Denial of
 120 Service attack. Instead, they should alert the user about the problem and
 121 offer to continue execution without checking if another instance is running.
 122
 123 \membersection{wxSingleInstanceChecker::IsAnotherRunning}\label{wxsingleinstancecheckerisanotherrunning}
 124
 125 \constfunc{bool}{IsAnotherRunning}{\void}
 126
 127 Returns {\tt true} if another copy of this program is already running, {\tt
 128 false} otherwise.
 129
 130 \membersection{wxSingleInstanceChecker::\destruct{wxSingleInstanceChecker}}\label{wxsingleinstancecheckerdtor}
 131
 132 \func{}{\destruct{wxSingleInstanceChecker}}{\void}
 133
 134 Destructor frees the associated resources.
 135
 136 Note that it is not virtual, this class is not meant to be used polymorphically
 137