program is running. To do it, you should create an object of this class. As
long as this object is alive, calls to
\helpref{IsAnotherRunning()}{wxsingleinstancecheckerisanotherrunning} from
-other processes will return {\tt TRUE}.
+other processes will return {\tt true}.
As the object should have the life span as big as possible, it makes sense to
create it either as a global or in \helpref{wxApp::OnInit}{wxapponinit}. For
\begin{verbatim}
bool MyApp::OnInit()
{
- m_checker = new wxSingleInstanceChecker(GetAppName());
+ const wxString name = wxString::Format("MyApp-%s", wxGetUserId().c_str());
+ m_checker = new wxSingleInstanceChecker(name);
if ( m_checker->IsAnotherRunning() )
{
wxLogError(_("Another program instance is already running, aborting."));
- return FALSE;
+ delete m_checker; // OnExit() won't be called if we return false
+ m_checker = NULL;
+
+ return false;
}
... more initializations ...
- return TRUE;
+ return true;
}
int MyApp::OnExit()
}
\end{verbatim}
-This class is implemented for Win32 and Unix platforms supporting {\tt fcntl()}
-system call only.
+Note using \helpref{wxGetUserId()}{wxgetuserid} to construct the name: this
+allows different user to run the application concurrently which is usually the
+intended goal. If you don't use the user name in the wxSingleInstanceChecker
+name, only one user would be able to run the application at a time.
+
+This class is implemented for Win32 and Unix platforms (supporting {\tt fcntl()}
+system call, but almost all of modern Unix systems do) only.
\wxheading{Derived from}
No base class
-\wxheading{Data structures}
+\wxheading{Include files}
+
+<wx/snglinst.h>
+
+\wxheading{Library}
+
+\helpref{wxBase}{librarieslist}
\latexignore{\rtfignore{\wxheading{Members}}}
\wxheading{Parameters}
-\docparam{name}{must be given and be as unique as possible, it is used as the
+\docparam{name}{must be given and be as unique as possible. It is used as the
mutex name under Win32 and the lock file name under Unix.
-\helpref{GetAppName()}{wxappgetappname} may be a good value for this parameter}
+\helpref{GetAppName()}{wxappgetappname} and \helpref{wxGetUserId()}{wxgetuserid}
+are commonly used to construct this parameter.}
\docparam{path}{is optional and is ignored under Win32 and used as the directory to
create the lock file in under Unix (default is
\wxheading{Return value}
-Returns {\tt FALSE} if initialization failed, it doesn't mean that another
+Returns {\tt false} if initialization failed, it doesn't mean that another
instance is running - use
\helpref{IsAnotherRunning()}{wxsingleinstancecheckerisanotherrunning} to check
for it.
+\wxheading{Note}
+
+One of possible reasons while Create may fail on Unix is that the lock file
+used for checking already exists but was not created by the user.
+Therefore applications shouldn't treat failure of this function as fatal
+condition, because doing so would open them to the possibility of a Denial of
+Service attack. Instead, they should alert the user about the problem and
+offer to continue execution without checking if another instance is running.
+
\membersection{wxSingleInstanceChecker::IsAnotherRunning}\label{wxsingleinstancecheckerisanotherrunning}
\constfunc{bool}{IsAnotherRunning}{\void}
-Returns {\tt TRUE} if another copy of this program is already running, {\tt
-FALSE} otherwise.
+Returns {\tt true} if another copy of this program is already running, {\tt
+false} otherwise.
\membersection{wxSingleInstanceChecker::\destruct{wxSingleInstanceChecker}}\label{wxsingleinstancecheckerdtor}