@class wxSingleInstanceChecker
wxSingleInstanceChecker class allows to check that only a single instance of a
- program is running. To do it, you should create an object of this class. As
- long as this object is alive, calls to
- wxSingleInstanceChecker::IsAnotherRunning from
- other processes will return @true.
+ program is running.
+
+ To do it, you should create an object of this class. As long as this object
+ is alive, calls to wxSingleInstanceChecker::IsAnotherRunning from other
+ processes will return @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 wxApp::OnInit. For
- example:
+ create it either as a global or in wxApp::OnInit.
+ For example:
@code
bool MyApp::OnInit()
}
@endcode
- Note using 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.
+ Note using 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 @c fcntl()
system call, but almost all of modern Unix systems do) only.
{
public:
/**
- Like Create() but without
- error checking.
+ Default ctor, use Create() after it.
+ */
+ wxSingleInstanceChecker();
+
+ /**
+ Like Create() but without error checking.
*/
wxSingleInstanceChecker(const wxString& name,
const wxString& path = wxEmptyString);
/**
Destructor frees the associated resources.
- Note that it is not virtual, this class is not meant to be used polymorphically
+ Note that it is not virtual, this class is not meant to be used polymorphically.
*/
~wxSingleInstanceChecker();
/**
Initialize the object if it had been created using the default constructor.
Note that you can't call Create() more than once, so calling it if the
- @ref wxsingleinstancechecker() "non default ctor"
- had been used is an error.
+ @ref wxSingleInstanceChecker() "non default ctor" had been used is an error.
@param name
- must be given and be as unique as possible. It is used as the
+ 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.
- GetAppName() and wxGetUserId()
- are commonly used to construct this parameter.
+ GetAppName() and wxGetUserId() are commonly used to construct
+ this parameter.
@param path
- is optional and is ignored under Win32 and used as the directory to
- create the lock file in under Unix (default is
- wxGetHomeDir())
+ The path is optional and is ignored under Win32 and used as the
+ directory to create the lock file in under Unix
+ (default is wxGetHomeDir()).
@return Returns @false if initialization failed, it doesn't mean that
- another instance is running - use IsAnotherRunning()
- to check for it.
+ another instance is running - use IsAnotherRunning() to check
+ for it.
+
+ @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.
*/
bool Create(const wxString& name,
const wxString& path = wxEmptyString);