Delphi.IsSingleInstance

Проверка “а один ли экземпляр запущен ?”. Работает в мультипользовательском режиме, в отличие от “обычного” мьютекса.

//Creates a mutex to see if the program is already running.
function IsSingleInstance(MutexName: string; KeepMutex: boolean = true): boolean;
const
  MUTEX_GLOBAL = 'Global\'; //Prefix to explicitly create the object in the global or session namespace. I.e. both client app (local user) and service (system account)
var
  MutexHandel: THandle;
  SecurityDesc: TSecurityDescriptor;
  SecurityAttr: TSecurityAttributes;
  ErrCode: integer;
begin
    // By default (lpMutexAttributes =nil) created mutexes are accessible only by
    // the user running the process. We need our mutexes to be accessible to all
    // users, so that the mutex detection can work across user sessions.
    // I.e. both the current user account and the System (Service) account.
    // To do this we use a security descriptor with a null DACL.
  InitializeSecurityDescriptor(@SecurityDesc, SECURITY_DESCRIPTOR_REVISION);
  SetSecurityDescriptorDacl(@SecurityDesc, True, nil, False);
  SecurityAttr.nLength := SizeOf(SecurityAttr);
  SecurityAttr.lpSecurityDescriptor := @SecurityDesc;
  SecurityAttr.bInheritHandle := False;

    // The mutex is created in the global name space which makes it possible to
    // access across user sessions.
  MutexHandel := CreateMutex(@SecurityAttr, True, PChar(MUTEX_GLOBAL + MutexName));
  ErrCode := GetLastError;

    // If the function fails, the return value is 0
    // If the mutex is a named mutex and the object existed before this function
    // call, the return value is a handle to the existing object, GetLastError
    // returns ERROR_ALREADY_EXISTS.
  if {(MutexHandel = 0) or } (ErrCode = ERROR_ALREADY_EXISTS) then
  begin
    result := false;
    closeHandle(MutexHandel);
  end
  else
  begin
    // Mutex object has not yet been created, meaning that no previous
    // instance has been created.
    result := true;

    if not KeepMutex then
      CloseHandle(MutexHandel);
  end;
    // The Mutexhandle is not closed because we want it to exist during the
    // lifetime of the application. The system closes the handle automatically
    //when the process terminates.
end;

//Creates a mutex to see if the program is already running.

function IsSingleInstance(MutexName: string; KeepMutex: boolean = true): boolean;

const

MUTEX_GLOBAL = 'Global\'; //Prefix to explicitly create the object in the global or session namespace. I.e. both client app (local user) and service (system account)

var

MutexHandel: THandle;

SecurityDesc: TSecurityDescriptor;

SecurityAttr: TSecurityAttributes;

ErrCode: integer;

begin

// By default (lpMutexAttributes =nil) created mutexes are accessible only by

// the user running the process. We need our mutexes to be accessible to all

// users, so that the mutex detection can work across user sessions.

// I.e. both the current user account and the System (Service) account.

// To do this we use a security descriptor with a null DACL.

InitializeSecurityDescriptor(@SecurityDesc, SECURITY_DESCRIPTOR_REVISION);

SetSecurityDescriptorDacl(@SecurityDesc, True, nil, False);

SecurityAttr.nLength := SizeOf(SecurityAttr);

SecurityAttr.lpSecurityDescriptor := @SecurityDesc;

SecurityAttr.bInheritHandle := False;

// The mutex is created in the global name space which makes it possible to

// access across user sessions.

MutexHandel := CreateMutex(@SecurityAttr, True, PChar(MUTEX_GLOBAL + MutexName));

ErrCode := GetLastError;

// If the function fails, the return value is 0

// If the mutex is a named mutex and the object existed before this function

// call, the return value is a handle to the existing object, GetLastError

// returns ERROR_ALREADY_EXISTS.

if {(MutexHandel = 0) or } (ErrCode = ERROR_ALREADY_EXISTS) then

begin

result := false;

closeHandle(MutexHandel);

end

else

begin

// Mutex object has not yet been created, meaning that no previous

// instance has been created.

result := true;

if not KeepMutex then

CloseHandle(MutexHandel);

end;

// The Mutexhandle is not closed because we want it to exist during the

// lifetime of the application. The system closes the handle automatically

//when the process terminates.

end;

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