Here’s another little “gotcha” from my experimentations in running C# apps cross-platform. The following code implements a system-wide mutex to ensure that only one instance of the program is running at any one time:<\/p>\n
\r\npublic static void Main(string[] args){\r\n\tMutex mutex = null;\r\n\ttry{\r\n\t\tmutex = Mutex.OpenExisting("test.martyndavis.com");\r\n\t\t\/\/ if we *can* open it we're an ADDITIONAL instance\r\n\t\tConsole.WriteLine("Application is already running");\r\n\t\treturn;\r\n\t} catch(WaitHandleCannotBeOpenedException){\r\n\t\t\/\/ if we get in here then the mutex doesn't exist,\r\n\t\t\/\/ so we are the only instance running on this machine\r\n mutex = new System.Threading.Mutex(true, "test.martyndavis.com");\r\n\t}\r\n\ttry{\r\n\t\tConsole.WriteLine("Doing stuff... press a key");\r\n Console.Read();\r\n\t} finally{\r\n\t\t\/\/ Although mutex implements IDisposable, it doesn't\r\n\t\t\/\/ call Release Mutex when being Disposed(),\r\n\t\t\/\/ hence usage of try\/finally instead of 'using'.\r\n\t\tmutex.ReleaseMutex();\r\n\t}\r\n}\r\n<\/pre>\nRunning this on Windows it behaves as one would expect. Run one instance you get “Doing stuff… press a key” output, and, if you try to run a second instance in another DOS box you get “Application is already running”.<\/p>\n
On Linux though it’s a different story – each instance runs as if it’s the only copy on the machine.<\/p>\n