BorlandTalk.com Borland discussion newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Only One Instance. Goto page 1, 2  Next          BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.misc View previous topic :: View next topic   Author Message John Dammeyer Guest Posted: Wed Jan 14, 2004 5:07 pm    Post subject: Only One Instance. Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. Thanks, John Back to top Dave Guest Posted: Wed Jan 14, 2004 5:45 pm    Post subject: Re: Only One Instance. "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. This is what I use. Not my code...I think I got it from someone in this group quite a while back, but it works like a charm: //Prevent multiple instances of the program from running StrPCopy(MutexName, 'anyname'); Mutex := OpenMutex(MUTEX_ALL_ACCESS, False, MutexName); If Mutex <> 0 then begin Exit; end; Mutex := CreateMutex(nil , True, MutexName); ReleaseMutex(Mutex); - Dave Back to top Rob Kennedy Guest Posted: Wed Jan 14, 2004 6:17 pm    Post subject: Re: Only One Instance. John Dammeyer wrote: Quote: Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. You can? As I understand it, as of 1995, that parameter will always be zero. Win32 doesn't have instance handles anymore. You can use the HPrevInst variable in Delphi, which is initialized the same way WinMain's parameter is. It won't be of any use, though. Quote: How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. Have you searched the newsgroups? When using CreateMutex, please read the documentation carefully regarding choosing a name. The naming rules vary by OS version, and some names have a wider scope than others. -- Rob Back to top Maarten Wiltink Guest Posted: Wed Jan 14, 2004 7:19 pm    Post subject: Re: Only One Instance. "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. http://www.bancoems.com/CompLangPascalDelphiMisc-MiniFAQ.htm Question two. Groetjes, Maarten Wiltink Back to top Leonardo Cardoso Monteiro Guest Posted: Wed Jan 14, 2004 8:22 pm    Post subject: Re: Only One Instance. "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. Thanks, John From MS documentation: hPrevInstance [in] Handle to the previous instance of the application. This parameter is always NULL. If you need to detect whether another instance already exists, create a uniquely named mutex using the CreateMutex function. CreateMutex will succeed even if the mutex already exists, but the function will return ERROR_ALREADY_EXISTS. This indicates that another instance of your application exists, because it created the mutex first. Leonardo Back to top Rob Kennedy Guest Posted: Wed Jan 14, 2004 9:09 pm    Post subject: Re: Only One Instance. Jamie wrote: Quote: i always found that if you can only have one instance of the app then you should Special Name the Main Form Class to something that should never exist, use the FINDWIndow in the Main Source before The TAPplication.initiate gets executed.. Or, you could simply create a mutex. Advantages: 1. The name of the mutex has no effect on anything else in your program, so you can continue to name your objects however you want. 2. The mutex name is more likely to be unique within the system. You can even use a GUID. 3. Mutex creation is atomic. It is impossible for two processes to create like-named mutexes without knowing it. Creating a window, on the other hand, is not atomic. If process A and process B are started simultaneously, they might both call FindWindow before either one has created the window that the other process is looking for. Quote: if you find the CLASS then you should use the SENDMESSAGE to that handle that you have receieved with a special user message that you have your app responed to .. if all of this falls into play then you can be as sured that you have a copy of your app running. But there is no guarantee that any of that will fall into place. When your main form is open in the IDE, it has the same class name and title as the form your program creates. FindWindow might find that window, which makes testing and debugging inconvenient. FindWindow is an attractive function because it's easy to use and it's easy for novices to understand. But it's simply not the right tool for the job. Quote: there the methods that others use like CreateMutex etc.. but i found that if the SENDMESSAGE works your app can return back aditional info that you may want also to insure its your app and not just some fluke that there is another app on the desktop running that way.,.. Using a mutex does not preclude usage of other techniques for transferring control to the previous instance. However, a mutex is a guaranteed method of detecting multiple instances. FindWindow offers absolutely no guarantees. Besides, if the window you find doesn't return the value you were expecting, then you've determined that you didn't find the right window. But now what? You still can't conclude that no other instances of your program are running. FindWindow only returns one window, and it always returns the first one it finds. If you want to communicate with the existing instance of a program, then you can use a mailslot instead of a mutex. Like mutex names, mailslot names are unique on a system, so you can use CreateMailslot just as you would use CreateMutex. Mailslots also allow you to send information to the first instance, so the first instance can receive subsequent instances' command-line parameters. -- Rob Back to top John Dammeyer Guest Posted: Wed Jan 14, 2004 10:15 pm    Post subject: Re: Only One Instance. "Leonardo Cardoso Monteiro" <cardoso (AT) iis (DOT) com.br> wrote: Hi, Thanks. Shows how dated I am on Windows Programming for some things. My target is a WIN98SE system. I'll check out the MUTEX stuff. Thanks, John Quote: From MS documentation: hPrevInstance [in] Handle to the previous instance of the application. This parameter is always NULL. If you need to detect whether another instance already exists, create a uniquely named mutex using the CreateMutex function. CreateMutex will succeed even if the mutex already exists, but the function will return ERROR_ALREADY_EXISTS. This indicates that another instance of your application exists, because it created the mutex first. Leonardo Back to top John Dammeyer Guest Posted: Wed Jan 14, 2004 10:32 pm    Post subject: Re: Only One Instance. dank ja wel, This worked perfect. With a running instance I can click on the .exe file over and over again and it never starts a second one. John "Maarten Wiltink" <maarten (AT) kittensandcats (DOT) net> wrote: Quote: "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote in message news:40057530.3496597 (AT) news (DOT) islandnet.com... Hi All, My application needs to run on program startup. <snip> Quote: How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. http://www.bancoems.com/CompLangPascalDelphiMisc-MiniFAQ.htm Question two. Groetjes, Maarten Wiltink Back to top Jamie Guest Posted: Wed Jan 14, 2004 11:08 pm    Post subject: Re: Only One Instance. i always found that if you can only have one instance of the app then you should Special Name the Main Form Class to something that should never exist, use the FINDWIndow in the Main Source before The TAPplication.initiate gets executed.. if you find the CLASS then you should use the SENDMESSAGE to that handle that you have receieved with a special user message that you have your app responed to .. if all of this falls into play then you can be as sured that you have a copy of your app running. there the methods that others use like CreateMutex etc.. but i found that if the SENDMESSAGE works your app can return back aditional info that you may want also to insure its your app and not just some fluke that there is another app on the desktop running that way.,.. John Dammeyer wrote: Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. Thanks, John Back to top J French Guest Posted: Thu Jan 15, 2004 8:24 am    Post subject: Re: Only One Instance. On Wed, 14 Jan 2004 17:07:34 GMT, [email]johnd (AT) STRIP (DOT) autoartisans.com[/email] (John Dammeyer) wrote: Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. <snip> Apart from Mutexes, RegisterWindowsMessage is handy for this sort of thing Back to top Jamie Guest Posted: Thu Jan 15, 2004 10:08 am    Post subject: Re: Only One Instance. well what ever, i have used AToms, Mutexes, MemoryFile and FindWIndow with post backs. i can tell you that for me using custom name Main Window Classes per APP not the default "TFORM1" that every one uses with post back helps me grately. because it also is able to return back to the secondary app the handle info of the original app along with what ever else i need for it at the time. this way i can pop the original to the front and then exist the secondary etc.. i am sure that your way works well for what you do, i have extra requirements on some of the code i write. I also had to use EnumWindows, get the Handle, use PostBack function to get the start up times and other initiated info per instant. so that the current instant coming up would be inline with the others.. so what ever., i guess what ever way works for it is what you use.. Rob Kennedy wrote: Quote: Jamie wrote: i always found that if you can only have one instance of the app then you should Special Name the Main Form Class to something that should never exist, use the FINDWIndow in the Main Source before The TAPplication.initiate gets executed.. Or, you could simply create a mutex. Advantages: 1. The name of the mutex has no effect on anything else in your program, so you can continue to name your objects however you want. 2. The mutex name is more likely to be unique within the system. You can even use a GUID. 3. Mutex creation is atomic. It is impossible for two processes to create like-named mutexes without knowing it. Creating a window, on the other hand, is not atomic. If process A and process B are started simultaneously, they might both call FindWindow before either one has created the window that the other process is looking for. if you find the CLASS then you should use the SENDMESSAGE to that handle that you have receieved with a special user message that you have your app responed to .. if all of this falls into play then you can be as sured that you have a copy of your app running. But there is no guarantee that any of that will fall into place. When your main form is open in the IDE, it has the same class name and title as the form your program creates. FindWindow might find that window, which makes testing and debugging inconvenient. FindWindow is an attractive function because it's easy to use and it's easy for novices to understand. But it's simply not the right tool for the job. there the methods that others use like CreateMutex etc.. but i found that if the SENDMESSAGE works your app can return back aditional info that you may want also to insure its your app and not just some fluke that there is another app on the desktop running that way.,.. Using a mutex does not preclude usage of other techniques for transferring control to the previous instance. However, a mutex is a guaranteed method of detecting multiple instances. FindWindow offers absolutely no guarantees. Besides, if the window you find doesn't return the value you were expecting, then you've determined that you didn't find the right window. But now what? You still can't conclude that no other instances of your program are running. FindWindow only returns one window, and it always returns the first one it finds. If you want to communicate with the existing instance of a program, then you can use a mailslot instead of a mutex. Like mutex names, mailslot names are unique on a system, so you can use CreateMailslot just as you would use CreateMutex. Mailslots also allow you to send information to the first instance, so the first instance can receive subsequent instances' command-line parameters. Back to top Bruce Roberts Guest Posted: Thu Jan 15, 2004 3:29 pm    Post subject: Re: Only One Instance. "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote Quote: This worked perfect. With a running instance I can click on the .exe file over and over again and it never starts a second one. Actually a second instance is started every time. It just exits before doing anything significant. Back to top Maarten Wiltink Guest Posted: Thu Jan 15, 2004 7:46 pm    Post subject: Re: Only One Instance. "Bruce Roberts" <ber (AT) bounceitattcanada (DOT) xnet> wrote Quote: "John Dammeyer" <johnd (AT) STRIP (DOT) autoartisans.com> wrote in message news:4005c2e7.23391004 (AT) news (DOT) islandnet.com... <miniFAQ> Quote: This worked perfect. With a running instance I can click on the .exe file over and over again and it never starts a second one. Actually a second instance is started every time. It just exits before doing anything significant. If it could insignificantly bring the previous instance to the foreground, I would consider that significant and quite useful. I don't know if you can still do that, though. Didn't the behaviour change some time ago to merely flashing the taskbar button rather than grabbing the focus? Groetjes, Maarten Wiltink Back to top Ian Robinson Guest Posted: Fri Jan 16, 2004 10:53 am    Post subject: Re: Only One Instance. I use this... function DoIExist: Boolean; var hSem: THandle; begin //Create a Semaphore in memory - If this is the first instance, then //it should be 0. hSem := CreateSemaphore (nil, 0, 1, PChar ('Nainosnibor')); Result := GetLastError = ERROR_ALREADY_EXISTS; if Result then CloseHandle (hSem); end; In message <40057530.3496597 (AT) news (DOT) islandnet.com>, John Dammeyer <johnd (AT) STRIP (DOT) autoartisans.com> said Quote: Hi All, My application needs to run on program startup. I've had it working well with an entry into the registry but during development I made a few errors and ended up with two app.exe entries in the registry. I can't ever have more than one instance running due to hardware accesses. Remoing the multiple entries was not a big problem to handle with regedit.exe but in C I can check hPrevInstance to see if there is already something running. e.g. int APIENTRY WinMain(HINSTANCE hInstance,HINSTANCE hPrevInstance,LPSTR lpCmdLine, And then exit out if hPrevInstance was non zero. How do I do this in Delphi 5? I've searched the Forms and System files but can't find anything specific. Thanks, John -- Best regards Ian Robinson FOREST SOFTWARE +44(0)1594 564457 (Office) +44(0)7718 806 006 (UK Mobile) +34 653 209 592 (Overseas Mobile) +44(0)1594 564038 (Out of hours support) Back to top Jeremy Collins Guest Posted: Fri Jan 16, 2004 12:02 pm    Post subject: Re: Only One Instance. Ian Robinson wrote: Quote: I use this... hSem := CreateSemaphore (nil, 0, 1, PChar ('Nainosnibor')); Any particular design reasons for creating a semaphore, rather than a mutex? Just curious; most people go for the simpler call to CreateMutex. -- jc Remove the -not from email Back to top Display posts from previous: All Posts1 Day7 Days2 Weeks1 Month3 Months6 Months1 Year Oldest FirstNewest First         BorlandTalk.com Forum Index -> comp.lang.pascal.delphi.misc All times are GMT Goto page 1, 2  Next Page 1 of 2   Jump to: Select a forum C++ Builder Newsgroups----------------C++ BuilderC++ Builder (ActiveX)C++ Builder (Announcements)C++ Builder (Command Line Tools)C++ Builder DatabasesC++ Builder Databases (ADO)C++ Builder Databases (Desktop)C++ Builder Databases (InterBase Express)C++ Builder Databases (Multi-Tier)C++ Builder Databases (SQL Servers)C++ Builder (Graphics)C++ Builder (IDE)C++ Builder (Internet)C++ Builder (Internet Socket)C++ Builder (Internet Web)C++ Builder (Jobs)C++ Builder (Language)C++ Builder (Language C++)C++ Builder (Compatibility with MFC)C++ Builder (Native API)C++ Builder (Non-Technical)C++ Builder (Students)C++ Builder (Third Party Tools)C++ Builder (Upgrade)C++ Builder (VCL)C++ Builder (VCL Components Usage)C++ Builder (VCL Components Development)C++ Builder (VCL Usage)C++ Builder (WinAPI)C++ Builder Installation Delphi Newsgroups----------------Delphi (General)Delphi ActiveX Controls UsageDelphi ActiveX Controls DevelopmentDelphi As400Delphi DatabasesDelphi Databases (ADO)Delphi Databases (dbExpress)Delphi Databases (Desktop)Delphi Databases (InterBase Express)Delphi Databases (Multi-Tier)Delphi Databases (SQL Servers)Delphi DeploymentDelphi GraphicsDelphi IDEDelphi InternationalizationDelphi InternetDelphi Internet Isapi-WebBrokerDelphi Internet WebSnapDelphi Internet WinsockDelphi JobsDelphi Language BASMDelphi Language ObjectPascalDelphi Model Driven Architecture (General)Delphi Model Driven Architecture (Third Party)Delphi MultimediaDelphi Native APIDelphi Non-TechnicalDelphi ObjectPascalDelphi OLE AutomationDelphi OO designDelphi OpenToolsAPIDelphi Reporting-ChartingDelphi RTLDelphi StudentsDelphi TeamSourceDelphi Thirdparty ToolsDelphi Thirdparty Tools (General)Delphi Thirdparty Tools (IntraWeb)Delphi Thirdparty Tools (RaveReports)Delphi UpgradeDelphi VCLDelphi VCL ComponentsDelphi VCL Components UsingDelphi VCL Components WritingDelphi WebServices SOAPDelphi WinAPIDelphi XMLDelphi Installationcomp.lang.pascal.delphi.components.misccomp.lang.pascal.delphi.components.usagecomp.lang.pascal.delphi.components.writingcomp.lang.pascal.delphi.databasescomp.lang.pascal.delphi.misccomp.sources.delphi JBuilder Newsgroups----------------JBuilderJBuilder AnnouncementsJBuilder Applet IssuesJBuilder As400JBuilder CompilerJBuilder CORBA/RMIJBuilder DatabasesJBuilder DB SwingJBuilder DebuggerJBuilder DeploymentJBuilder DocumentationJBuilder EnterpriseJBuilder HandheldJBuilder IDEJBuilder JavaJBuilder JavaAPIJBuilder Java LanguageJBuilder Java SwingJBuilder Java BeansJBuilder Java Beans UsageJBuilder Java Beans DevelopmentJBuilder JBCLJBuilder JDataStoreJBuilder JobsJBuilder LinuxJBuilder MacintoshJBuilder & MobileSetJBuilder MultiLingual AppsJBuilder Non-TechnicalJBuilder OpenToolsJBuilder Servlets (JSP)JBuilder StudentsJBuilder Team DevelopmentJBuilder Thirdparty ToolsJBuilder UpgradeJBuilder Installation InterBase Newsgroups----------------InterBaseInterBase Bug DiscussionInterBase GeneralInterBase IBConsoleInterBase OpenSourceInterBase ReplicationInterBase SQLInterBase ThirdpartyInterBase Installation Miscellaneous Borland Newsgroups----------------AppCenterAppServerEnteraVisiBroker  You cannot post new topics in this forum You cannot reply to topics in this forum You cannot edit your posts in this forum You cannot delete your posts in this forum You cannot vote in polls in this forum Powered by phpBB © 2001, 2006 phpBB Group SEO toolkit © 2004-2006 webmedic.