asked on

Check that a specific executable runs in Windows

I wrote a Delphi application, says myapp.exe that should preferrably test when starting that there is no other instance running and, if so, halt. In a first stage, I used a counter in the registry that I put on 1 when starting and 0 when terminating and I tested it at startup. But if for some reason the program aborts, it can't be started because the flag is on 1 and I do not want to ask the user something like 'it looks like this is already running, do you want to continue ?'. I prefer to detect the other really running. Is there some API do check this ?

Motaz

you can use FindWindow API by one of two methods:

1. You didn't know main application form class name such as TfmMain, and you are sure of the main application
caption such as (My Application Caption)

if FindWindow(nil, 'My Application Caption') > 0 then
ShowMessage('Application is running')
else
ShowMessage('Application is not running');

2. You know main form's class name:

if FindWindow('TfmMainApp', nil) > 0
ShowMessage('Application is running')
else
ShowMessage('Application is not running');

You should do that in an external application, for example a gaurd for your main application
Motaz

-Yoshi-

Since you could relay on that windows locks the executable for writing as soon as you start it the first time you could simply test that.. I'm not about the best way to do this but this is one way..

function IsOpen(AAppName: String): Boolean;
var
FApp: TFileStream;
begin
try
FApp:= TFileStream.Create(AAppName, fmOpenWrite);
Result:= False;
FApp.Free;
except
Result:= True;
end;
end;

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-Yoshi-

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-Yoshi-

This should work though....

function TForm1.AlreadyOpen: Boolean;
var
FTmpHandle: HWND;
FTitle: String;
begin
// Searching all next windows
FTmpHandle:= GetNextWindow(Handle, GW_HWNDNEXT);
while (GetNextWindow(FTmpHandle, GW_HWNDNEXT) <> 0) do
begin
FTmpHandle:= GetNextWindow(FTmpHandle, GW_HWNDNEXT);
SetString(FTitle, PChar(nil), GetWindowTextLength(FTmpHandle));
GetWindowText(FTmpHandle, PChar(FTitle), MaxInt);
if (FTitle=Application.Title) then
begin
Result:= True;
Exit;
end;
end;

// Searching all previous windows
FTmpHandle:= GetNextWindow(Handle, GW_HWNDPREV);
while (GetNextWindow(FTmpHandle, GW_HWNDPREV) <> 0) do
begin
FTmpHandle:= GetNextWindow(FTmpHandle, GW_HWNDPREV);
SetString(FTitle, PChar(nil), GetWindowTextLength(FTmpHandle));
GetWindowText(FTmpHandle, PChar(FTitle), MaxInt);
if (FTitle=Application.Title) then
begin
Result:= True;
Exit;
end;
end;

Result:= False;
end;

-Yoshi-

Had some fun rewriting the function... Enjoy!

function TForm1.AlreadyOpen: Boolean;
function GetTitle(AHandle: HWND): String;
begin
SetString(Result, PChar(nil), GetWindowTextLength(AHandle));
GetWindowText(AHandle, PChar(Result), MaxInt);
end;

function Search(AHandle: HWND; AFlag: Cardinal): Boolean;
begin
AHandle:= GetNextWindow(AHandle, AFlag);
if (AHandle <> 0) then
if (GetTitle(AHandle)=Application.Title) then
Result:= True
else
Result:= Search(AHandle, AFlag) { Recursive call }
else
Result:= False;
end;
begin
Result:= Search(GetNextWindow(Handle, GW_HWNDNEXT), GW_HWNDNEXT) or
Search(GetNextWindow(Handle, GW_HWNDPREV), GW_HWNDPREV)
end;

Member_2_248744

hello Flupmans , you might look at

https://www.experts-exchange.com/questions/10323536/Preventing-another-instance-in-systray.html?query=CreateMutex&searchType=topic

Flupmans

ASKER

For me indeed, checking that myapp.exe is locked is enough as I start it from another .exe