How to check if a process is running using Delphi?

Question

Similar to this question, but in Delphi:

How do I find out if a process is already running using c#?

I have an updater program, I want it to check the progra

Answer 1

If you have control over the application (as is implied from your question), a nice way to do this is to create a named file mapping object early in the process starts. This is similar to the suggestion of creating a mutex from RedLEON.

// Add this into the application you wish to update
CreateFileMapping(HWND($FFFFFFFF), nil, PAGE_READONLY, 0, 32, 'MAIN-PROGRAM');
// Note: Mapping object is destroyed when your application exits

// Add this into your updater application       
var
    hMapping: HWND;
begin
    hMapping := CreateFileMapping(HWND($FFFFFFFF), nil, PAGE_READONLY, 0, 32, 'MAIN-PROGRAM');
    if (hMapping <> 0) then
        begin
        if (GetLastError() = ERROR_ALREADY_EXISTS) then
            ShowMessage('Application to update is already running!');
        end;

Check out the MSDN documentation on CreateFileMapping for further details.

See also the accepted answer to this question which covers Luke's answer and provides additional solutions.