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    copied!<p>After searching online for a while, I didn't find any good examples.</p> <p>Here are two calls to CreateFile with the intent of locking the file for the life of a process... I use this along side the <a href="http://support.microsoft.com/kb/243953" rel="nofollow">CLimitSingleInstance</a> that uses CreateMutex for a global named mutex.</p> <p>The first call to CreateFile attempts to open it, the second one creates it if necessary. I have a little bit more thorough implementation. I implemented it in Qt, hence the qCritical() instead of std::cout and the QDir::tempPath() instead of getting that some other way.</p> <pre><code>class SingleInstance { protected: DWORD m_dwLastError; HANDLE m_hFile; public: SingleInstance(const char *strMutexName) { } bool attemptToLockTempFile() { QString lockFile = QDir::tempPath() + "/My.exe.lock"; m_hFile = CreateFileA(lockFile.toLocal8Bit().data(), GENERIC_READ, 0, NULL, OPEN_EXISTING, 0, NULL); DWORD dwLastError = GetLastError(); if(m_hFile != NULL &amp;&amp; m_hFile != INVALID_HANDLE_VALUE) { return true; } else { if(dwLastError == ERROR_FILE_NOT_FOUND ) { m_hFile = CreateFileA(lockFile.toLocal8Bit().data(), GENERIC_READ, 0, NULL, CREATE_NEW, 0, NULL); dwLastError = GetLastError(); if(m_hFile != NULL &amp;&amp; m_hFile != INVALID_HANDLE_VALUE) { return true; } else if(dwLastError == ERROR_SHARING_VIOLATION) { qCritical() &lt;&lt; "Sharing Violation on My.exe.lock"; } else { qCritical() &lt;&lt; "Error reading" &lt;&lt; "My.exe.lock" &lt;&lt; "-" &lt;&lt; dwLastError; } } else if(dwLastError == ERROR_SHARING_VIOLATION) { qCritical() &lt;&lt; "Sharing Violation on My.exe.lock"; } else { qCritical() &lt;&lt; "Unable to obtain file lock -" &lt;&lt; dwLastError; } return false; } } ~SingleInstance() { if ( m_hFile != NULL &amp;&amp; m_hFile != INVALID_HANDLE_VALUE) { ::CloseHandle(m_hFile); //Do as late as possible. m_hFile = NULL; } } } </code></pre> <p>Here is what you would have at the top of your main function:</p> <pre><code>SingleInstance g_SingleInstanceObj(globalId_QA); // Makes sure that the program doesn't run if there is another // instance already running if (g_SingleInstanceObj.IsAnotherInstanceRunning()) { return 0; } </code></pre>
 

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