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copied!<blockquote> <p>"I would probably create a new file, seek in the old file, do a buffered read/write from old file to new file, rename the new file over the old one."</p> </blockquote> <p>I think you'd be better off simply:</p> <pre><code>#include <fstream> std::ifstream ifs("logfile"); //One call to start it all. . . ifs.seekg(-512000, std::ios_base::end); // One call to find it. . . char tmpBuffer[512000]; ifs.read(tmpBuffer, 512000); //One call to read it all. . . ifs.close(); std::ofstream ofs("logfile", ios::trunc); ofs.write(tmpBuffer, 512000); //And to the FS bind it. </code></pre> <p>This avoids the file rename stuff by simply copying the last 512K to a buffer, opening your logfile in truncate mode (clears the contents of the logfile), and spitting that same 512K back into the beginning of the file.</p> <p>Note that the above code hasn't been tested, but I think the idea should be sound.</p> <p>You could load the 512K into a buffer in memory, close the input stream, then open the output stream; in this way, you wouldn't need two files since you'd input, close, open, output the 512 bytes, then go. You avoid the rename / file relocation magic this way.</p> <p>If you don't have an aversion to mixing C with C++ to some extent, you could also perhaps:</p> <p>(Note: pseudocode; I don't remember the mmap call off the top of my head)</p> <pre><code>int myfd = open("mylog", O_RDONLY); // Grab a file descriptor (char *) myptr = mmap(mylog, myfd, filesize - 512000) // mmap the last 512K std::string mystr(myptr, 512000) // pull 512K from our mmap'd buffer and load it directly into the std::string munmap(mylog, 512000); //Unmap the file close(myfd); // Close the file descriptor </code></pre> <p>Depending on many things, mmap <em>could be</em> faster than seeking. Googling 'fseek vs mmap' yields some interesting reading about it, if you're curious.</p> <p>HTH</p>

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