title: Is that possible to mmap a very big file and using qsort?
body: <p>I have to sort a large amount of data that can not fit in memory, and one thing could do this I know is "external sort". But I am wondering is that possible to mmap this large data file, and use 'qsort' as it is a 'normal data array'? If that's feasible, what's the differences with 'external sort'?</p>