Yes. And it requires 4 passes of the dataset, including two full sorts.
The number of passes isn't really relevant - the sorts maybe. But the main reason I posted the one-liner was that you appear to suggest that the sort solution wouldn't work if you wanted to keep order.
I use 5 passes ('a-e','f-j', 'k-o', 'p-t', 'u-z') on the same dataset.
And that shows the weakness of your approach. It requires a priory knowledge about the keys. A bad pick of dividing the keys may lead to almost all the keys being handled in the same pass. You'd need to tune your program for different datasets.

In reply to Re^4: Huge files manipulation by JavaFan
in thread Huge files manipulation by klashxx

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