This entire reply is anti-helpful, serving only to distract from the simple, one-line solution to the OP's problem: the "N" format to pack is 32-bit, so it won't work with offsets larger than 2^32. The "Q" format is 64-bit, so it will.

In reply to Re^2: index for large text file by educated_foo
in thread index for large text file by cafeblue

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