in reply to fast lookups in files

If key and have fixed length (for example both 32 bit integers), you could write it into a binary and do a binary search.

I think there is also a small unix tool that does line based binary search in files, but I can't remember the name. Update: It seems look (1) (in Debian shipped with in the bsdmainutils package) does the trick, but I'm not sure if it works with numerically sorted lines.

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Re^2: fast lookups in files
by bart (Canon) on Feb 05, 2008 at 13:01 UTC
    ...but I'm not sure if it works with numerically sorted lines.
    Then make a processed copy of the file, where you pad the numbers to the right to a fixed length, with sprintf, so they sort the same numerically and asciibetically.
[reply]
      Right, but again it requires the size of the index to be known in advance - in which case you can use the binary data much more efficient.
[reply]
        If you plan to store the numbers as binary data in the file: note that positive big endian integers also sort properly asciibetically. Use the "N" template for pack.
[reply]

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