On Mon, 11 Apr 2011 19:45:10 +0200 José Mejuto <joshy...@gmail.com> wrote:
> Hello FPC-Pascal, > > Monday, April 11, 2011, 6:32:20 PM, you wrote: > > JL> Need to read the last 4 lines (txt) of a very large log file 100M bytes, > JL> 100k lines or more lots of times - of course I can read through the file > in > JL> the normal way but this is rather slow. Is there a way to 'read lines from > JL> the end'? I note that unix tail or its port to windows does this very fast > JL> so guess there must be a fast way to do it in pascal too? > > The idea is easy, instead reading forward, you read backwards in > blocks of, say, 64 Kb and count lines back. If not enougth lines you > insert another 64 Kb before and so on. Average line is usually less > than 100 bytes, so each 64 Kb are usually more than 600 lines. Read of > 64 Kb usually takes the same time as read any lower amount when the > block is 4096 bytes aligned. You can not really read backwards. You can use something like TFileStream.Seek(-4096,soEnd). Mattias _______________________________________________ fpc-pascal maillist - fpc-pascal@lists.freepascal.org http://lists.freepascal.org/mailman/listinfo/fpc-pascal
