[fpc-pascal] read lines at end of file

José Mejuto joshyfun at gmail.com
Mon Apr 11 19:45:10 CEST 2011

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.

Best regards,

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