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Math Forum » Discussions » Software » comp.soft-sys.matlab

Topic: Number of line in a text file
Replies: 12   Last Post: Jan 23, 2013 1:51 PM

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JWagberg

Posts: 138
Registered: 1/30/06
Re: Number of line in a text file
Posted: Nov 10, 2006 5:37 AM
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Benoît Valley wrote:
> Ok. I have now a very efficient way to know the number of line in my
> text file. Is it now possible to read very quickly just the last line
> of the file ?
> ...

If you know the maximum length, MAXLEN, of a line it's rather
straightforward:

open the file
use fseek to reposition the file position indicator MAXLEN+1 chars from
the end
read to end of file in one chunk
find the chars between the penultimate and last newline

If you don't know MAXLEN, you have to choose some appropriate MAXLEN,
read a chunk and, if there is no newline in the chunk, reposition with
fseek and read in the previous chunk.

In this case you also have to deal with the fact that the line you are
looking for can span more than one chunk.

jewa & wagberg , net

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