On 2007-10-16 16:46, sylvaticus wrote:
> Hello,
> is it possible to append some data on a text output file appending
> the data to each row, and without use too much computational I/O ??
>
> Instead of the classical way:
>
> VARX VARY VARZ...
> year1 x1 y1 z1
> year2 x2 y2 z2
>
> .. I would like to use the much more redeable:
>
> year1 year2 ..
> VARX x1 x2 ...
> VARY y1 y2 ...
> VARZ z1 z2 ...
> ...
>
> where the 1,2 series are wrote at different times.. a sort of a
> appendByRow() function.. and I would avoid of loading the whole file
> in memory and then printing it line-by-line, as I have to do it on
> approx 40,000 (few KB) files.. and I am worry that the second approach
> would take years :-)))

Files of that size is really nothing much for a modern computer, not
even if there are 40,000 of them. In fact, you could probably load them
all into memory without much trouble (though I think that it would be
faster to just open them one by one).

> is it possible to do it in a efficient way (e.g. seeking to the right
> place, delete the newline and appending there) ??

While such an approach would be possible it would require reading the
whole file into a buffer large enough to hold the final result, and
would involve a lot of copying making it very slow. By operating on one
line at at time you get much better memory usage and a much better design.

--
Erik Wikström