Thanks for the interesting example... I had to try it as the times you quoted seemed very fast. But on my P4 with 512Mb RAM, and <who knows?> disc speed your program creates the file in around 3.5 secs!

However the "converted file" only contained "\n"s.

I'm no guru, but I worked out that (I think) you need a split before the join, or you won't have a list that join requires.

print OUTFILE join (",",  (split /(XXXXXXXXXX)/)), "\n";

worked, sort of, for me - I couldn't get your /(.{,10})/ pattern to work, although I think I understand what it's trying to match - any 10 chars exactly and reflect those in the stream as well as the other characters - which in this case aren't any. The resulting file simply had "\n"s as the split didn't seem to find a match.

This then took around 20 seconds...

$ perl file.pl
Creating file took 3.40489602088928 seconds
Splitting file using regexp took 19.5581229925156 seconds

[download]

This results in lines containing collections of 10 sets of the following ",XXXXXXXXXX," so that 2 commas appear between adjacent groups of X's and at the beginning and end of each line.

In reply to Re: Re: What's the most efficient way to write out many lines of data? by hagen
in thread What's the most efficient way to write out many lines of data? by Anonymous Monk

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