Have you tried "grep" yet to see if the result returns in acceptable time?

Hi, I was playing around somemore with it, and found that the fastest search is perl's regex engine

   # slurp file into $buf
   if( $buf =~ /($searchnum)/ ){....}
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This was faster than running backticks with the c grep.

So I guess the trick is decide on how much memory you want to use at any one moment, read in overlapping segments of the file of that size, then regex it.