Thanks for the tip. I should have also mentioned in my post that the input file is huge (of the order of 10GBs or so) and the indices i,j which I am be looking for are usually a million apart.

So I can preprocess the fileand concatenate the strings etc. - but I was hoping that I could just include a "\n" into my expression and it will take care of the matching - even on my original input file. That would be much easier.

ddrudik - Thanks for your kind help anyway.