It looks like Scrutinzer's suggestion should work just fine as long as:So:I would do it slightly differently (to quit after the desired transaction is found):

Code:

awk '{p=p $0 RS} /EOT/{if(p~s){printf "%s",p;exit}else p=x}' s="~$trannum~" file

which should cut the time awk spends reading your large file about in half, on average.

But, the way to make big gains here would be to search for and extract multiple transactions in a single pass through your large file. If you could, for example, extract 10 transactions at a time, you would only have to read the large file once instead of 10 times and you would only have to invoke awk once instead of 10 times; both of which would be big wins for performance.

Note that extracting 10 transactions at a time does not mean that the extracted transactions would all be saved in a single file; each transaction could easily be extracted into a separate file. And, 10 is just an example; an awk script could easily extract thousands of transactions into separate files in a single pass through your large transaction file increasing your script's processing speed immensely if your script is being used to process thousands of transactions. Note also that this is why we want details about what you are doing instead of vague statements about a tiny piece of the script you are writing. The more we know, the better chance we have of making a suggestion that will significantly improve your script.