Hi guys, I have a file with over 30 million lines (Txn IDs) over a period of 11 years. I want to delete from that file (it's a flat file, not a db table) lines that dont begin with certain characters. Or alternatively, create another file for lines that begin with certain characters. The format of the ID is DATE:<SOME.SEQ.NOs>(Of course, there are multiple txns per day) So for instance it will have 20080101XXXXXXXX - For transactions done on 1st Jan 2008, 20130613XXXXXX for today's txn, etc My requirement is to get a list of transactions done say from Jun 2010 to Jun 2011. Therefore, I should somehow either: a) Create a new file by piping output of grep ^2010 and grep ^2011 (Challenge is how to get only for 2010[06,07,08.09,10,11 and 12] and not entire 2010. Same for 2011) b) Delete the lines that dont match a) above. I dont want to go this route. Tools available: Ubuntu 12.04 HP-UX 11.31 PS: I don't know if the subject matches my requirement but ...