Hi,
++andreas1234567, yes, that will work, but you will always fill your memory with a lot of unnecessary data before you actually output any data.
Without saying too much (to not make the OP's homework too easy ;-)), I'd first find out which column is actually searched for, then go through the rest of the file line by line and print the only column that is requested.
No building up of a huge hash...
Regards,
svenXY