http://www.unix.com – Hello, I have 2 files. One has a list of serial numbers: Code: 12345_7 2345_9 35454 4759:1 PEP8794 The other is an excel file, with multiple columns, separated by tab: Code: 12345_7 ... ... .. .. .. .. .. 2345_9 ... ... .. .. .. .. .. 35454 ... ... .. .. .. .. .. 4759:1 ... ... .. .. .. .. .. YEP0994 ... ... .. .. .. .. .. TAHT7878 ... ... .. .. .. .. .. AGCRT99 ... ... .. .. .. .. .. I want the following output, with an extra column added to the excel file, if the serial number is found in file 1, and leave the column "blank" if not foun (HowTos)