| Manipulate Columns in Text Files |
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| Saturday, 09 February 2008 | |
 Suppose we have a file, called equipment.lst, with data organized in several columns. Each column is separated by a space. Assume also that the cardinality of the file is big. 1. Mouse 102 -29 45 -1 2. Harddisk 23 -34 21 0 3. LCD+Monitor 1234 -2 1 22 2 4. Laser+Printer 2222 -3 23 90 -2 5. Memori 23 -4 56 7 6. LCD+Projector 342 5 43 -1 : : 900000. IBM+Thinkpad+Laptop 342 33 22 11 A quick and easy way to only take the name of the equipments, i.e. the second column, is to use cut command: cut equipment.lst -f2 > equipment_name.lst Another way is to use awk command: cat equipment.lst | awk -F ' ' '{print $2}' > equipment_name.lst Or, if we want to store only the unique name of the equipments, we can add sort command with pipelining: cut equipment.lst -f2 | sort -u > equipment_unique_name.lst But, how about if we want to store only the first 10000 or the last 5000 rows? Just use head or tail command: head -10000 equipment.lst | awk -F ' ' '{print $2}' > equipment_name.lst Or, cut equipment.lst -f2 | head -10000 > equipment_unique_name.lst Using tail command: tail -5000 equipment.lst | awk -F ' ' '{print $1}' > equipment_name.lst Or, cut equipment.lst -f2 | tail -5000 > equipment_name.lst |
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