unix sort on multiple columns

For the nth time today, i had to think how to do unix sort on multiple columns either based on numbers or alphabets. Fortunately, i had a coffee before, so i figured out that for sorting a file that looks like this:


chr01 1
chr01 10
chr01 2
chr01 5
chr01 8
chr02 9
chr02 9
chr02 19
chr02 98
chr02 92

you can run the command "sort -k1,1 -k2n,2 sorttest" from GNU coreutilities to get something that looks like this:


chr01 1
chr01 2
chr01 5
chr01 8
chr01 10
chr02 9
chr02 9
chr02 19
chr02 92
chr02 98

and run the command "sort -k1,1 -k2,2 sorttest" to get something that looks like this:

chr01 1

chr01 10

chr01 2

chr01 5

chr01 8

chr02 19

chr02 9

chr02 9

chr02 92

chr02 98

All commands were run using "GNU coreutils 8.12.197-032bb" compiled on September 2011 as part of the Ubuntu OS.