Question

Given a list like:

Dog bone
Cat catnip
Human ipad
Dog collar
Dog collar
Cat collar
Human car
Human laptop
Cat catnip
Human ipad

How can I get results like this, using awk:

Dog bone 1
Dog collar 2
Cat catnip 2
Cat collar 1
Human car 1
Human laptop 1
Human ipad 2

Do I need a sub array? It seems to me like a need an array of “owners” which is populated by arrays of “things.”

I’d like to use awk to do this, as this is a subscript of another program in awk, and for now, I’d rather not create a separate program.

By the way, I can already do it using sort and grep -c, and a few other pipes, but I really won’t be able to do that on gigantic data files, as it would be too slow. Awk is generally much faster for this kind of thing, I’m told.

 Thanks, 
 Kevin

EDIT: Be aware, that the columns are actually not next to eachother like this, in the real file, they are more like column $8 and $11. I say this because I suppose if they were next to eachother I could incorporate an awk regex ~/Dog\ Collar/ or something. But I won’t have that option. -thanks!

Answer 1

awk does not have multi-dimensional arrays, but you can manage by constructing 2D-ish array keys:

awk '{count[$1 " " $2]++} END {for (key in count) print key, count[key]}' | sort

which, from your input, outputs

Cat catnip 2
Cat collar 1
Dog bone 1
Dog collar 2
Human car 1
Human ipad 2
Human laptop 1

Here, I use a space to separate the key values. If your data contains spaces, you can use some other character that does not appear in your input. I typically use array[$a FS $b] when I have a specific field separator, since that’s guaranteed not to appear in the field values.