[SOLVED] How to implement awk using loop variables for the row?

How to implement awk using loop variables for the row?

I have a file with n rows and 4 columns, and I want to read the content of the 2nd and 3rd columns, row by row. I made this

awk 'NR == 2 {print $2" "$3}' coords.txt

which works for the second row, for example. However, I'd like to include that code inside a loop, so I can go row by row of coords.txt, instead of NR == 2 I'd like to use something like NR == i while going over different values of i.

I'll try to be clearer. I don't want to wxtract the 2nd and 3rd columns of coords.txt. I want to use every element idependently. For example, I'd like to be able to implement the following code

for (i=1; i<=20; i+=1)
        awk 'NR == i {print $2" "$3}' coords.txt > auxfile
        func(auxfile)
end

where func represents anything I want to do with the value of the 2nd and 3rd columns of each row.

I'm using SPP, which is a mix between FORTRAN and C.

How could I do this? Thank you

Solution

It is of course inefficient to invoke awk 20 times. You'd want to push the logic into awk so you only need to parse the file once.

However, one method to pass a shell variable to awk is with the -v option:

for ((i=1; i<20; i+=2))  # for example
do
    awk -v line="$i" 'NR == line {print $2, $3}' file
done

Here i is the shell variable, and line is the awk variable.