Print a column with awk inside a for loop

Question

I want to print $2 however inside a for loop. I tried with the following

for i in {2,3,4,5,6,7,8,9,10,11,12,13,14,15,16,17,18,19,21}; do
awk '{ print $${i} }' COLVAR >tmp_${i}
done

It gives syntax error. I tried also with ${${i}} but still the syntax error. I am not sure what is wrong.

This is really bad design to have a loop in the shell to print columns in `awk` when you can do with `awk` itself — Inian, Apr 27 '18 at 19:39
Sorry I am a newbie and trying to learn. Please bear with me — Soumendranath Bhakat, Apr 27 '18 at 19:45

score 0 · Answer 1 · answered Apr 27 '18 at 19:45

$ cat file
a b c d e

To use shell variables in awk, use -v:

$ for i in 2 3 4; do awk -v i=$i '{ print $i }' file; done
b
c
d

Usually the best is to do something like this entirely in awk:

$ awk 'BEGIN { split("2 3 4", a) } { for (i in a) print $i }' file
a
b
c

1 Answers1