Using variables in printf format

Question

Suppose I have a file like this:

$ cat a
hello this is a sentence
and this is another one

And I want to print the first two columns with so

Answer 1

you can use eval (maybe not the most beautiful with all the escape characters, but it works)

i=15
eval "awk '{printf \"%$i-s%s\\n\", \$1, \$2}' a"

output:

hello          this
and            this