Assigning printf output to a variable in awk command

Question

I want to put leading 0 characters to some input, resulting in a fixed length (length given by a variable). The input can be a number or a string.
I want to catch the output in a variable.

I tried this:

awk '{j=$(printf "%04d\n"); echo $j}'  

but it is throwing this error:

awk: line 1: syntax error at or near printf

Answer 1

Use

 awk '{j=sprintf("%04d", NR); print j}' 

to put the record number in the variable j.