I am trying to use `awk` to print variables from various columns in a line delimited by `,` .The columns and pattern which I want to print is stored in another variable `b`.
The pattern `a` and print patter `b` are given below:

```
a='15986327,415532694,850257614,875121642,20140819'
b='$1","$2","$4'

```

I am trying to get the output as below.

```
15986327,415532694,875121642

```

I am trying to pass the pattern `b` to awk using `-v` switch but not sure how to use that with `print` inside `awk`. Tried below commands but this is not the output I was trying to get to.

```
echo $a |awk -v ba="${b}" -F"," '{print ba}'
$1","$2","$4

echo $a |awk -v ba="${b}" -F"," '{print $ba}'
15986327,415532694,850257614,875121642,20140819

```