How do I pass a stored value as the column number parameter to edit in awk?

I have a .dat file with | separator and I want to change the value of the column which is defined by a number passed as argument and stored in a var. My code is

awk -v var="$value" -F'|' '{ FS = OFS = "|" } $1=="$id" {$"\{$var}"=8}1'   
myfile.dat > tmp && mv tmp myfiletemp.dat

This changes the whole line to 8, obviously doesn't work. I was wondering what is the right way to write this part

{$"\{$var}"=8}1

For example, if I want to change the fourth column to 8 and I have value=4, how do I get {$4=8}?

• Referring to a variable with a $ in front of it turns it in to a reference to the column. So i=3; print $i; print i will print the third column and then the number 3.
• Passing all your variables as options will avoid any problems with trying to interpolate bash variables inside your awk code, which either won't work (with single-quoted code) or be very messy.
• The -F option specifies FS for you, so using that and setting it in your code is redundant.

Here's how I would do this:

#!/bin/bash
column=4
value=8
id=1
awk -v col="$column" -v val="$value" -v id="$id" '
    BEGIN {FS=OFS="|"}
    $1==id {$col=val}
    print
' myfile.dat > myfiletemp.dat

Given this input:

1|34|test|should be 8|8583|foo
2|68|test|should be left alone|5828|bar
3|61|test|should be left alone|6682|baz

This is the output:

1|34|test|8|8583|foo
2|68|test|should be left alone|5828|bar
3|61|test|should be left alone|6682|baz