title: Iterating over two lists in parallel in /bin/sh
body: <p>I have two lists of equal length, with no spaces in the individual items:</p>
  
  <pre><code>list1="a b c"
  list2="1 2 3"
  </code></pre>
  
  <p>I want to iterate over these two lists in parallel, pairing a with 1, b with 2, etc.:</p>
  
  <pre><code>a 1
  b 2
  c 3
  </code></pre>
  
  <p>I'm attempting to support modern portable Bourne shell, so Bash/ksh arrays aren't available. Shelling out to awk would be acceptable in a pinch, but I'd rather keep this in pure sh if possible.</p>
  
  <p>Thank you for any pointers you can provide!</p>