[jmcnulty]

It's the read/readarray builtin that's creating the tmpfiles and that's not great, but the string substitution doesn't. My point was there's no need to call out to another program to do something that bash is capable of doing itself.

[chubot]

No, it's the here doc, including here strings. See the blog post, which doesn't use read or readarray.

[jmcnulty]

Understand. Did some quick tests myself and see what you mean.

Here's a version that doesn't use "here string" and so doesn't create temporary files.

  #!/bin/bash

  shopt -s lastpipe

  string="Los Angeles, London, Belfast, New York"
  echo "${string/, /,}" | readarray -d, -t arrayA
  echo ${arrayA[0]}
  echo ${arrayA[1]}

Also, the lastpipe option runs the readarray in the context of the current process.