Be aware that bash doesn't like being piped, and changes some of its behaviour. I work around that using expect:

- Here's the script itself https://github.com/Warbo/warbo-utilities/blob/master/raw/wra...

- Here's the accompanying expect file https://github.com/Warbo/warbo-utilities/blob/master/raw/wra...

- Here's my patched version of GNU fold, which removes some buffering https://github.com/Warbo/warbo-utilities/blob/master/raw/fol...

- Here's the resulting Nix package (along with some tests) https://github.com/Warbo/warbo-utilities/blob/master/scripts...