Replace the >! operator with the >| operator that is more compliant with the POSIX standard

[liby]

Although the >! operator makes the code work, this implementation does not conform to the POSIX standard.

The POSIX compliant way to overwrite files without prompting is to use >| or >>| and this will work in any shell.

For information see here.

[tamcore]

If you have a look at #3 and #4, I'd argue that we can leave it as it is, as compatibility with any other shell besides zsh isn't really required here.