Feature Request: -Backup

[NickCraver]

Can we add a -Backup flag (or maybe it takes a path)? e.g. hosts.bak is created before write operations? This would act as a nice failsafe when anything goes wrong.

[richardszalay]

As an alternative, what if write fails were caught and the contents were instead saved to a temp file (the location of which was included in the error message)?