Do not recommend sleeping when using vipw(8) non-interactively Before r231383, pw_edit(3) was unable to detect file changes with happening within the same second. Since that revision, however, pw_edit(3) has a nanosecond precision of detecting file modifications, so calling "sleep 1" when using a non-interactive editor with vipw(8) is no longer necessary.
I am not exactly sure if this change is correct, I don't know if a nanosecond is precision can be considered "atomic" on FreeBSD.