Instead of inheriting the permissions from the tmp directory, new files should
have permissions that reflect the defaults on the system taking umask into
account.
It seems that (unix) permissions of 666 - umask are as close to a standard as
anything [1] and that 'touch' uses this. On Windows it seems sensible to just
use 644 directly [2].
[1] http://unix.stackexchange.com/a/102080
[2] http://ruby-doc.org/core-1.9.3/File.html
Robert Haines