sed edit file in place

Question

I am trying to find out if it is possible to edit a file in a single sed command without manually streaming the edited content into a new file and

Answer 1

mv file.txt file.tmp && sed 's/foo/bar/g' < file.tmp > file.txt

Should preserve all hardlinks, since output is directed back to overwrite the contents of the original file, and avoids any need for a special version of sed.