How to Replace a line in the same file by SED in Unix Shell scripting?

Question

In Reference to this question After getting the line identifier matching in first and second file I need to replace the line in first file with the line of second file.For that

Answer 1

Have a look at sponge which is part of moreutils.

e.g.

% sed "s/root/toor/" /etc/passwd | grep -v joey | sponge /etc/passwd