in linux

Write a unix command that reads the datastream onstandard input and writes it all to standard output, changing every'a' to a ' z ' and every ' b ' to an 'a' and every ' c ' to a ' b ' and every'd' to a ' c ' and so on. In other words, every letter is replaced bythe preceding letter, except for ' a ' which is replaced by ' z '.(Write your arguments in the most natural way possible.)