Shell Programming and Scripting

     echo [-neE] [arg ...]
          Output the args, separated by  spaces,  followed  by  a
          newline.   The  return  status  is  always 0.  If -n is
          specified, the trailing newline is suppressed.  If  the
          -e  option  is  given,  interpretation of the following
          backslash-escaped characters is enabled.  The -E option
          disables the interpretation of these escape characters,
          even on systems where they are interpreted by  default.
          echo  does not interpret -- to mean the end of options.
          echo interprets the following escape sequences:
          \a   alert (bell)
          \b   backspace
          \c   suppress trailing newline
          \e   an escape character
          \f   form feed
          \n   new line
          \r   carriage return
          \t   horizontal tab
          \v   vertical tab
          \\   backslash
          \nnn the character whose ASCII code is the octal  value
               nnn (one to three digits)
          \xnnn
               the character whose ASCII code is the  hexadecimal
               value nnn (one to three digits)

 $ { AAA="a\nb\nc"; echo -e $AAA; }

a
b
c

 $ { AAA="a\nb\nc"; echo $AAA; }

a\nb\nc