Append text following each line matched by address. If text goes over more than one line, newlines must be “escaped” by preceding them with a backslash. The text will be terminated by the first newline that is not escaped in this way. The text is not available in the pattern space, and subsequent commands cannot be applied to it. The results of this command are sent to standard output when the list of editing commands is finished, regardless of what happens to the current line in the pattern space.
$a\ This goes after the last line in the file\ (marked by $). This text is escaped at the\ end of each line, except for the last one.