4.40. How do I read (insert/add) a file at the top of a textfile?

Normally, adding a "header" file to the top of a "body" file is done from the command prompt before passing the file on to sed. (MS-DOS below version 6.0 must use COPY and DEL instead of MOVE in the following example.)

       copy header.txt+body temp                  # MS-DOS command 1
       echo Y | move temp body                    # MS-DOS command 2
                                                    #
       cat header.txt body >temp; mv temp body    # Unix commands

However, if inserting the file must occur within sed, there is a way. The sed command "1 r header.txt" will not work; it will print line 1 and then insert "header.txt" between lines 1 and 2. The following script solves this problem; however, there must be at least 2 lines in the target file for the script to work properly.

     # sed script to insert "header.txt" above the first line
     1{h; r header.txt
       D; }
     2{x; G; }
     #---end of sed script---