First, put the CSV files or other files in a Folder
Use an editor for create the script Header_add_to_CSV_files.sh
Paste the content this Header_add_to_CSV_files.sh and save.
Make this executable : chmod a+x Header_add_to_CSV_files.sh Execute : ./Header_CSV_add_true_09.sh /Path/To/Files/
This script adds the headers to files.