The >> operator redirects output to a file and the output will be appended at the end of the file.
You can use the echo command to append the text to the end of the file as shown.
# echo "/mnt/pg_master/wal_archives 10.20.20.5(rw,sync,no_root_squash)" >> /etc/exports
Alternatively, you can use the printf command (do not forget to use \n character to add the next line).
# printf "/mnt/pg_master/wal_archives 10.20.20.5(rw,sync,no_root_squash)\n" >> /etc/exports
The tee command copies text from standard input and pastes/writes it to standard output and files. You can use its -a flag to append text to the end of a file as shown.
# echo "/mnt/pg_master/wal_archives 10.20.20.5(rw,sync,no_root_squash)" | tee -a /etc/exports
OR
# cat shares.txt | tee -a /etc/exports
