Enable duplex printing on macOS (without admin rights)

Our student users don’t have admin rights, so the printer’s PPD file had to be adapted: DefaultAPOptionalDuplexer from False to True.

The trick is an in-place sed:

sed -i '' 's/*search_string/*replace_string/g' /path/to/file.extension

-i '' writes the change back into the same file (on macOS there is a space between -i and the empty quotes).

# change duplex
Printer_X=$(grep "*DefaultAPOptionalDuplexer: False" /private/etc/cups/ppd/Printer_X.ppd)

if [ "$Printer_X" == "*DefaultAPOptionalDuplexer: False" ]; then
    echo "change Printer_X to duplex"
    sed -i '' 's/*DefaultAPOptionalDuplexer: False/*DefaultAPOptionalDuplexer: True/g' /private/etc/cups/ppd/Printer_X.ppd
else
    echo "not needed"
fi