These interpolated strings can be safely entered into preferences dialog text areas or entered into the config file with a text editor. It is not safe to use interpolated strings in the profile sections.
It is possible to use configuration file options in the value of other options. An example:
[DEFAULT]
interface = wlan1
[DHCP]
pidfile = /etc/dhcpc/dhcpcd-%(interface)s.pid
means that WiFi Radar will use the file /etc/dhcpc/dhcpcd-wlan1.pid for the DHCP PID file.
This is used most heavily in the DHCP and WPA sections of the config file. In fact, the default values for those sections are:
[DHCP]
args = -D -o -i dhcp_client -t %(timeout)s
command = dhcpcd
kill_args = -k
pidfile = /etc/dhcpc/dhcpcd-%(interface)s.pid
timeout = 20
[WPA]
args = -B -i %(interface)s -c %(configuration)s -D %(driver)s -P %(pidfile)s
command = /usr/sbin/wpa_supplicant
configuration = /etc/wpa_supplicant.conf
driver = wext
kill_command =
pidfile = /var/run/wpa_supplicant.pid
To use interpolated strings, surround any option from the config file with %( and )s. So, to use the interface option from the DEFAULT section in the value of any other option, use %(interface)s in the options value.