I have looked at the example in http://docs.openhab.org/addons/bindings/exec/readme.html#full-example
Thing exec:command:myscript [command=“php ./configurations/scripts/script.php %2$s”, transform=“REGEX((.*?))”]
I have in my default.things
Thing exec:command:elkedel_voltage [command="/usr/local/bin/tplink-smartplug.py -t 192.168.1.20 -j '{\"emeter\":{\"get_realtime\":{}}}'", interval=15,timeout=4,transform="REGEX(\"voltage\":(\\d*?))"]
Thing exec:command:elkedel_power [command="/usr/local/bin/tplink-smartplug.py -t 192.168.1.20 -j '{\"emeter\":{\"get_realtime\":{}}}'", interval=15,timeout=4,transform="REGEX(\"power\":(\\d*?))"]
Thing exec:command:elkedel_command [command="/usr/local/bin/tplink-smartplug.py -t 192.168.1.20 -c %2$s", interval=15,timeout=4"]
But I get the error in the log:
2017-03-16 00:06:16.083 [ERROR] [hab.binding.exec.handler.ExecHandler] - An exception occurred while formatting the command line with the current time and input values : 'Format specifier '%2$s''
If I change the format to \%2$S it works.