Running Gretl 1.8.3 on Mac OS X 10.5.8
Running in a script the command
open test1.ods --sheet=2
gives an error message: Error executing script: halting
Doing this without the --sheet option works with no errors.
Also doing this with an .xls also works.
Also: the append command does not accept --sheet, --rowoffset etc. I have not tested --rowoffset etc on the open command.