The function comedi_command() starts streaming input or output. The command structure pointed to by the parameter command specifies the acquisition. The command must be able to pass comedi_command_test() with a return value of 0, or comedi_command() will fail. For input subdevices, sample values are read using the function read(). For output subdevices, sample values are written using the function write().
If sucessful, 0 is returned, otherwise -1.