... comedi_errno -- number of last Comedilib error . ... int comedi_errno (void ); . When a Comedilib function fails, it usually returns -1 or NULL, depending on the return type. An internal library variable stores an error number, which can be retrieved with comedi_errno(). This error number can be converted to a human-readable form by the functions comedi_perror() and comedi_strerror(). ... The function comedi_errno() returns an integer describing the most recent comedilib error. ...