Use channel “chnl” to open file “file” in append mode with access mode “access” and share mode “shrmod”

      valid channels:      0 - 7 [0 is used for script questionnaires]  
      valid access modes:  O_RD, O_WR, O_RW [should use O_RW]  
      valid share modes:   S_DN, S_DR, S_DW, S_DB  

See also: FOpen, FClose, FCreate