Handle channel exceptions

Channel errors can be trapped with the WHENEVER ERROR exception handler:

MAIN
    DEFINE ch base.Channel
    DEFINE num INT, label CHAR(50)
    LET ch = base.Channel.create()
    --CALL ch.openFile("data.txt","w")
    WHENEVER ERROR CONTINUE
    CALL ch.write([num,label])
    IF status<0 THEN
        DISPLAY SFMT("Could not write to channel: status=%1",status)
    END IF
END MAIN

Or with a TRY/CATCH block:

MAIN
    DEFINE ch base.Channel
    DEFINE num INT, label CHAR(50)
    LET ch = base.Channel.create()
    --CALL ch.openFile("data.txt","w")
    TRY
        CALL ch.write([num,label])
    CATCH
        DISPLAY SFMT("Could not write to channel: status=%1",status)
    END TRY
END MAIN

Could not write to channel: status=-6344