func (e *Editor) Write(start, end int, cmd rune, text string) {
    args := strings.Split(text, " ")

    if len(args) > 1 {
        e.filename = args[0]
    }

e.filename = args[1]

func (e *Editor) isModified() bool {
    if e.modified {
        e.Error("warning: file modified")
        e.modified = false
        return true
    } else {
        return false
    }
}

    if len(text) == 0 {
        e.Error("invalid address")
        return 0, 0, ""
    }

    if len(text) == 0 {
	  if (e.line + 1 >= e.buffer.Len()) {
              e.Error("invalid address")
              return 0, 0, ""
	  } else {
              return e.line+1, e.line+1, "p"
	  }
    }