int fd;
    ClientData data;

    if (objc != 4) {
	Tcl_WrongNumArgs(interp, 2, objv, "file readable|writable|both timeout");
	return TCL_ERROR;
    }
    channel = Tcl_GetChannel(interp, Tcl_GetString(objv[1]), (void *)NULL);
    channel = Tcl_GetChannel(interp, Tcl_GetString(objv[1]), NULL);
    if (channel == NULL) {
	return TCL_ERROR;
    }
    if (strcmp(Tcl_GetString(objv[2]), "readable") == 0) {
	mask = TCL_READABLE;
    } else if (strcmp(Tcl_GetString(objv[2]), "writable") == 0){
	mask = TCL_WRITABLE;