{
    Channel *chanPtr;		/* The channel to create the handler for. */
    ChannelState *statePtr;	/* State info for channel */
    Tcl_Channel chan;		/* The opaque type for the channel. */
    const char *chanName;
    int modeIndex;		/* Index of mode argument. */
    int mask;
    static const char *const modeOptions[] = {"readable", "writable", "exception", NULL};
    static const int maskArray[] = {TCL_READABLE, TCL_WRITABLE, TCL_EXCEPTION };

    if ((objc != 3) && (objc != 4)) {
	Tcl_WrongNumArgs(interp, 1, objv, "channelId event ?script?");
	return TCL_ERROR;
    }
    if (Tcl_GetIndexFromObj(interp, objv[2], modeOptions, "event name", 0,
	    &modeIndex) != TCL_OK) {
	return TCL_ERROR;
    }
    mask = maskArray[modeIndex];

    chanName = TclGetString(objv[1]);
    chan = Tcl_GetChannel(interp, chanName, NULL);
    if (chan == NULL) {
	return TCL_ERROR;
    }
    chanPtr = (Channel *) chan;
    statePtr = chanPtr->state;
    if ( ((statePtr->flags | TCL_EXCEPTION) & mask) == 0) {
	Tcl_SetObjResult(interp, Tcl_ObjPrintf("channel is not %s",
		(mask == TCL_READABLE) ? "readable" : "writable"));
	return TCL_ERROR;
    }

    /*
     * If we are supposed to return the script, do so.

    chan event gorp readable
} -returnCodes error -result {can not find channel named "gorp"}
test chan-io-41.4 {Tcl_FileeventCmd: errors} -constraints fileevent -body {
    chan event gorp writable
} -returnCodes error -result {can not find channel named "gorp"}
test chan-io-41.5 {Tcl_FileeventCmd: errors} -constraints fileevent -body {
    chan event gorp who-knows
} -returnCodes error -result {bad event name "who-knows": must be readable, writable, or exception}

#
# Test chan event on a file
#

set path(foo) [makeFile {} foo]
set f [open $path(foo) w+]

    list [catch {fileevent gorp readable} msg] $msg
} {1 {can not find channel named "gorp"}}
test io-41.4 {Tcl_FileeventCmd: errors} {fileevent} {
    list [catch {fileevent gorp writable} msg] $msg
} {1 {can not find channel named "gorp"}}
test io-41.5 {Tcl_FileeventCmd: errors} {fileevent} {
    list [catch {fileevent gorp who-knows} msg] $msg
} {1 {bad event name "who-knows": must be readable, writable, or exception}}

#
# Test fileevent on a file
#

set path(foo) [makeFile {} foo]
set f [open $path(foo) w+]

	int isNew)
{
    struct epoll_event newEvent;
    struct PlatformEventData *newPedPtr;
    struct stat fdStat;

    newEvent.events = 0;
    if (filePtr->mask & TCL_EXCEPTION) {
	newEvent.events |= EPOLLERR;
    }
    if (filePtr->mask & TCL_READABLE) {
	newEvent.events |= EPOLLIN;
    }
    if (filePtr->mask & TCL_WRITABLE) {
	newEvent.events |= EPOLLOUT;
    }
    if (isNew) {
        newPedPtr = ckalloc(sizeof(*newPedPtr));
        newPedPtr->filePtr = filePtr;
        newPedPtr->tsdPtr = tsdPtr;
	filePtr->pedPtr = newPedPtr;
    }
    newEvent.data.ptr = filePtr->pedPtr;

    /*
     * N.B.	As discussed in Tcl_WaitForEvent(), epoll(7) does not sup-
     *		port regular files (S_IFREG.) Therefore, filePtr is in these
     *		cases simply added or deleted from the list of FileHandlers
     *		associated with regular files belonging to tsdPtr.
     */
    
    if (newEvent.events & EPOLLERR) {
	/* if exceptions are requested, ignore file type */
    } else if (fstat(filePtr->fd, &fdStat) == -1) {
	Tcl_Panic("fstat: %s", strerror(errno));
    } else if ((fdStat.st_mode & S_IFMT) == S_IFREG) {
	switch (op) {
	case EPOLL_CTL_ADD:
	    if (isNew) {
		LIST_INSERT_HEAD(&tsdPtr->firstReadyFileHandlerPtr, filePtr, readyNode);
	    }
	    break;
	case EPOLL_CTL_DEL:
	    LIST_REMOVE(filePtr, readyNode);
	    break;
	}
	return;
   }
   if (epoll_ctl(tsdPtr->eventsFd, op, filePtr->fd, &newEvent) == -1) {
	Tcl_Panic("epoll_ctl: %s", strerror(errno));
   }
}

/*
 *----------------------------------------------------------------------
 *