Tcl_Obj *toPtr,		/*
				 * NULL or the pathname of a file to link to.
				 */
    int linkAction)		/* Action to perform. */
{
    const Tcl_Filesystem *fsPtr = Tcl_FSGetFileSystemForPath(pathPtr);

    if (fsPtr != NULL && fsPtr->linkProc != NULL) {
	return fsPtr->linkProc(pathPtr, toPtr, linkAction);
    if (fsPtr) {
	if (fsPtr->linkProc == NULL) {
	    Tcl_SetErrno(ENOTSUP);
	    return NULL;
	} else {
	    return fsPtr->linkProc(pathPtr, toPtr, linkAction);
	}
    }

    /*
     * If S_IFLNK isn't defined the machine doesn't support symbolic links, so
     * the file can't possibly be a symbolic link. Generate an EINVAL error,
     * which is what happens on machines that do support symbolic links when
     * readlink is called for a file that isn't a symbolic link.