@Override
    public Promise<Void> chmod(String path, String perms) {
        return adapter.toPromise(handler -> vertx.fileSystem().chmod(path, perms, handler));
    }
@ Override public Promise < Void > chmod ( String path , String perms ) { return adapter . toPromise ( handler -> vertx . fileSystem ( ) . chmod ( path , perms , handler ) ) ; }
Change the permissions on the file represented by {@code path} to {@code perms}, asynchronously.
<p>
The permission String takes the form rwxr-x--- as
specified <a href="http://download.oracle.com/javase/7/docs/api/java/nio/file/attribute/PosixFilePermissions.html">here</a>.

@param path  the path to the file
@param perms the permissions string
@return a promise for completion