public Channel openChannel(final int flags, int perm) throws IOException {
        final ModeFlags modeFlags = ModeFlags.createModeFlags(flags);
        if (posix.isNative() && !Platform.IS_WINDOWS) {
            int fd = posix.open(absolutePath(), modeFlags.getFlags(), perm);
            if (fd < 0) throwFromErrno(posix.errno());
            posix.fcntlInt(fd, Fcntl.F_SETFD, posix.fcntl(fd, Fcntl.F_GETFD) | FcntlLibrary.FD_CLOEXEC);
            return new NativeDeviceChannel(fd, true);
        }

        if (modeFlags.isCreate()) {
...
            // attempt to set the permissions, if we have been passed a POSIX instance,
            // perm is > 0, and only if the file was created in this call.
            if (fileCreated && posix != null) {
                perm = perm & ~PosixShim.umask(posix);

                if (perm > 0) posix.chmod(file.getPath(), perm);
            }

            return channel;
        }
...