3 files changed, 35 insertions, 0 deletions
diff --git a/cli/js/deno_unstable.ts b/cli/js/deno_unstable.ts
index d8624c675..967eafdcd 100644
--- a/cli/js/deno_unstable.ts
+++ b/cli/js/deno_unstable.ts
@@ -4,6 +4,7 @@
 
 export { umask } from "./ops/fs/umask.ts";
 export { linkSync, link } from "./ops/fs/link.ts";
+export { fsyncSync, fsync } from "./ops/fs/sync.ts";
 export { symlinkSync, symlink } from "./ops/fs/symlink.ts";
 export { loadavg, osRelease, hostname } from "./ops/os.ts";
 export { openPlugin } from "./ops/plugins.ts";
diff --git a/cli/js/lib.deno.unstable.d.ts b/cli/js/lib.deno.unstable.d.ts
index 3339bfbac..daecf6604 100644
--- a/cli/js/lib.deno.unstable.d.ts
+++ b/cli/js/lib.deno.unstable.d.ts
@@ -1118,4 +1118,28 @@ declare namespace Deno {
    * ```
    */
   export function ftruncate(rid: number, len?: number): Promise<void>;
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   * Synchronously flushes any pending data and metadata operations of the given file stream to disk.
+   *  ```ts
+   * const file = Deno.openSync("my_file.txt", { read: true, write: true, create: true });
+   * Deno.writeSync(file.rid, new TextEncoder().encode("Hello World"));
+   * Deno.ftruncateSync(file.rid, 1);
+   * Deno.fsyncSync(file.rid);
+   * console.log(new TextDecoder().decode(Deno.readFileSync("my_file.txt"))); // H
+   * ```
+   */
+  export function fsyncSync(rid: number): void;
+
+  /** **UNSTABLE**: New API, yet to be vetted.
+   * Flushes any pending data and metadata operations of the given file stream to disk.
+   *  ```ts
+   * const file = await Deno.open("my_file.txt", { read: true, write: true, create: true });
+   * await Deno.write(file.rid, new TextEncoder().encode("Hello World"));
+   * await Deno.ftruncate(file.rid, 1);
+   * await Deno.fsync(file.rid);
+   * console.log(new TextDecoder().decode(await Deno.readFile("my_file.txt"))); // H
+   * ```
+   */
+  export function fsync(rid: number): Promise<void>;
 }
diff --git a/cli/js/ops/fs/sync.ts b/cli/js/ops/fs/sync.ts
new file mode 100644
index 000000000..5d5de7242
--- /dev/null
+++ b/cli/js/ops/fs/sync.ts
@@ -0,0 +1,10 @@
+// Copyright 2018-2020 the Deno authors. All rights reserved. MIT license.
+import { sendSync, sendAsync } from "../dispatch_json.ts";
+
+export function fsyncSync(rid: number): void {
+  sendSync("op_fsync", { rid });
+}
+
+export async function fsync(rid: number): Promise<void> {
+  await sendAsync("op_fsync", { rid });
+}