diff --git a/mod.ts b/mod.ts
index f95b385..f79446d 100644
--- a/mod.ts
+++ b/mod.ts
@@ -1,88 +1,98 @@
 // Copyright (c) 2019 Rafał Pocztarski. All rights reserved.
 // MIT License (Expat). See: https://github.com/rsp/deno-clipboard
 
+type OperatingSystem = typeof Deno.build.os
+
 type Dispatch = {
-  [key in Deno.OperatingSystem]: Clipboard;
-};
+  [key in OperatingSystem]: Clipboard
+}
 
-const encoder = new TextEncoder();
-const decoder = new TextDecoder();
+const encoder = new TextEncoder()
+const decoder = new TextDecoder()
 
-export const encode = (x: string) => encoder.encode(x);
-export const decode = (x: Uint8Array) => decoder.decode(x);
+export const encode = (x: string) => encoder.encode(x)
+export const decode = (x: Uint8Array) => decoder.decode(x)
 
 const opt: Deno.RunOptions = {
-  args: [],
-  stdin: 'piped',
-  stdout: 'piped',
-  stderr: 'piped',
-};
+  cmd: [],
+  stdin: "piped",
+  stdout: "piped",
+  stderr: "piped",
+}
 
-async function read(args: string[]): Promise<string> {
-  const p = Deno.run({ ...opt, args });
-  return decode(await p.output());
+async function read(cmd: string[]): Promise<string> {
+  const p = Deno.run({ ...opt, cmd })
+  return decode(await p.output())
 }
 
-async function write(args: string[], data: string): Promise<void> {
-  const p = Deno.run({ ...opt, args });
-  await p.stdin.write(encode(data));
-  p.stdin.close();
-  await p.status();
+async function write(cmd: string[], data: string): Promise<void> {
+  const p = Deno.run({ ...opt, cmd })
+  await p.stdin?.write(encode(data))
+  p.stdin?.close()
+  await p.status()
 }
 
 const linux: Clipboard = {
-  os: 'linux',
+  os: "linux",
   async readText() {
     // return read(['xclip', '-selection', 'clipboard', '-o']);
-    return read(['xsel', '-b', '-o']);
+    return read(["xsel", "-b", "-o"])
   },
   async writeText(data) {
     // return write(['xclip', '-selection', 'clipboard'], data);
-    return write(['xsel', '-b', '-i'], data);
+    return write(["xsel", "-b", "-i"], data)
   },
-};
+}
 
 const mac: Clipboard = {
-  os: 'mac',
+  os: "darwin",
   async readText() {
-    return read(['pbpaste']);
+    return read(["pbpaste"])
   },
   async writeText(data) {
-    return write(['pbcopy'], data);
+    return write(["pbcopy"], data)
   },
-};
+}
 
 const win: Clipboard = {
-  os: 'win',
+  os: "windows",
   async readText() {
-    const data = await read(['powershell', '-noprofile', '-command', 'Get-Clipboard']);
-    return data.replace(/\r/g, '').replace(/\n$/, '');
+    const data = await read([
+      "powershell",
+      "-noprofile",
+      "-command",
+      "Get-Clipboard",
+    ])
+    return data.replace(/\r/g, "").replace(/\n$/, "")
   },
   async writeText(data) {
-    return write(['powershell', '-noprofile', '-command', '$input|Set-Clipboard'], data);
+    return write(
+      ["powershell", "-noprofile", "-command", "$input|Set-Clipboard"],
+      data,
+    )
   },
-};
+}
 
 const dispatch: Dispatch = {
   linux,
-  mac,
-  win,
-};
+  darwin: mac,
+  windows: win,
+}
 
 class Clipboard {
-  os: Deno.OperatingSystem;
-  constructor(os: Deno.OperatingSystem) {
+  os: OperatingSystem
+  constructor(os: OperatingSystem) {
     if (!dispatch[os]) {
-      throw new Error(`Clipboard: unsupported OS: ${os}`);
+      throw new Error(`Clipboard: unsupported OS: ${os}`)
     }
-    this.os = os;
+    this.os = os
   }
   async readText(): Promise<string> {
-    return dispatch[this.os].readText();
+    return dispatch[this.os].readText()
   }
   async writeText(data: string): Promise<void> {
-    return dispatch[this.os].writeText(data);
+    return dispatch[this.os].writeText(data)
   }
 }
 
-export const clipboard = new Clipboard(Deno.build.os);
+export const clipboard = new Clipboard(Deno.build.os)