feat: add Deno.osName() (#5714)

cli/js/deno.ts

@@ -53,7 +53,7 @@ export {
 export { metrics, Metrics } from "./ops/runtime.ts";
 export { mkdirSync, mkdir, MkdirOptions } from "./ops/fs/mkdir.ts";
 export { connect, listen, Listener, Conn } from "./net.ts";
-export { env, exit, execPath } from "./ops/os.ts";
+export { dir, env, exit, execPath, osName } from "./ops/os.ts";
 export { run, RunOptions, Process, ProcessStatus } from "./process.ts";
 export { DirEntry, readDirSync, readDir } from "./ops/fs/read_dir.ts";
 export { readFileSync, readFile } from "./read_file.ts";

cli/js/lib.deno.unstable.d.ts

@@ -32,6 +32,18 @@ declare namespace Deno {
    * Requires `allow-read` and `allow-write` permissions. */
   export function linkSync(oldpath: string, newpath: string): void;
 
+  /**
+   * Returns the os name.
+   *
+   * ```ts
+   * console.log(Deno.osName());  // e.g. "Linux"
+   * ```
+   *
+   */
+
+  export function osName(): string;
+
+  /** Creates `newpath` as a hard link to `oldpath`.
   /** **UNSTABLE**: This API needs a security review.
    *
    * Creates `newpath` as a hard link to `oldpath`.

cli/js/ops/os.ts

@@ -72,3 +72,7 @@ export function dir(kind: DirKind): string | null {
 export function execPath(): string {
   return sendSync("op_exec_path");
 }
+
+export function osName(): string {
+  return sendSync("op_name");
+}