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import { exists } from "https://deno.land/std@0.147.0/fs/mod.ts";import * as path from "https://deno.land/std@0.147.0/path/mod.ts";
export default async function which(command: string): Promise<string | null> {  const pathEnv = Deno.env.get("PATH") ?? "";  const pathExtEnv = Deno.env.get("PATHEXT");  const paths = pathEnv.split(path.delimiter);  const pathExts = pathExtEnv    ? pathExtEnv.split(path.delimiter).concat("")    : [""];  for (const dir of paths) {    for (const ext of pathExts) {      const absolutePath = path.resolve(dir, command + ext);      if (await exists(absolutePath)) return absolutePath;    }  }  return null;}