Deno nuggets: Download a file in Deno

This article is a part of the Deno nuggets series, where each article attempts to suggest a pointed solution to a specific question that can be read in less than a minute. There is no ordering of nuggets.

Problem

How to download a file in Deno?

~: curl https://upload.wikimedia.org/wikipedia/commons/8/84/Deno.svg -o /var/tmp/Deno.svg -s
~: ls -l /var/tmp/Deno.svg 
-rw-r--r--  1 mayankc  wheel  6281 May  5 22:33 /var/tmp/Deno.svg

Solution

With the introduction of ReadableStream & WritableStream interfaces for file handling, it has become very easy to download a file using a combination of two web standard APIs:

• fetch
• pipeTo

Here is the code of a function called downloadFile, that takes two inputs: Source URL of the file & destination path of the file. The function downloads the file at the given path. If the file doesn’t exist, it’s created. If a file exists, it’s overwritten.

Here is a simple test:

// app.ts
await downloadFile(
  "https://upload.wikimedia.org/wikipedia/commons/8/84/Deno.svg",
  "/var/tmp/Deno1.svg",
);
// --
~: deno run --allow-net --allow-write=/var/tmp/ --allow-read=/var/tmp/ app.ts
~: ls -ltr /var/tmp/Deno*
-rw-r--r--  1 mayankc  wheel  6281 May  5 22:33 /var/tmp/Deno.svg
-rw-r--r--  1 mayankc  wheel  6281 May  5 22:51 /var/tmp/Deno1.svg