What is the Deno equivalent of process.argv in Node.js?

Question

When working with NodeJS, I can pass the arguments to a Node script like this:

$ node node-server.js arg1 arg2=arg2-val arg3

And can get the arguments like so:

// print process.argv
process.argv.forEach(function (val, index, array) {
  console.log(index + ': ' + val);
});
//Output
0: node
1: /Users/umar/work/node/node-server.js
2: arg1 
3: arg2=arg2-val
4: arg3

How to get the command-line arguments in Deno?

Some experts suggested me to solve the problem by answers to the question

Headdress

Does this answer your question? How to pass command line arguments to Deno? – Bergeron

There aren't multiple ways to get command line arguments just one, Deno.args – Bergeron

Maybe, rename the title to "What is the Deno equivalent of process.argv in Node.js?". At least that was the way I interpreted your question with my answer. – Guglielmo

Great suggestion, Thanks! Done! – Headdress

Answer 1

Deno executable path ~ process.argv[0]:

Deno.execPath()

File URL of executed script ~ process.argv[1]:

Deno.mainModule

You can use path.fromFileUrl for conversions of URL to path string:

import { fromFileUrl } from "https://deno.land/[email protected]/path/mod.ts";
const modPath = fromFileUrl(import.meta.url)

Command-line arguments ~ process.argv.slice(2):

Deno.args

Example

deno run --allow-read test.ts -foo -bar=baz 42

Sample output (Windows):

Deno.execPath(): <scoop path>\apps\deno\current\deno.exe
import.meta.url: file:///C:/path/to/project/test.ts
  as path: C:\path\to\project\test.ts
Deno.args: [ "-foo", "-bar=baz", "42" ]

Guglielmo

This is wrong. You can't use import.meta.url for this, it contains the current file (like __filename in Node), not the main file, unless they happen to be the same. – Sacramentarian

Deno.mainModule is now stable. See comparison with import.meta.url. – Sacramentarian

@Sacramentarian huh, this is exactly, what I have written? "// put this in your main file to get its full path" – Guglielmo

ok but it's under a heading File URL of executed script ~ process.argv[1] and introduced as an alternative to Deno.mainModule in that context. Anyway as Deno.mainModule is long stable now, it can be edited – Sacramentarian

Answer 2

To get your script’s CLI arguments in Deno, just use Deno.args:

> deno run ./code.ts foo bar

console.log(Deno.args); // ['foo', 'bar']

---

If you need something identical to Node's process.argv for compatibility reasons, use the official 'node' shim:

import process from 'https://deno.land/[email protected]/node/process.ts'

console.log(process.argv); // ['/path/to/deno', '/path/to/code.ts', 'foo', 'bar']

---

For illustrative purposes, if you wanted to manually construct a process.argv-style array (without using the official 'node' shim) you could do this:

import { fromFileUrl } from "https://deno.land/[email protected]/path/mod.ts";

const argv = [
   Deno.execPath(),
   fromFileUrl(Deno.mainModule),
   ...Deno.args,
]

console.log(argv); // ['/path/to/deno', '/path/to/code.ts', 'foo', 'bar']

Sacramentarian