File System Access

Deno Native API

;; Read a text file
(bind content (await (Deno:read-text-file "config.json")))

;; Write a text file
(await (Deno:write-text-file "output.txt" content))

;; Read directory entries
(for-await-of entry (Deno:read-dir "src")
  (console:log entry:name entry:is-file))

Deno’s API is simple — read-text-file is always UTF-8, no encoding option needed.

Node.js Compatibility

(import "node:fs/promises" (read-file write-file mkdir))

(bind data (await (read-file "config.json" (obj :encoding "utf-8"))))
(await (write-file "output.txt" data))
(await (mkdir "dist" (obj :recursive true)))

Both work in Deno. The Deno native API is simpler; the node:fs API is compatible with Node.js documentation and code.

Permissions

Deno requires explicit permission flags for file access:

deno run --allow-read=config.json --allow-write=output.txt app.js

Without the flags, file operations throw a PermissionError. This is a feature — explicit permissions prevent accidental file system access from untrusted code. You can grant broad access (--allow-read) or narrow it to specific paths (--allow-read=src,config.json).

Keyboard shortcuts

Lykn