Read and write files

• Deno’s runtime API provides the Deno.readTextFile and asynchronous functions for reading and writing entire text files.
• Use and --allow-write permissions to gain access to the file system.

As highlighted in the Fetch Data example Deno restricts access to Input / Output by default for security reasons. Therefore when interacting with the filesystem the --allow-read and --allow-write flags must be used with the deno run command.

The Deno runtime API makes it possible to read text files via the method, it just requires a path string or URL object. The method returns a promise which provides access to the file’s text data.

Command: deno run --allow-read read.ts

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The Deno runtime API allows developers to write text to files via the Deno.writeTextFile() method. It just requires a file path and text string. The method returns a promise which resolves when the file was successfully written.

To run the command the --allow-write flag must be supplied to the deno run command.

Command:

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By combining Deno.writeTextFile and JSON.stringify you can easially write serialized JSON objects to a file. This example uses synchronous Deno.writeTextFileSync, but this can also be done asynchronously using await Deno.writeTextFile.

To execute the code the command needs the write flag.

Command: deno run --allow-write write.ts

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