Write to stdout
console.log is fine for debugging, but command line tools often need precise control over standard output: no forced newline, raw bytes, or piping a whole stream. This example shows each approach.
Deno.stdout accepts raw bytes. Unlike console.log, nothing is appended, so the two writes below land on the same line.
const encoder = new TextEncoder();
await Deno.stdout.write(encoder.encode("Hello, "));
await Deno.stdout.write(encoder.encode("World!\n")); // Hello, World!A single low-level write call may write fewer bytes than given. The web standard writer on Deno.stdout guarantees the whole chunk is written. Release the lock afterwards so other code can use stdout again.
const writer = Deno.stdout.writable.getWriter();
await writer.write(encoder.encode("All bytes written\n"));
writer.releaseLock();There is a synchronous variant of the low-level write as well.
Deno.stdout.writeSync(encoder.encode("Sync write\n"));A readable stream can be piped to stdout directly. Prevent the pipe from closing stdout if the program continues.
const stream = ReadableStream.from(["Streamed to stdout\n"])
.pipeThrough(new TextEncoderStream());
await stream.pipeTo(Deno.stdout.writable, { preventClose: true });Code written for Node.js uses process.stdout, which works in Deno too and accepts strings directly.
import process from "node:process";
process.stdout.write("Via process.stdout\n");Errors and diagnostics belong on stderr instead, so they do not corrupt output that is being piped to another program.
await Deno.stderr.write(encoder.encode("A diagnostic message\n"));Run this example locally using the Deno CLI:
deno run https://docs.deno.com/examples/scripts/write_stdout.ts