Running bash script from Deno

Question

Let's say I've got this super useful and advanced bash script:

#!/usr/bin/env bash

echo What is your name?
read name
echo What is your age?
read age

When I try to run it from Deno with a simple script like this:

const process = Deno.run({
  cmd: [`./bash.sh`],
  stdin: "piped",
  stdout: "piped",
});

const decoder = new TextDecoder();

const output = await process.output()
const parsed = decoder.decode(output);

console.log(parsed);

It returns nothing, but if I simplify the Deno script to the first line of the bash script it returns the output just fine

const process = Deno.run({
  cmd: [`echo`, `What is your name?`],
  stdin: "piped",
  stdout: "piped",
});

const decoder = new TextDecoder();

const output = await process.output()
const parsed = decoder.decode(output);

console.log(parsed);

Why is this? I'd assume since the start of the bash file and the single line command both start with echo it would return the same result twice

Answer 1

Version 1.5 of denoadded the prompt function which allows you to completely remove the need for shelling out to a different program and handling inter-process communication via stdin/stdout.

let name: string | null = null;
let age: string | null = null;

while (name === null) {
  name = prompt("What is your name?");
}

while (age === null) {
  age = prompt("What is your age?");
}

console.log(`you are ${name}, ${age}yo`);

Answer 2

Your code is telling Deno to set up the subprocess to expect piped stdin -- but never providing it any content on stdin, Consequently, it hangs in the very first read .

If we take that out (letting stdin be passed through from the parent process), and do in fact answer the two prompts on the parent process's stdin, everything works perfectly:

deno run --allow-run run-bash.js <<'EOF'
A Nony Mouse
3
EOF

...with run-bash.js containing:

const process = Deno.run({
  cmd: [`./bash.sh`],
  stdout: "piped",
});

const decoder = new TextDecoder();

const output = await process.output()
const parsed = decoder.decode(output);

console.log(parsed);

...and your bash.sh unchanged. output thus captures the two prompts ( What is your name? and What is your age? ), and forwards them to the javascript interpreter's stdout as-requested.

Answer 3

You have to call bash to call your script ( of course with --allow-run option ) like:

const process = Deno.run({
  cmd: ["bash","bash.sh"],
  stdin: "piped",
  stdout: "piped",
});

const decoder = new TextDecoder();

const output = await process.output()
const parsed = decoder.decode(output);

console.log(parsed);