return a string from an async nodejs function called in bash

Question

i'm calling an async nodejs function that uses prompts(https://www.npmjs.com/package/prompts) basically, the user is presented options and after they select one, i want the selection outputted to a variable in bash. I cannot get this to work. it either hangs, or outputs everything since prompts is a user interface that uses stdout

//nodefunc.js

async run() {
  await blahhhh;
  return result; // text string
}

console.log(run());

// bash

x=$(node nodefunc.js)

echo $x

What is output of node nodefunc.js and what you want in variable in X — Digvijay S
– Digvijay S, Commented Aug 31, 2020 at 4:26
try executing code in verbose mode. tldp.org/LDP/Bash-Beginners-Guide/html/sect_02_03.html — Digvijay S
– Digvijay S, Commented Aug 31, 2020 at 4:49

FishSaidNo · Accepted Answer · 2020-08-31 06:11:56Z

1

Unless you can ensure nothing else in the node script will print to stdout, you will need a different approach.

I'd suggest having the node script write to a temporary file, and have the bash script read the output from there. Something like this perhaps:

const fs = require('fs');
const outputString = 'I am output';
fs.writeFileSync('/tmp/node_output.txt', outputString);

node nodefunc.js

# Assuming the node script ran succesfully, read the output file
x=$(</tmp/node_output.txt)
echo "$x"

# Optionally, cleanup the tmp file
rm /tmp/node_output.txt

answered Aug 31, 2020 at 6:11

FishSaidNo

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1 Comment

tricon Over a year ago

Am I wrong or is everything here happening synchronously? The question was about returning a value from an async nodejs function and echoing that in bash, no?

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