Create a persistent bash shell session in Node.js, know when commands finish, and read and modify sourced/exported variables

Question

Imagine this contrived scenario:

./main.sh

source ./config.sh
SOME_CONFIG="${SOME_CONFIG}bar"
./output.sh

./config.sh

export SOME_CONFIG='foo'

./output.sh

echo "Config is: ${SOME_CONFIG}"

I am trying to replace ./main.sh with a Node.js powered ./main.js WITHOUT replacing the other shell files. The exported ./config.sh functions/variables must also be fully available to ./output.sh

Here is a NON working ./main.js. I have written this for the sole purpose to explain what I want the final code to look like:

const terminal = require('child_process').spawn('bash')

terminal.stdin.write('source ./config.sh\n')
process.env.SOME_CONFIG = `${process.env.SOME_CONFIG}bar` // this must be done in JS
terminal.stdin.write('./output.sh\n') // this must be able to access all exported functions/variables in config.sh, including the JS modified SOME_CONFIG

How can I achieve this? Ideally if there's a library that can do this I'd prefer that.

It would help if you edit the question to add some more information on why the environment needs to be edited from JS. — root, Mar 07 '21 at 05:25
The real reason is I want to move away from shell scripts, at least those in my control. I want to replace them with JS. The contrived example demonstrates the problem I have where I own *. /main.sh* but not the other 2 files. I also don't understand how your linked stack exchange could help here. — Molten Ice, Mar 07 '21 at 09:45
A process (node.js) can't change environment variables of another running process (bash). I suspect it's not a real requirement, which is why you should provide more context. — root, Mar 07 '21 at 22:18

score 1 · Answer 1 · answered Mar 07 '21 at 23:16

While this doesn't fully answer my question, it solves the contrived problem I had at hand and could help others if need be.

In general, if bash scripts communicate with each other via environment variables (eg. using export/source), this will allow you to start moving bash code to Node.js.

./main.js

const child_process = require("child_process");
const os = require("os");

// Source config.sh and print the environment variables including SOME_CONFIG
const sourcedConfig = child_process
  .execSync(". ./config.sh > /dev/null 2>&1 && env")
  .toString();

// Convert ALL sourced environment variables into an object
const sourcedEnvVars = sourcedConfig
  .split(os.EOL)
  .map((line) => ({
    env: `${line.substr(0, line.indexOf("="))}`,
    val: `${line.substr(line.indexOf("=") + 1)}`,
  }))
  .reduce((envVarObject, envVarEntry) => {
    envVarObject[envVarEntry.env] = envVarEntry.val;
    return envVarObject;
  }, {});

// Make changes
sourcedEnvVars["SOME_CONFIG"] = `${sourcedEnvVars["SOME_CONFIG"]}bar`;

// Run output.sh and pass in the environment variables we got from the previous command
child_process.execSync("./output.sh", {
  env: sourcedEnvVars,
  stdio: "inherit",
});

Maybe actually there is not a way to get it working like a persistent sh/bash session to send commands, but one can simply just create a .sh file and then run it through nodejs child_process.exec so it CAN have sourcing or anything else that needs to be did in a single sh/bash session, will be harder to implement proper error handling and so you have knowledge about sh/bash coding, but it works. +1 — Máxima Alekz, Jun 01 '22 at 18:24

Create a persistent bash shell session in Node.js, know when commands finish, and read and modify sourced/exported variables

1 Answers1