Javascript exec() - a generic function that exec's and returns stdout, stderr

Question

I'm super new to JS and am struggling with a very basic task as I familiarize myself with it. I want to create a simple run(cmd) function that would receive a string with a command, and return an object containing stderr and stdout.

From what I found, I need to use exec or spawn, but I'm having trouble turning the examples online into a returning function:

const { exec } = require("child_process");

let run(cmd) = exec(cmd, (error, stdout, stderr) => {
    ret = {
        out: "",
        err: "",
        msg: ""
    }
    if (error) {
        ret.msg = error.message;
    }
    if (stderr) {
        ret.err = stderr;
    }
    ret.out = stdout;
    return ret;
});


out = run("ls -al");
console.log(out);

This doesn't work and I'm probably making mistakes on multiple levels here

UPDATE: The snippet I posted doesn't work, no outputs, just errors. I posted it because it is very simple and straightforward in terms of showing what I want to achieve. If I need to drop exec() for something else - I'm happy to hear suggestions.

Answer 1

exec() is a callback-based function and there is no way to do what you are doing without promisifying exec() or using a callback. You are returning from a function of it's own.

This is not even correct syntax for a function. You probably want to do something like this:

let run = (cmd, callback) => {
    exec(cmd, (e, so, se) => {
      // do stuff with the e, so, and se
      callback(e, so, se);
    });
};

run('ls', (e, so, se) => {
  // at this point you might just as well use exec()
});