how to get file descriptor of process.{stdin,stdout,stderr}

[ORESoftware]

On Node.js 8+, is there a way to get file descriptors for process.stdin, process.stdout, process.stderr in the node.js runtime?

[addaleax]

Is process.stdin.fd, process.stdout.fd, process.stderr.fd what you’re looking for? They do have fixed values, i.e. 0, 1 and 2, unless you are running code inside a Worker (in which case they are not associated with fds) or the streams have been overwritten with other objects.

[ORESoftware]

that should do, i think i had this same problem before, typescript typings didnt mention the fd's

[gireeshpunathil]

closing as answered

[ORESoftware]

anyone know how this can be accomplished given a file descriptor perhaps in a Node.js process?
https://unix.stackexchange.com/questions/576954/discover-what-file-stdout-is-being-written-to

[martian17]

process.stdin.fd seems to induce EAGAIN error when passed as an argument to fs.readSync.
When passing a literal 0 no error is thrown.
If this is a bug I'll file an issue.
Here is an example code

const fs = require("fs");

const getchar = function(){
    const buffer = Buffer.alloc(1);
    fs.readSync(process.stdin.fd/*0*/, buffer, 0, 1);
    return buffer[0];
};

const readline = function(pmt){
    process.stdout.write(pmt);
    let c;
    const buff = [];
    while((c = getchar()) !== '\n'.charCodeAt(0)){
        buff.push(c);
    }
    return Buffer.from(buff).toString("utf8");
}

const age = readline("your age: ");
console.log(`You are ${age} years old`);
const name = readline("your name: ");
console.log(`Your name is ${name}`);