Call execv (works similar for execvp, execve) on Node 20

node-execv.ts

import ref from "ref-napi";
import ffi from "ffi-napi";
import ref_array_di from "ref-array-di";

const ArrayType = ref_array_di(ref);

const StringArray = ArrayType("string");

// from fcntl.h
const F_GETFD = 1; /* get close_on_exec */
const F_SETFD = 2; /* set/clear close_on_exec */
const FD_CLOEXEC = 1; /* actually anything with low bit set goes */

export function execv(path: string, args: string[]): number | never {
  const current = ffi.Library(null, {
    execv: ["int", ["string", StringArray]],
    fcntl: ["int", ["int", "int", "int"]],
  });

  function dontCloseOnExit(fd: number) {
    let flags = current.fcntl(fd, F_GETFD, 0);
    if (flags < 0) return flags;
    flags &= ~FD_CLOEXEC; //clear FD_CLOEXEC bit
    return current.fcntl(fd, F_SETFD, flags);
  }

  const argsArray = new StringArray(args.length + 1);
  for (let i = 0; i < args.length; i++) {
    argsArray[i] = args[i];
  }
  argsArray[args.length] = null;

  dontCloseOnExit(process.stdin.fd);
  dontCloseOnExit(process.stdout.fd);
  dontCloseOnExit(process.stderr.fd);

  return current.execv(path, argsArray);
}

args must contain arg0.

Re-execing the current process might look like:

execv(process.execPath, [process.argv0, ...process.execArgv, ...process.argv.slice(1)])

This gist was inspired by the existing answers to this StackOverflow question by user1629060 (using ffi) and oleksii-rudenko (removing the "exit on close" flag from the streams).

I have also posted it as an answer here: https://stackoverflow.com/a/77774287/1479482