Function getValidStdio

lib/internal/child_process.js:1008–1107

(stdio, sync)

const nop = FunctionPrototype;

function getValidStdio(stdio, sync) {
  let ipc;
  let ipcFd;

  // Replace shortcut with an array
  if (typeof stdio === 'string') {
    stdio = stdioStringToArray(stdio);
  } else if (!ArrayIsArray(stdio)) {
    throw new ERR_INVALID_ARG_VALUE('stdio', stdio);
  }

  // At least 3 stdio will be created
  // Don't concat() a new Array() because it would be sparse, and
  // stdio.reduce() would skip the sparse elements of stdio.
  // See https://stackoverflow.com/a/5501711/3561
  while (stdio.length < 3) ArrayPrototypePush(stdio, undefined);

  // Translate stdio into C++-readable form
  // (i.e. PipeWraps or fds)
  stdio = ArrayPrototypeReduce(stdio, (acc, stdio, i) => {
    function cleanup() {
      for (let i = 0; i < acc.length; i++) {
        if ((acc[i].type === 'pipe' || acc[i].type === 'ipc') && acc[i].handle)
          acc[i].handle.close();
      }
    }

    // Defaults
    stdio ??= i < 3 ? 'pipe' : 'ignore';

    if (stdio === 'ignore') {
      ArrayPrototypePush(acc, { type: 'ignore' });
    } else if (stdio === 'pipe' || stdio === 'overlapped' ||
               (typeof stdio === 'number' && stdio < 0)) {
      const a = {
        type: stdio === 'overlapped' ? 'overlapped' : 'pipe',
        readable: i === 0,
        writable: i !== 0,
      };

      if (!sync)
        a.handle = new Pipe(PipeConstants.SOCKET);

      ArrayPrototypePush(acc, a);
    } else if (stdio === 'ipc') {
      if (sync || ipc !== undefined) {
        // Cleanup previously created pipes
        cleanup();
        if (!sync)
          throw new ERR_IPC_ONE_PIPE();
        else
          throw new ERR_IPC_SYNC_FORK();
      }

      ipc = new Pipe(PipeConstants.IPC);
      ipcFd = i;

      ArrayPrototypePush(acc, {