spawnSync shell command, error cut: -: Bad file descriptor

[Tatsujinichi]

Here is my stackoverflow link to the question. https://stackoverflow.com/questions/58796378/spawnsync-for-shell-commands

I wonder if this may be a bug?

const { spawnSync } = require('child_process');
const fs = require('fs-extra');

function trimFile() {
    let rfd;
    let wfd;
    try {
        rfd = fs.openSync('filelist.txt', 'r');
        wfd = fs.openSync('filesonly.txt', 'w');
        spawnSync('cut -d" " -f1', { stdio: [wfd, rfd, 'inherit'] });
    }
    finally {
        fs.closeSync(rfd);
        fs.closeSync(wfd);
    }
}

• Version:
  11.8.0
• Platform:
  Ubuntu 18.04
  Linux computerName 4.15.0-66-generic Deprecate domains node#75-Ubuntu SMP Tue Oct 1 05:24:09 UTC 2019 x86_64 x86_64 x86_64 GNU/Linux
• Subsystem:
  child_process

[Trott]

It won't fix your problem, but FYI Node.js 11 is unsupported. Please consider moving to Node.js 12 or 13 instead.

[Trott]

You need to separate your commands from the arguments in your spawnSync() invocation:

        spawnSync('cut', ['-d', " ", '-f1'], { stdio: [wfd, rfd, 'inherit'] });

Otherwise, it treats the command as cut -d" " -f1 which you might think will work but there is unlikely to be a command cut -d" " -f1 on your system. It's cut with the other stuff as arguments.

[Trott]

(It still won't do what you want, I don't think, but that's one thing that needs fixing.)

[Tatsujinichi]

Oh I see. Is this correct with shell: true?

[github-actions]

There has been no activity on this issue for 3 years and it may no longer be relevant. It will be closed 1 month after the last non-automated comment.

[andres-lowrie]

so this may still be an issue perhaps?

With latest lts version

node --version
v18.14.0

Given I have 2 files in some directory

touch err out

and write a script like this

const { spawnSync } = require('child_process')
const fs = require('fs')

const out = fs.openSync('./out')
const err = fs.openSync('./err')

spawnSync('echo', ['hello'], { stdio: ['pipe', out, err]})

the script runs without errors but the file used for stdout is empty

ls -l
-rw-r--r--   1 andreslowrie  staff     0 Feb 10 16:37 err
-rw-r--r--   1 andreslowrie  staff   264 Feb 10 16:37 index.js
-rw-r--r--   1 andreslowrie  staff     0 Feb 10 16:37 out

Where I'm expecting there would be hello in the file out

---

If I instead use fs.createWriteStream

const { spawnSync } = require('child_process')
const fs = require('fs')

//const out = fs.openSync('./out')
//const err = fs.openSync('./err')
//

const out = fs.createWriteStream('./out')
const err = fs.createWriteStream('./err')

out.on('open', () => {
  err.on('open', () => {
    spawnSync('echo', ['hello'], { stdio: ['pipe', out, err] })
  })
})

it in fact writes to the output

ls -l
-rw-r--r--   1 andreslowrie  staff     0 Feb 10 16:40 err
-rw-r--r--   1 andreslowrie  staff   352 Feb 10 16:40 index.js
-rw-r--r--   1 andreslowrie  staff     6 Feb 10 16:40 out
cat out
hello

---

This is probably a user error in reading the docs, but shouldn't the first method work the same way the second method does?, given that the script passes open fd numbers to the stdio option ?

[github-actions]

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[github-actions]

It seems there has been no activity on this issue for a while, and it is being closed. If you believe this issue should remain open, please leave a comment.
If you need further assistance or have questions, you can also search for similar issues on Stack Overflow.
Make sure to look at the README file for the most updated links.