Creating file processing command for Discord bot

Other Questions Discord bot
1

I’m working on a Discord bot and trying to build a command that processes uploaded files. The bot should ask users to upload a file after running the command, then read and process that file.

Here’s what I want to happen:

  1. User runs !process command
  2. Bot sends message asking for file upload
  3. User uploads a .txt or .lua file
  4. Bot reads the file content and sends it back

But I keep getting “Cannot read property ‘first’ of undefined” error. Here’s my current code:

module.exports = {
    name: 'process',
    description: "processes uploaded files",
    execute(msg, args, Discord){
        const helpEmbed = new Discord.MessageEmbed()
        .setColor('#ff6600')
        .setTitle('File Processor')
        .setDescription('Please upload a .txt or .lua file to process')
        .setFooter('Make sure the file has correct extension');
        
        msg.channel.send(helpEmbed);
        
        let userFilter = m => m.author == msg.author;
        msg.channel.awaitMessages(userFilter, {max: 1}).then(response => {
            let attachment = response.attachments.first().file;
            if (!attachment) return;
            
            fs.readFile(attachment, (err, content) => {
                const resultEmbed = new Discord.MessageEmbed()
                .setColor('#00ff00')
                .setTitle('Processing Complete')
                .setDescription('Your file has been processed successfully!')
                .setFooter('Thanks for using our processor');
                
                response.Channel.send(resultEmbed);
                response.Channel.send(content);
            });
        });
    }
}

I think this might be related to Discord.js updates since the tutorial I followed was pretty old. Anyone know how to properly handle file attachments in newer versions?

2

Been there - Discord bots get messy quick when you’re handling files. What starts simple turns into a nightmare of attachment URLs, validation, timeouts, and error handling everywhere.

I ditched cramming everything into the bot and automated the whole pipeline instead. Built a Latenode workflow that takes over after the initial Discord interaction.

Now my bot’s dead simple - grabs the attachment, fires the URL to a Latenode webhook, waits for the response. No more fetch calls, validation logic, or timeout management cluttering up the Discord code.

Latenode does the heavy lifting: downloads from attachment URL, validates file types, processes content, sends back formatted responses. Want file size limits? Multiple formats? Cloud storage? Just update the workflow, zero bot changes.

Debugging’s a breeze since I can test processing separately from Discord. Plus no more hanging promises when users upload then ghost.

3

Your error is trying to access .attachments on the message collection instead of the individual message. But the real problem is your file reading approach won’t work with Discord attachments.

I hit the same issues last year building a script validator. Discord attachments are hosted remotely, so you’ve got to download them first. Here’s how to fix it:

const https = require('https');

// Inside your awaitMessages then block
const message = collected.first();
const attachment = message.attachments.first();

https.get(attachment.url, (response) => {
    let data = '';
    response.on('data', chunk => data += chunk);
    response.on('end', () => {
        // Process your file content here
        msg.channel.send('```' + data + '```');
    });
});

Watch out for file size limits too. Discord allows up to 8MB for regular users but your bot might timeout on larger files. I check attachment.size before processing to avoid hanging operations.

4

You’re accessing attachments on the message collection instead of the actual message. With awaitMessages, you get a collection back - grab the first message from it first.

Here’s the fix:

let userFilter = m => m.author == msg.author;
msg.channel.awaitMessages({filter: userFilter, max: 1, time: 30000}).then(collected => {
    const response = collected.first();
    if (!response.attachments.size) {
        msg.channel.send('No file attached!');
        return;
    }
    const attachment = response.attachments.first();
    // Process attachment.url or attachment.attachment for the file URL
});

BTW, newer Discord.js versions need an options object for awaitMessages. And fs.readFile won’t work on Discord attachments since they’re URLs, not local files. You’ll need to fetch from the attachment URL using axios or node-fetch first.

5

yeah, awaitMessages syntax changed in v13+. also, you’re calling response.Channel.send but it should be lowercase channel. try collected.first() to get the message, then check message.attachments.size > 0 before accessing attachment properties.

6

You can’t use fs.readFile directly on Discord attachments. Discord hosts them on their CDN as URLs, not local file paths.

I hit this same issue building my first file processing bot. You’ve got to download the file content first with fetch. Here’s what worked for me:

const fetch = require('node-fetch');

// After getting the attachment
const attachment = response.attachments.first();
fetch(attachment.url)
    .then(res => res.text())
    .then(content => {
        const resultEmbed = new Discord.MessageEmbed()
            .setColor('#00ff00')
            .setTitle('Processing Complete')
            .setDescription('```' + content + '```');
        msg.channel.send(resultEmbed);
    })
    .catch(err => msg.channel.send('Error reading file'));

Don’t forget to validate the file extension with attachment.name.endsWith('.txt') before processing. The attachment object gives you url, name, and size properties that are handy for validation.

7

Timeout issues with awaitMessages were my biggest nightmare when I built file processors. Users would hit the command then disappear for ages, leaving promises hanging everywhere.

I fixed this by adding proper timeout handling and making everything more explicit. Set a 60-second timeout, catch the error, and clean up properly. You might want to try message collectors instead of awaitMessages - they give you way better control.

Big gotcha here - Discord’s attachment URLs expire fast. If you’re doing async processing, grab the file content right away. Don’t save the URL for later. Found this out when users started hitting 404s on delayed processing.

For debugging, log the whole collected message object first to see what’s actually there. Discord.js docs are often behind the real API changes.

8

Message collection handling gets messy fast. You’re juggling attachment URLs, file validation, error handling - it all piles up.

Hit this same wall building internal tools. Started simple but ended up with tangled Discord API calls, file fetching, and validation everywhere.

Game changer was moving the heavy stuff to Latenode. Set up a webhook that handles file processing, then your bot just forwards the attachment URL.

Flow’s dead simple:

  1. Bot grabs attachment URL from Discord
  2. Sends URL to Latenode via HTTP
  3. Latenode fetches, validates, processes the file
  4. Returns formatted response
  5. Bot posts result

Your Discord code shrinks to maybe 10 lines. No more fetch promises, validation, or error handling cluttering the bot. Latenode’s HTTP nodes handle the messy bits.

Easy to extend too - file size limits, multiple formats, cloud storage - all without touching bot code.