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# Working with the filesystem in Node.js

You’ll commonly need to work with files in a workflow, for example: downloading content from some service to upload to another. This doc explains how to work with files in Pipedream workflows and provides some sample code for common operations.

# The `/tmp` directory

Within a workflow, you have full read-write access to the /tmp directory. You have 2GB of available space in /tmp to save any file.

# Managing `/tmp` across workflow runs

The /tmp directory is stored on the virtual machine that runs your workflow. We call this the execution environment (“EE”). More than one EE may be created to handle high-volume workflows. And EEs can be destroyed at any time (for example, after about 10 minutes of receiving no events). This means that you should not expect to have access to files across executions. At the same time, files may remain, so you should clean them up to make sure that doesn’t affect your workflow. Use the tmp-promise package (opens new window) to cleanup files after use, or delete the files manually.

# Reading a file from `/tmp`

This example uses step exports to return the contents of a test file saved in /tmp as a string:

import
 fs from
 "fs"
;

export
 default
 defineComponent
(
{
  async
 run
(
{
 steps,
 $ }
)
 {
    return
 (
await
 fs.
promises.
readFile
(
'/tmp/your-file'
)
)
.
toString
(
)
  }
}
)
;

# Writing a file to `/tmp`

Use the fs module (opens new window) to write data to /tmp:

import
 fs from
 "fs"
import
 {
 file }
 from
 'tmp-promise'

export
 default
 defineComponent
(
{
  async
 run
(
{
 steps,
 $ }
)
 {
    const
 {
 path,
 cleanup }
 =
 await
 file
(
)
;
    await
 fs.
promises.
appendFile
(
path,
 Buffer.
from
(
"hello, world"
)
)
    await
 cleanup
(
)
;
  }
}
)
;

# Listing files in `/tmp`

Return a list of the files saved in /tmp:

import
 fs from
 "fs"
;

export
 default
 defineComponent
(
{
  async
 run
(
{
 steps,
 $ }
)
 {
    return
 fs.
readdirSync
(
"/tmp"
)
;
  }
}
)
;

# Delete a file

import
 fs from
 "fs"
;

export
 default
 defineComponent
(
{
  async
 run
(
{
 steps,
 $ }
)
 {
    return
 await
 fs.
promises.
unlink
(
'/tmp/your-file'
)
;
  }
}
)
;

# Download a file to `/tmp`

See this example to learn how to download a file to /tmp.

# Upload a file from `/tmp`

See this example to learn how to upload a file from /tmp in an HTTP request.

# Download a file, uploading it in another `multipart/form-data` request

This workflow (opens new window) provides an example of how to download a file at a specified Download URL, uploading that file to an Upload URL as form data.

# Download email attachments to `/tmp`, upload to Amazon S3

This workflow (opens new window) is triggered by incoming emails. When copied, you’ll get a workflow-specific email address you can send any email to. This workflow takes any attachments included with inbound emails, saves them to /tmp, and uploads them to Amazon S3.

You should also be aware of the inbound payload limits associated with the email trigger.