---
url: /process-functions/datasource-filesize.md
description: Retrieves the size of a specified file from the MODLR filesystem.
---

# datasource.fileSize

Retrieves the size of a specified file from the MODLR filesystem.

```js
datasource.fileSize(file_name)
```

#### Parameters

* `file_name` (string): The name of the file for which you want to retrieve the size.

#### Returns

* `number`: An integer representing the size of the file in bytes. Returns `0` if the file is invalid, does not exist, or an error occurs.

#### Examples

```js
var fileSizeInBytes = datasource.fileSize("my_file.txt");
if (fileSizeInBytes > 0) {
    console.log("File size:", fileSizeInBytes, "bytes");
} else {
    console.log("Error retrieving file size or invalid file.");
}
```