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Fixed-Width File

Fixed Width File
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Overview

The Fixed-Width File node for n8n enables you to read data from or write data to files formatted with fixed-width fields. In the "Read From File" operation, it parses a binary file (such as .txt or .dat) where each field has a specific width, extracting structured data from each line according to your field definitions.

Common scenarios:

  • Importing legacy data from mainframe or COBOL systems that use fixed-width text files.
  • Processing bank statements, payrolls, or other standardized reports delivered in fixed-width format.
  • Integrating with partners who provide or require data in fixed-width files.

Practical example:
You receive a batch of customer records in a fixed-width file, where each line contains a name (20 characters), age (3 characters), and balance (10 characters). This node can parse each line into a JSON object for further processing in your workflow.

Properties

Name Type Meaning
Binary Property String Name of the binary property from which to read the fixed-width formatted file's binary data.
Fields Fixed Collection Defines the structure of each record. Each field specifies:
- Property Name: Where to store the value (supports dot notation).
- Type: Data type (Boolean, Float, Integer, Number, String).
- Width: Number of characters for this field.
(Align is not used in "Read From File")
Options → End-of-Line Character String The character(s) that separate rows/records in the file (default: \n).
Options → Trim Options How to trim whitespace/padding from parsed values. Choices: Both, None, Left, Right. Default: Both.
Options → Relaxed Parsing Boolean If true, partial/incomplete lines are parsed without error. Default: false.

Output

Each output item represents a parsed record from the file:

{
  "json": {
    // Parsed fields as defined in "Fields"
    "property1": "value1",
    "property2": 123,
    ...
  },
  "pairedItem": <index>
}
  • The json object contains key-value pairs as specified by your "Fields" configuration.
  • If an error occurs and "Continue On Fail" is enabled, the output may include an error field describing the issue.

Binary output:
This operation does not produce binary output; it only reads/parses binary input.

Dependencies

  • External library: @evologi/fixed-width for parsing fixed-width files.
  • No external API keys or services required.
  • No special n8n environment variables needed.

Troubleshooting

Common issues:

  • Incorrect field widths: If the sum of field widths does not match the actual line length, parsing errors or misaligned data may occur.
  • Missing binary data: If the specified binary property does not exist on the input item, that item will be skipped.
  • Partial lines: By default, incomplete lines cause errors unless "Relaxed Parsing" is enabled.
  • Encoding mismatches: If the file uses an unexpected encoding, parsing may fail or produce garbled results.

Error messages:

  • "Cannot read properties of undefined (reading 'binary')": The input item lacks the expected binary property. Check your input and the "Binary Property" setting.
  • "Invalid field definition": Your "Fields" configuration may be missing required attributes like width or property name.
  • "Line too short" or similar: The file contains lines shorter than the total field width. Enable "Relaxed Parsing" if this is acceptable.

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