Input · Files

Fixed-width Reader

Reads a text file whose columns sit at fixed character positions, such as a mainframe export or a legacy feed, slicing each line at the positions you set on a ruler over the file's first lines. Header row, start line, encoding and row limit work as in the CSV Reader.

Also known as: Fixed length, flat file, .dat, .prn, Alteryx .flat

How it works

Give the node a file in Source, as for the CSV Reader. The Columns section shows a ruler over the file's first lines: click a position to start a column there, or type the widths (3, 5, 4) and the columns are laid out from the first character. Each column has a name, a start, a width or end position and an optional type. Every line is cut at those positions; the pieces are trimmed and typed the way a CSV read types them, so a short line leaves its missing columns blank (NULL), and 0042 stays text unless you type the column as a number. With Header row on, the first line names the columns; off, they are column1, column2, and so on. Encoding and Row limit are the CSV Reader's own controls. A .dat or .prn file dropped on the canvas becomes a CSV Reader first; when its lines all share one length, that reader's panel offers Switch to Fixed-width Reader, which keeps the node's wires and file.

Inputs and outputs

Settings

Nothing to set in the Attributes panel: see How it works for where this node is set up.

Example

A bank statement feed with no delimiters, three columns wide:

The line 00012345 2026-03-14       -42.50 becomes account 00012345 (text, leading zeros kept), posted 2026-03-14 and amount −42.5.

More in Files

• CSV Reader — Reads a CSV or other delimited text file, such as a TSV. Column types are detected for you, and you can override them or read every column as text.
• JSON Reader — Reads a .json, .jsonl or .ndjson file as a table. A JSON array of objects and one-object-per-line files are both detected automatically.
• Parquet Reader — Reads a Parquet file and keeps the column types stored in it.
• Excel Reader — Reads one worksheet of an Excel workbook, the first sheet unless you pick another.
• Geo Reader — Reads a map file with its geometry: GeoJSON, Shapefile (also zipped), GeoPackage, GML, KML/KMZ, GPX, FlatGeobuf or MapInfo TAB. For a file with several layers, you pick which layer to read.
• XML Reader — Reads an XML file into a table. It finds the repeating record element for you, so each record becomes a row.
• SQLite Reader — Reads one table from a local SQLite database file (.sqlite, .sqlite3 or .db). You pick the table from the file's list of tables.
• Locra Table Reader — Reads a .ddtable file saved by Write Locra Table, in this project or another one. The column formats come back too, so everything prints as it did.