# `FileName`

A file's name every common file system takes: no `/` or `\`, none of Windows' reserved characters or device names, at most 255 bytes: `report.pdf`.

[Software](types.md#software); not ordered; since Jadpo 0.1.0.

## Make one

Build one from its text, `FileName("report.pdf")`, which checks it: text that isn't one breaks `format`.

`text.parse(raw, as: FileName)` reads one from its text; text that isn't one at all fails `malformed`, such as `notes/today.txt`, `notes\today.txt` or `"a\u0000b"`.

## Text, JSON and storage

`text.from` writes its canonical text, the one form `text.parse` reads back. JSON sends its canonical text as a string.

| Text | JSON |
|---|---|
| `report.pdf` | `"report.pdf"` |
| `Résumé 2026.docx` | `"Résumé 2026.docx"` |
| `.gitignore` | `".gitignore"` |
| `archive.tar.gz` | `"archive.tar.gz"` |
| `CONSOLE.txt` | `"CONSOLE.txt"` |

It is stored in one column named for the field, of type `text`. `.gitignore` is stored as `'.gitignore'`.

## Shown to people

`text.format(value, locale:)` shows it to people in their locale.

With `locale: Locale.en_gb`:

| Value | Shown |
|---|---|
| `report.pdf` | `report.pdf` |
| `Résumé 2026.docx` | `Résumé 2026.docx` |
| `.gitignore` | `.gitignore` |
| `archive.tar.gz` | `archive.tar.gz` |
| `CONSOLE.txt` | `CONSOLE.txt` |

## Operations

It has the contract's own operations: `text.parse`, `text.from`, `text.format`, `json.read`, `json.write` and `==`. It isn't ordered, so `<` and sorting don't take it. [Every standard type meets one contract](../topics/every-standard-type-meets-one-contract.md) says how they work.