file_header

The first N lines must match a regex (line-oriented). For a byte-level prefix check, prefer file_starts_with.

Fix: file_prepend — inject declared content at the top (preserves UTF-8 BOM).

Options

Option	Type	Required	Default	Description
lines	integer (>= 1)		20	Number of leading lines to consider.
pattern	string	yes		Rust regex. The first lines lines of each file in scope must match.

Plus the common paths, level, id, and when fields. This table is generated from the JSON Schema; option types and defaults are authoritative.

Example

A source file missing its copyright header

The rule fires on this repository:

src/
src/a.rs
src/b.rs

src/a.rs

fn a() {}

src/b.rs

// Copyright 2026
// SPDX-License-Identifier: Apache-2.0
fn b() {}

With this .alint.yml:

version: 1
rules:
  - id: copyright-header
    kind: file_header
    paths: "src/**/*.rs"
    pattern: "(?s)Copyright"
    lines: 3
    level: error

alint check reports:

--- src/a.rs -------------------------------------------------------------------
  x  error    copyright-header
              1:1  first 3 line(s) do not match required header /(?s)Copyright/

Summary (1 violation):
  x 1 error
  0 passing * 1 failing

Every source file carries the header

This repository is compliant:

src/
src/a.rs
src/b.rs

src/a.rs

// Copyright 2026
fn a() {}

src/b.rs

// Copyright 2026
// SPDX-License-Identifier: Apache-2.0
fn b() {}

With this .alint.yml:

version: 1
rules:
  - id: copyright-header
    kind: file_header
    paths: "src/**/*.rs"
    pattern: "(?s)Copyright"
    lines: 3
    level: error

alint check reports:

v All 1 rule(s) passed.