command

Shell out to an external CLI per matched file. Exit 0 is a pass; non-zero is one violation whose message is the (truncated) stdout+stderr. Working directory is the repo root; stdin is closed.

Argv tokens accept the same path-template substitutions as pair and for_each_dir: {path}, {dir}, {stem}, {ext}, {basename}, {parent_name}. The first token is the program (looked up via PATH if it's a bare name).

Environment threaded into the child:

Var	Value
ALINT_PATH	matched path (relative to root)
ALINT_ROOT	absolute repo root
ALINT_RULE_ID	the rule's id:
ALINT_LEVEL	error / warning / info
ALINT_VAR_<NAME>	one per top-level vars: entry
ALINT_FACT_<NAME>	one per resolved fact, stringified

timeout: <seconds> (default 30) bounds each invocation; past the limit the child is killed and a violation reports the timeout.

Output is drained while the child runs (a child writing more than a pipe buffer cannot deadlock), and after the child exits alint waits at most 2 seconds for descendants still holding its output pipes. What the timeout kills depends on whether alint's stdin is a terminal. In a non-interactive run (CI, the language server, piped stdin) each spawned process (the command rule, generated_file_fresh, command_idempotent, the command fix, custom: facts) gets its own process group on Unix: the timeout kills the whole group, grandchildren included, and descendants left holding the output pipes after a normal exit are killed too. In an interactive run (stdin is a terminal) the child stays in alint's process group so Ctrl-C reaches it and it can prompt on /dev/tty; the timeout then kills only the direct child. A timeout too large to represent means no deadline. On Windows only the direct child is killed.

Trust gate. Every process-spawning rule kind — command, generated_file_fresh, and command_idempotent — is allowed only in the user's own top-level config. Any of them introduced via extends: (local file, HTTPS URL, or alint://bundled/) is a load-time error — the same gate that protects custom: facts. Adopting a published ruleset must never imply granting it arbitrary code execution.

Path confinement + allow_out_of_root. Every config-declared path is confined to the repo root — a rule can't read or resolve a file outside the tree it was pointed at. The top-level-only allow_out_of_root: key relaxes this for reads (json_schema_passes schema_path:, pair_hash target:, registry_paths_resolve source:) when a trusted config must reference an external file. It is rejected from extends:'d rulesets (same trust model as the spawn gate above) and a permitted read emits a note. See Configuration → allow_out_of_root.

--changed interaction: command is a per-file rule, so under alint check --changed it spawns only for files in the diff. The expensive check is automatically incremental in CI.

---

Options

Option	Type	Required	Default	Description
command	list of string	yes		Argv tokens. The first token is the program (looked up via PATH if it's a bare name); remaining tokens accept {path} and friends.
timeout	integer (>= 1)		null	Per-file timeout in seconds. Default 30. Past this, the child is killed and a violation reports the timeout.

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

Example

A file the wrapped checker flags

The rule fires on this repository:

• src/
• src/a.rs✗

  ✗ error no-todo-markers

  `sh` failed (exit 1): 1:// TODO: drop the debug hook before release

• src/b.rs✓

src/a.rs

// TODO: drop the debug hook before release
fn a() {}

src/b.rs

fn b() {}

With this .alint.yml:

version: 1
rules:
  - id: no-todo-markers
    kind: command
    paths: "src/**/*.rs"
    command: ["sh", "-c", "if grep -n TODO \"{path}\"; then exit 1; fi"]
    level: error

alint check reports:

--- src/a.rs -------------------------------------------------------------------
  x  error    no-todo-markers
              `sh` failed (exit 1):
              1:// TODO: drop the debug hook before release

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

Files the wrapped checker passes

This repository is compliant:

• src/
• src/lib.rs✓
• src/main.rs✓

src/lib.rs

pub fn ok() {}

src/main.rs

fn main() {}

With this .alint.yml:

version: 1
rules:
  - id: no-todo-markers
    kind: command
    paths: "src/**/*.rs"
    command: ["sh", "-c", "if grep -n TODO \"{path}\"; then exit 1; fi"]
    level: error

alint check reports:

v All 1 rule(s) passed.