# Description
Add a `command_not_found` function to `$env.config.hooks`. If this
function outputs a string, then it's included in the `help`.
An example hook on *Arch Linux*, to find packages that contain the
binary, looks like:
```nushell
let-env config = {
# ...
hooks: {
command_not_found: {
|cmd_name| (
try {
let pkgs = (pkgfile --binaries --verbose $cmd_name)
(
$"(ansi $env.config.color_config.shape_external)($cmd_name)(ansi reset) " +
$"may be found in the following packages:\n($pkgs)"
)
} catch {
null
}
)
}
# ...
```
# User-Facing Changes
- Add a `command_not_found` function to `$env.config.hooks`.
# Tests + Formatting
Don't forget to add tests that cover your changes.
Make sure you've run and fixed any issues with these commands:
- `cargo fmt --all -- --check` to check standard code formatting (`cargo
fmt --all` applies these changes)
- `cargo clippy --workspace -- -D warnings -D clippy::unwrap_used -A
clippy::needless_collect` to check that you're using the standard code
style
- `cargo test --workspace` to check that all tests pass
# After Submitting
If your PR had any user-facing changes, update [the
documentation](https://github.com/nushell/nushell.github.io) after the
PR is merged, if necessary. This will help us keep the docs up to date.
