:title
cli_arg

:sig
String cli_arg(Request& context, String key, String default_value = "")

:see
>1_CLI
>cli_input

:content
Reads one value from the merged `cli_input(context)` parameter tree.

If the key is missing, or the resolved value is empty, `default_value` is returned.

```cpp
CLI(Request& context)
{
    String action = cli_arg(context, "action", "help");
    print("action=", action, "\n");
}
```

For commands that need multiple values or typed reads, prefer calling `cli_input(context)` once and reading the returned `DValue` directly.