Type Alias BuiltinFn 

pub type BuiltinFn = extern "C" fn(host: *const HostApi, argc: usize, argv: *const *const c_char) -> c_int;

A plugin-provided command handler.

• host — the host API table (call back into the shell through it).
• argc — number of elements in argv.
• argv — NUL-terminated C strings; argv[0] is the command name, argv[1..] the arguments. Valid only for the duration of the call; copy anything you need to keep.

Returns the command’s exit status (0 = success), like any shell builtin.