``fish_key_reader`` is used to explain how you would bind a certain key sequence. By default, it prints the :ref:`bind <cmd-bind>` command for one key sequence read interactively over standard input.
If the character sequence matches a special key name (see ``bind --key-names``), both ``bind CHARS ...`` and ``bind -k KEYNAME ...`` usage will be shown. In verbose mode (enabled by passing ``--verbose``), additional details about the characters received, such as the delay between chars, are written to stderr.
-``-c`` or ``--continuous`` begins a session where multiple key sequences can be inspected. By default the program exits after capturing a single key sequence.
In verbose mode, the delay in milliseconds since the previous character was received is included in the diagnostic information written to stderr. This information may be useful to determine the optimal ``fish_escape_delay_ms`` setting or learn the amount of lag introduced by tools like ``ssh``, ``mosh`` or ``tmux``.