fish-shell/doc_src/fish_key_reader.txt

\section fish_key_reader fish_key_reader - explore what characters keyboard keys send

\subsection fish_key_reader-synopsis Synopsis
\fish{synopsis}
fish_key_reader [-c | --continuous] [-d | --debug-level] [-D | --debug-stack-frames]
\endfish

\subsection fish_key_reader-description Description

`fish_key_reader` can be used to interrogate the characters received by `fish` and figure out key binds. If the sequence of characters matches a key name recognized by the `bind` command, `bind`'s representation will be shown. Also output are decimal, hexadecimal and symbolic values of the character and the delay in milliseconds since the previous character was received.

Before exiting, the tool will output an example bind command which matches the sequence captured.

The timing data may be useful to determine a preferred `fish_escape_delay_ms` setting or learning the amount of lag introduced by `ssh` or `tmux`.

- `-c` or `--continuous` begins a session where mutlitple key sequences can be inspected. By default the program exits after capturing a single key sequence. Press `^D` twice or type `exit` to exit. 

- `-d` or `--debug-level=DEBUG_LEVEL` enables debug output and specifies a verbosity level. Like `fish -d`. 

- `-D` or `--debug-stack-frames=DEBUG_LEVEL` specifies how many stack frames to display when debug messages are written. The default is zero.