please use M-x clean-buffer-list instead, which is defined in midnight.el.

clean-buffers is a little tool that used to clean useless buffers which means buffers match specify regex (see clean-buffer-useless-buffer-names) or undisplayed time exceeded certain time (see clean-buffer-useless-buffer-timeout)

config useless-buffer-names or useless-buffer-time-out and then execute the following commands:

clean-buffers-kill-useless-buffers to clean useless buffers

or clean-buffers-turn-on-auto-clean-buffers to clean useless buffers automatically

• clean-buffers-kill-active-buffer - If no-nil, will clean active buffer. Default to nil.
• clean-buffers-kill-proces-holding-buffer - If non-nil, will clean process-holding buffer. Default to nil
• clean-buffers-judge-useless-buffer-functions - function list which used to determine a buffer is useless or not the function will take a buffer as the only argument and should return non-nil when the buffer is a useless buffer.
• clean-buffers-useless-buffer-time-out - buffers who's undisplayed time exceeded this value will be considered useless
• clean-buffers-useless-buffer-names - buffers who's name match one regex in this value will be considered useless.
• clean-buffers-useful-buffer-names - buffers who's name match one regex in this value will not considered useless.