On Wed, Aug 2, 2023, 10:45 Chet Ramey <chet.ra...@case.edu> wrote:
>
> On 7/27/23 10:16 PM, Grisha Levit wrote:
> > If the `history' builtin is used with no filename argument and the HISTFILE
> > variable is unset, the Readline default history file ~/.history is used.
>
> It makes sense to use some default filename if the user explicitly asks
> for the history to be read or written. Better than silently doing nothing
> or (slightly better) warning if HISTFILE is unset.
>
> > Since Bash normally doesn't perform any history file operations if HISTFILE
> > is empty or unset, I think it would make sense for `history' to do the same.
>
> What does `normally' mean here? I can see not reading from the history at
> startup or not writing to it at shell termination, but in your example the
> `history' builtin is being used to explicitly save the history somewhere.
The way I encountered this was that I usually run `HISTFILE=' when I
want to disable saving history for a particular session. At some
point I added `history -a' to PROMPT_COMMAND, but this combination
results in the (accurate) error message:
bash: history: : cannot create: No such file or directory
So I thought I would instead do `unset HISTFILE' -- this made the
error go away and I confirmed ~/.bash_history was not getting updated
(and neither was any other file!). At some later point I created
~/.history and then later noticed that this file started getting
written by `history -a'.
My mental model was "the history builtin with no filename argument
operates on whatever history file the shell is set up to write to on
shutdown" and "explicitly setting to null or unsetting HISTFILE tells
the shell not to save history anywhere".
Now I have `[[ ! ${HISTFILE-} ]] || history -a' instead -- so problem solved.
I would guess that the majority of `history -[anrw]' invocations are
`history -a' in PROMPT_COMMAND and the like, and that users unset
HISTFILE to signal that they don't want history written -- and usually
this works fine because they don't have a ~/.history to append to.
So while using ~/.bash_history when neither HISTFILE nor an argument
is supplied would be reasonable behavior, I think changing it now
would be surprising for anyone who (a) uses `history -a' in
PROMPT_COMMAND (b) uses `unset HISTFILE' to disable history file
writing and (c) does not have a `.history' file in their home
directory -- which I think describes a lot of users based on [1] [2].
Sorry for the long message.
[1] https://mywiki.wooledge.org/BashFAQ/077
[2] https://mywiki.wooledge.org/BashFAQ/088
