[erlang-questions] Erlang Shell History discussion (Was: Re: OTP R16A has been released)

[Fred Hebert]

On 01/31, Pierre Fenoll wrote:
> Hi Fred!  and sorry to diverge this thread…
> Why do you want a history file per erlshell? bash only uses one:
> ~/.bash_history
> You only need one ~/.erlang.history, don't you?
> 

Because from one computer you can be using remote shells to many
different Erlang VMs running with different names.

I always figured that the history for test@REDACTED would be something
you would like a different history from something like prod@REDACTED,
especially considering histories disappearing over time and whatnot.
That way, different projects or nodes get isolated histories. 

So far I've enjoyed it and the fact I can get a clean shell history for
projects I haven't touched in months whereas the shell I use to test
everything locally (nonode@REDACTED) is chuck full of unrelated garbage
and experiments.

If people tell me they don't give a crap, I'm open to consider getting
rid of that, but there's really no complexity attached to any of this. I
simply add a call atom_to_list(node()) when opening the table/file and
that's it.

Regards,
Fred.

> On 31 January 2013 00:07, Fred Hebert <mononcqc@REDACTED> wrote:
> 
> > That's what it is. It searches the line stack. It's a *history-search*
> > patch, not a general history-saving patch.
> >
> > I have https://github.com/ferd/erlang-history that implements a search
> > that can be saved, but there's still work to do in it before it can be
> > good enough for OTP:
> >
> > 1. it relies on DETS, and DETS seems to corrupt files from time to time
> >    either when too many shells write to it, or when it's interrupted
> >    while dumping. I want to get rid of DETS at some point for some other
> >    line utility, maybe disk_log.
> > 2. I'll need to make it use a .erlang/ directory in $HOME rather than
> >    plenty of .erlang.$NAME files. There's a truckload of .erlang.*
> >    config files around, and one per named shell is problematic.
> > 3. Multiple shells are implemented in an okay way, but there may be a
> >    need to correct codes when many shells write to the same file
> >    (usually multiple non-distributed shells).
> > 4. The usual OTP cleanup and formatting is required.
> > 5. I haven't considered the issue of multiple encodings used in the same
> >    shell history file yet.
> > 6. I haven't asked the OTP team what they think should be done at that
> >    point, but I'd be fine forking this thread to start discussing it.
> >
> > Lately I haven't had the time/motivation to do that heavy lifting,
> > but with the book and university done, I'll probably find time here and
> > there to try and make a better implementation.
> >
> > In the mean time, I'll keep the repository above up to date. It's not
> > yet ready for R16A support -- I use the compiler versions to deal with
> > things and the new code can't be the same to make it there. It should
> > work fine with the new ^R support feature.
> >
> > Shell history is a tiny bit about injecting history in a shell and is
> > *mostly* about handling files on disk. Shell history search is pretty
> > much handling the line stack in the shell and edlin, so that one was
> > much simpler to deal with than history to make it part of OTP :)
> >
> > Regards,
> > Fred.
> >
> > On 01/30, Motiejus Jakštys wrote:
> > > On Wed, Jan 30, 2013 at 3:40 PM, Fred Hebert <mononcqc@REDACTED> wrote:
> > > > Also:
> > > >
> > > >   OTP-10739  Add search to Erlang shell's history. Thanks to Fred
> > > >    Herbert.
> > >
> > > History between sessions is not implemented (I get readline-style
> > > ctrl-r in same session fine which is super cool)?
> > >
> > > /home/motiejus$ erl -config hist.config -name labas
> > > Erlang R16A (erts-5.10) [source] [smp:2:2] [async-threads:10] [hipe]
> > > [kernel-poll:false]
> > >
> > > Eshell V5.10  (abort with ^G)
> > > (labas@REDACTED)1> application:get_all_env(kernel).
> > > [{hist_file,"erlang-history"},
> > >  {included_applications,[]},
> > >  {error_logger,tty},
> > >  {hist_size,120},
> > >  {hist_drop,["q().","init:stop()."]}]
> > > (labas@REDACTED)2> q().
> > > ok
> > > (labas@REDACTED)3> %
> > > /home/motiejus$ ls -lA | grep erlang
> > > -r--------  1 motiejus motiejus      20 Rgp 23 23:00 .erlang.cookie
> > >
> > >
> > > --
> > > Motiejus Jakštys
> > _______________________________________________
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> >