bug: can't write history file

bug: can't write history file

[Dmitry Karasik]

Hello,

After upgrading to 4.3.2, I've found that one of the features I love in zsh is
broken, namely the possibility to use the history file for both root and
non-root sessions.  Now, after I logout from "sudo zsh", I get this:

   zsh: can't write history file /home/dk/.zsh-history

I found that it is savehistfile() to blame, because it apparently is called
with writeflags=0, which bypasses all append/rewrite logic, falling back to
saving the file by renaming it to .zsh-history.new, and (correctly) refusing to
overwrite .zsh-history because the euid is different. If I'm correct in
this, the patch below fixes the problem:

--- hist.c.orig Tue Oct 24 15:45:28 2006
+++ hist.c      Tue Oct 24 15:45:47 2006
@@ -2163,7 +2163,7 @@
            readhistfile(fn, err, 0);
            hist_ignore_all_dups = isset(HISTIGNOREALLDUPS);
            if (histlinect)
-               savehistfile(fn, err, 0);
+               savehistfile(fn, err, writeflags & HFILE_APPEND);
 
            pophiststack();
            histactive = remember_histactive;


-- 
Sincerely,
	Dmitry Karasik

Re: bug: can't write history file

[Wayne Davison]

On Tue, Oct 24, 2006 at 04:17:40PM +0200, Dmitry Karasik wrote:
> I found that it is savehistfile() to blame, because it apparently is
> called with writeflags=0, which bypasses all append/rewrite logic

This is as it should be, because that code is re-writing the history
file to trim it.  As long as you use HIST_APPEND or SHARE_HISTORY, the
history from a root session should be added to the file -- just the
rewrite at the end will be skipped.

..wayne..

Re: bug: can't write history file

[Peter Stephenson]

Dmitry Karasik wrote:
> Hello,
> 
> After upgrading to 4.3.2, I've found that one of the features I love in zsh i
> s
> broken, namely the possibility to use the history file for both root and
> non-root sessions.  Now, after I logout from "sudo zsh", I get this:
> 
>    zsh: can't write history file /home/dk/.zsh-history
> 
> I found that it is savehistfile() to blame, because it apparently is called
> with writeflags=0, which bypasses all append/rewrite logic, falling back to
> saving the file by renaming it to .zsh-history.new, and (correctly) refusing 
> to
> overwrite .zsh-history because the euid is different. If I'm correct in
> this, the patch below fixes the problem:
> 
>...
> -               savehistfile(fn, err, 0);
> +               savehistfile(fn, err, writeflags & HFILE_APPEND);
>...

That line is the same in 4.2, so I presume what has changed is the
default options (how it reaches this code).  In that case it's
plausible that this should always have had that flag.  It would
be best if Wayne could comment about what he thinks did change,
but I'm not sure if he's around at the moment.

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR PLC, Churchill House, Cambridge Business Park, Cowley Road
Cambridge, CB4 0WZ, UK                          Tel: +44 (0)1223 692070


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Re: bug: can't write history file

[Dmitry Karasik]

On Tue, Oct 24, 2006 at 08:27:18AM -0700, Wayne Davison wrote:
> On Tue, Oct 24, 2006 at 04:17:40PM +0200, Dmitry Karasik wrote:
> > I found that it is savehistfile() to blame, because it apparently is
> > called with writeflags=0, which bypasses all append/rewrite logic
> 
> This is as it should be, because that code is re-writing the history
> file to trim it.  As long as you use HIST_APPEND or SHARE_HISTORY, the
> history from a root session should be added to the file -- just the
> rewrite at the end will be skipped.

That is possibly true, however before changing the code I did play with
HIST_APPEND and SHARE_HISTORY and I cannot confirm that setting these option
will work.  To support this, as far as I can see in the code,
"isset(APPENDHISTORY)" or "isset(SHAREHISTORY)" are only checked when
"writeflags & HFILE_USE_OPTIONS", which is actually never true in the second
call. 

> That line is the same in 4.2, so I presume what has changed is the
> default options (how it reaches this code).  In that case it's
> plausible that this should always have had that flag. 

I'm not sure what caused this problem not to appear in the previous versions,
but if you insist that this is the configuration problem, I'd like to ask you
to send me a minimalistic .zshenv that will not trigger the error and will save
the history correctly both under root and non-root. 

-- 
Sincerely,
	Dmitry Karasik

Re: bug: can't write history file

[Wayne Davison]

On Tue, Oct 24, 2006 at 06:15:06PM +0200, Dmitry Karasik wrote:
> as far as I can see in the code, "isset(APPENDHISTORY)" or
> "isset(SHAREHISTORY)" are only checked when "writeflags &
> HFILE_USE_OPTIONS", which is actually never true in the second call. 

Right.  As I said, this is as it should be.  That part of the code is
rewriting the file on exit, so it should never honor the incremental
options at that point -- it must always rewrite the file from scratch.

> I'd like to ask you to send me a minimalistic .zshenv that will not
> trigger the error and will save the history correctly both under root
> and non-root. 

One new option that I just remembered is HIST_SAVE_BY_COPY:  if you
unset that, the error will go away.  It is a little less safe of an
update, but it does allow root to update the user's file without
changing its ownership.  The alternative is to just live with the
occasional history-file warning while using a history-appending option
(I tested that that will still leave root's commands in the file).

..wayne..

Re: bug: can't write history file

[Dmitry Karasik]

> One new option that I just remembered is HIST_SAVE_BY_COPY:  if you
> unset that, the error will go away.  It is a little less safe of an
> update, but it does allow root to update the user's file without
> changing its ownership.  The alternative is to just live with the

Thanks! But it seems that I'm trying to reproduce it the wrong way...
I say "unset HIST_SAVE_BY_COPY" in .zshenv ... and nothing happens -
the warning is still there. What is the correct incantation?

-- 
Sincerely,
	Dmitry Karasik

Re: bug: can't write history file

[Wayne Davison]

On Tue, Oct 24, 2006 at 10:51:43PM +0200, Dmitry Karasik wrote:
> I say "unset HIST_SAVE_BY_COPY" in .zshenv ... and nothing happens -

You want unsetopt instead of unset.

..wayne..