can't set HISTFILE to /dev/null

can't set HISTFILE to /dev/null

[Danek Duvall]

A colleague of mine saw this today:

    zsh: locking failed for /dev/null: operation not supported: reading anyway

Turns out he was setting HISTFILE=/dev/null, rather than unsetting it.
4.3.10 was silent in this case, but 4.3.12 now complains.  Is this
intentional?

I've not seen the ENOTSUP, but he was doing something with zones that might
have changed the situation a bit.  Still, if I do

    HISTFILE=/dev/null
    fc -R

then I see

    zsh: locking failed for /dev/null: permission denied: reading anyway

and it appears to be coming from the same place in the code.

Thanks,
Danek

Re: can't set HISTFILE to /dev/null

[Peter Stephenson]

On Thu, 23 Jun 2011 12:46:24 -0700
Danek Duvall <duvall@comfychair.org> wrote:
> A colleague of mine saw this today:
> 
>  zsh: locking failed for /dev/null: operation not supported: reading anyway
>...
>  zsh: locking failed for /dev/null: permission denied: reading anyway
> 
> Turns out he was setting HISTFILE=/dev/null, rather than unsetting it.
> 4.3.10 was silent in this case, but 4.3.12 now complains.  Is this
> intentional?

Error messages apart, which is down to OS behaviour (both of those look
reasonable), this is behaving as designed.  We've had problems with
history file locking in the past, which can cause silent corruption, so
it now alerts the user if there was a failure to lock the file so they
can do something about it.

Using /dev/null was never a supported method of turning *off* history
saving --- indeed, it doesn't turn it off, the shell busily saves all
the contents straight to the bit bucket, which is a waste of time.  This
has always happened, all that's changed is that the shell now says "this
doesn't seem to be doing what I expect, is this what you really wanted?"

The recommended way of turning off file saving (by me, anyway) is to set
SAVEHIST to 0.

-- 
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Re: can't set HISTFILE to /dev/null

[Vincent Lefevre]

On 2011-06-23 12:46:24 -0700, Danek Duvall wrote:
> A colleague of mine saw this today:
> 
>     zsh: locking failed for /dev/null: operation not supported: reading anyway
> 
> Turns out he was setting HISTFILE=/dev/null, rather than unsetting it.
> 4.3.10 was silent in this case, but 4.3.12 now complains.  Is this
> intentional?

Locking is intentional (4.3.10 did that incorrectly, and the history
file could become corrupt, in particular under NFS). If you really
want HISTFILE=/dev/null, you can try to unset HIST_FCNTL_LOCK.

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <http://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <http://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / Arénaire project (LIP, ENS-Lyon)

Re: can't set HISTFILE to /dev/null

[Bart Schaefer]

On Jun 24,  9:54am, Peter Stephenson wrote:
}
} Using /dev/null was never a supported method of turning *off* history
} saving

Seems to me it was more likely intended to turn off history *loading*.
SAVEHIST=0 won't do that, nor will HISTSIZE=0 (though it'll all get
thrown away after loading in the latter case).

However, the right way is to unset HISTFILE, not set it to /dev/null.