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Re: If $HISTFILE is set to /dev/null and you execute more commands than

From: Chet Ramey
Subject: Re: If $HISTFILE is set to /dev/null and you execute more commands than $HISTFILESIZE, /dev/null is deleted.
Date: Fri, 30 Jan 2015 14:25:35 -0500
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.10; rv:31.0) Gecko/20100101 Thunderbird/31.4.0

On 1/30/15 2:09 PM, Jonathan Hankins wrote:
> A test with the POSIX S_ISREG macro on HISTFILE will determine if it, or
> the file it points to in the case of a symlink, is a regular file.
> Just looked through the source, and it looks like general.c:file_exists()
> does not do any special handling of non-regular files, and
> lib/readline/histfile.c:history_do_write() calls open() and rename() on
> HISTFILE without checking if it is a non-regular file, which I imagine
> could lead to various "bad things" in the case of pipes, char and block
> devices, etc. such as what the OP pointed about about "/dev/null".

Well, like always, it depends.  The current implementation allows a user
to use a named pipe with a different program running to be a `history
file'.  That flexibility can be valuable.

I don't think that readline should be attempting to do backups of non-
regular files, though.  The history file truncation code, which is called
when HISTFILESIZE is changed, already rejects attempts to use non-regular

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU    address@hidden    http://cnswww.cns.cwru.edu/~chet/

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