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Re: [Bug-readline] [PATCH] readline/histfile.c: Check and retry write() operation in history_truncate_file()
- From: Chet Ramey <chet dot ramey at case dot edu>
- To: Chen Gang <gang dot chen dot 5i5j at gmail dot com>, Andreas Schwab <schwab at linux-m68k dot org>
- Cc: chet dot ramey at case dot edu, palves at redhat dot com, gdb-patches at sourceware dot org, binutils at sourceware dot org, bug-readline at gnu dot org, amodra at gmail dot com
- Date: Fri, 20 Jun 2014 17:53:38 -0400
- Subject: Re: [Bug-readline] [PATCH] readline/histfile.c: Check and retry write() operation in history_truncate_file()
- Authentication-results: sourceware.org; auth=none
- References: <5397C077 dot 1080702 at gmail dot com> <53A1F78A dot 8020508 at case dot edu> <53A23D77 dot 1040905 at gmail dot com> <53A3F78E dot 6020803 at gmail dot com>
- Reply-to: chet dot ramey at case dot edu
On 6/20/14, 4:57 AM, Chen Gang wrote:
> On 06/19/2014 09:31 AM, Chen Gang wrote:
>> On 06/19/2014 04:33 AM, Chet Ramey wrote:
>>> On 6/10/14, 10:35 PM, Chen Gang wrote:
>>>> For regular file, write() operation may also fail, so check it too. If
>>>> write() return 0, can simply wait and try again, it should not suspend
>>>> infinitely if environments have no critical issues.
>>> Readline-6.3 checks the return value from write() and returns a non-zero
>>> value to the history_truncate_file caller. I really don't think that
>>> waiting forever if write continues to return 0 is a great idea; an error
>>> return is enough to let the caller deal with it.
> Oh, sorry, after think of again, for me, we have to waiting forever if
> write() continues to return 0.
There aren't really any plausible conditions under which write(2) returns
0 instead of -1 when writing a non-zero number of bytes to a regular file.
> When this case happens, the file is already truncated, and the left data
> which is writing to file will be free after return from
> If return an error code in this case, the caller can not deal with it --
> the log data which should be remained, have been lost, can not get them
> back again.
However, you're right about the data being lost if write fails and returns
-1. Since the sequence of operations is open-read-close-open-write-close, I
think I will change the code for the next version to use a scheme similar
to history_do_write() and restore the original version of the file if the
``The lyf so short, the craft so long to lerne.'' - Chaucer
``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, ITS, CWRU firstname.lastname@example.org http://cnswww.cns.cwru.edu/~chet/