[olug] Odd results from /bin/sh (GNU bash) and the "test" command...

[Kevin]

A filesystem can also deny write access if it has reason to do so. I
bet the guys at my last job would love to know why ext3 sometimes
feels it necessary to switch to read-only mode. On production database
servers, this results on urgent calls at 8:01 am.

On Thu, Feb 25, 2010 at 18:56, Will Langford <unfies at gmail.com> wrote:
>>
>> But when the file is in /sys, the results are consistent:
>> $ mount | grep sysfs
>> none on /sys type sysfs (rw,noexec,nosuid,nodev)
>>
>> $ cat /sys/bus/pci/drivers_probe
>> cat: /sys/bus/pci/drivers_probe: Permission denied
>>
>> $ sudo -i
>> # cat /sys/bus/pci/drivers_probe
>> cat: /sys/bus/pci/drivers_probe: Permission denied
>>
>> I wonder if it is a sysfs problem...?
>>
>>
> sysfs... is... not your typical file system.  afaik, a fs can deny read
> access to something if you're intentionally not supposed to be able to read
> it -- ie: if there's nothing to read, deny the low level read ops from
> working, etc.
>
> I believe /sys/bus/pci/drivers_probe is a write only 'object' if you will ?
>
> -Will
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