Re: Question on /proc API & bug in sysctl
Aaron Ucko (UCKO@vax1.rockhurst.edu)
Sat, 23 Mar 1996 15:23:14 -0600 (CST)
>> While looking at the code of the sysctl in /proc I found several
>> problems. The interface provided is buggy. By this I mean that it
>> does not respect the interface for file access. There should be
>> no difference between accessing a normal file in an ext2 filesystem
>> (for instance) and a file in /proc.
>>
>> To show the bug, just try to do a simple dd in /proc/sys/kernel/ostype
>> (for instance):
>> dd if=/proc/sys/kernel/ostype of=/dev/tty bs=1 skip=3
>>
>> You will see that whatever skip you provide you will always get
>> the string from the beginning. THIS IS NOT CORRECT AND DOES NOT
>> RESPECT THE INTERFACE.
>>
>> I know this a kind of details but you may come to a problem when
>> new BIG entries will be added to this directory aalong with
>> companion program to display contents.
>
>The reason for this behaviour is that most /proc entries do NOT support
>lseek().
Therefore the bug is in dd and not in the kernel: if dd finds that lseek
fails with such-and-such an error, it should just read the specified amount
of data itself and ignore it.
-- Aaron Ucko (ucko@vax1.rockhurst.edu; finger for PGP public key) | httyp!
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