Re: EINVAL when reading files in /proc/sys

From: kuznet@ms2.inr.ac.ru
Date: Sat Jan 22 2000 - 12:32:13 EST


Hello!

> zeus 62 % ls -l /proc/sys/net/ipv4/route/flush
> -rw-r--r-- 1 root root 0 Jan 20 16:42

Seems, it is one of those magic bugs, which are fixed, but return back. 8)
I remember Andi repaired this once!

> This is really the only thing that severely breaks walking /proc/sys
> with a simple shell script.

One warning. If you plan to write the information read from sys/net
back to sys/net, be ready to surprises.

Particularly, setting "forward" (and "flush", and, probably, a few
of another entries) has side effects and saving them is undefined.

Moreover, essentially, the script, which scans all sys/ and would-be "saves"
its content is non-sense. It should touch only variables, which are safe
to touch and, hence, should not touch variables with sense not clear
to script's author (or even undocumented variables, which will be _always_
present and are supposed to be touched only by expert's request/advice
in well understood curcumstances.)

It is the reason why I am not bothered too much by attributes on "flush".

Alexey

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