David,

On 2 Jul 2014, at 13:41, David Matthews <[email protected]> wrote:

> On 02/07/2014 13:20, Rob Arthan wrote:
>> Have you looked at System V shared memory (shmget/shmat etc.)?  This
>> seems to be available on most flavours of UN*X these days. However,
>> it is a long while since I have used these interfaces and they may
>> just move the problem from the world of ls and rm to the world of
>> ipcs and ipcrm.
> 
> Thanks for suggesting this.  I was hoping someone might be able to suggest 
> something.  However, looking a bit more closely, I can see a problem.  shmget 
> uses a "key" which has to be derived from an existing file via ftok.  That 
> looks as though it would require a file to be created in the file system for 
> each process.  It could be zero size but I think it leads to the problem 
> you've identified.

I don’t think you have to use ftok (in fact, I have never used it). However you 
do need some scheme for allocating the numbers. I don’t know if you can arrange 
to have shared memory segments automatically disappear when all related 
processes die (which is why I thought you might just be moving the problem into 
a different namespace).

Regards,

Rob.
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