Re: problems with RANDOM in subshells

[Peter Stephenson <pws@csr.com>]

Zefram wrote:
> Clint Adams wrote:
> >Should the random-seeding behavior be changed for subshells?
> 
> No.  We define $RANDOM to be a PRNG; zshparam(1) speaks of seeding it
> (by writing to $RANDOM).  Opening a subshell should not interfere with
> the PRNG sequence, which one might be relying on to be reproducible.

bash has the zsh behaviour, but ksh 88 handles subshells specially.
POSIX/SUS doesn't defined RANDOM, but we probably ought to get this
specified for David Korn's enhanced shell proposal, given that all three
shells under discussion already have RANDOM.

It does seem to me that it's unnecessarily hard for a user to take avoiding
action in a subshell.  At least providing the PID of the subshell process
as separate parameter might give them the start, e.g. make $ZSH_REALPID map
directly to getpid() --- obviously not with a very high degree of
randomness, but I don't think that was a problem in this case.  (The
advantage over providing a real `random' number is that it takes a minute
to write instead of a day.)

-- 
Peter Stephenson <pws@csr.com>                  Software Engineer
CSR Ltd., Science Park, Milton Road,
Cambridge, CB4 0WH, UK                          Tel: +44 (0)1223 392070


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