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Subject: Re: $RANDOM in function in pipe do not get reseeded
To: zsh-workers@zsh.org
References: <20170330112523.GA28110@t420s.epfl.ch>
From: Eric Cook <llua@gmx.com>
Message-ID: <ea289ab7-a75b-fc93-e682-884486c52c20@gmx.com>
Date: Thu, 30 Mar 2017 09:25:39 -0400
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On 03/30/2017 07:25 AM, tharvik@gmail.com wrote:
> Hello,
> 
> There is some strange behavior with $RANDOM, because you don't
> seed after forking.
> 
> For a testcase, here you go
> --
> Define a function echoing the value of $RANDOM
> ```
> get_random() {
>         echo "${RANDOM}"
> }
> ```
> Run it trough a pipe
> ```
> get_random | cat
> ```
> If you run it multiple times, the output is the same.
> --
> 
> There is the patch linked, which fixes it.
> 
> Have a nice day!
> 

from zshparam:
RANDOM <S>
       A pseudo-random integer from 0 to 32767, newly generated each time this parameter is referenced.  The  random  number
       generator can be seeded by assigning a numeric value to RANDOM.

       The  values  of  RANDOM form an intentionally-repeatable pseudo-random sequence; subshells that reference RANDOM will
       result in identical pseudo-random values unless the value of RANDOM is referenced or seeded in the  parent  shell  in
       between subshell invocations.