From: Peter Stephenson <p.w.stephenson@ntlworld.com>
To: zsh-users@zsh.org
Subject: Re: random once but not twice
Date: Sun, 12 Nov 2017 19:08:06 +0000 [thread overview]
Message-ID: <20171112190806.7f2cf68a@ntlworld.com> (raw)
In-Reply-To: <86375k5t8w.fsf@zoho.com>
On Sat, 11 Nov 2017 23:46:07 +0100
Emanuel Berg <moasen@zoho.com> wrote:
> Emanuel Berg wrote:
>
> > echo $(echo $RANDOM) # always the same
>
> OK, I learned on #zsh@freenode that $RANDOM
> doesn't do anything but is inherited from the
> parent shell where there has been no access and
> thus no new value.
>
> : $RANDOM; vid=$(random-video $vid_dir)
You can also work around with the following rand48 function.
(rand48; print $REPLY)
(rand48; print $REPLY)
pws
# Genrate a 48-bit pseudo-random number as a floating point value between
# 0 and 1 in $REPLY.
#
# This version is slow but works aroud the fact that the random number
# seed doesn't propagate back from a subshell by storing the seed in
# a file.
#
# You can speicify a file name, else ${ZDOTDIR:-~}/.zsh-rand48-seeed is used,
# but if using the default be careful about simultaneous accesses from
# multipe shells.
zmodload zsh/mathfunc
local file=${1:-${ZDOTDIR:-~}/.zsh-rand48-seed}
local seed
if [[ -f $file ]]; then
seed=$(<$file)
fi
typeset -g REPLY=$(( rand48(seed) ))
print $seed >$file
next prev parent reply other threads:[~2017-11-12 19:08 UTC|newest]
Thread overview: 12+ messages / expand[flat|nested] mbox.gz Atom feed top
2017-11-11 18:57 Emanuel Berg
2017-11-11 21:52 ` Mikael Magnusson
2017-11-11 22:26 ` Emanuel Berg
2017-11-11 22:32 ` Emanuel Berg
2017-11-11 22:46 ` Emanuel Berg
2017-11-12 19:08 ` Peter Stephenson [this message]
2017-11-12 20:02 ` Emanuel Berg
2017-11-12 20:15 ` Bart Schaefer
2017-11-12 20:18 ` Emanuel Berg
2017-11-13 0:15 ` Emanuel Berg
2017-11-13 4:56 ` Bart Schaefer
2017-11-13 5:07 ` Emanuel Berg
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