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From: "Lawrence Velázquez" <larryv@zsh.org>
To: Sheogorath <zsh@sheogorath.shivering-isles.com>
Cc: zsh-workers@zsh.org
Subject: Re: Bug report: Strange behaviour with random, sort and uniq
Date: Sat, 25 Feb 2023 18:21:56 -0500	[thread overview]
Message-ID: <97de94e6-ec50-4f38-962a-c066593bccbf@app.fastmail.com> (raw)
In-Reply-To: <010701868ad0a7e8-be8c1ddd-a63c-4002-926a-b7ba25a0cebb-000000@eu-central-1.amazonses.com>

On Sat, Feb 25, 2023, at 6:02 PM, Sheogorath wrote:
> I was running the following command in a terminal:
> for i in $(seq 0 100); do echo $((1 + RANDOM % 6)); done | sort | uniq
> -c
> When run twice after each other, it produces the same output:

This command uses RANDOM in a subshell.


	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.

> However, this changes, as soon as one run the command without the 'sort
> | uniq -c' piping:
> for i in $(seq 0 100); do echo $((1 + RANDOM % 6)); done

This command does not use RANDOM in a subshell.

> I also validated, that this behaviour doesn't exist in bash.

RANDOM works differently in bash.


      reply	other threads:[~2023-02-25 23:22 UTC|newest]

Thread overview: 2+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2023-02-25 23:02 Sheogorath
2023-02-25 23:21 ` Lawrence Velázquez [this message]

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