From: "Lawrence Velázquez" <larryv@zsh.org>
To: "Felipe Contreras" <felipe.contreras@gmail.com>
Cc: zsh-users@zsh.org
Subject: Re: Temporary variable compatibility
Date: Tue, 21 Mar 2023 21:03:14 -0400 [thread overview]
Message-ID: <94b397e5-bc81-40fa-b7bf-c7ab9a151744@app.fastmail.com> (raw)
In-Reply-To: <CAMP44s0qQ3yOD6a4cpg-RVOOrjKfHL6ZyaTry4xys9eQ9cD7tA@mail.gmail.com>
On Tue, Mar 21, 2023, at 8:21 PM, Felipe Contreras wrote:
> I found a discrepancy between different shells:
>
> f() { echo $var; }
> var=1 f
> test -z "${var-}"
>
> Both zsh, bash, and dash set the variable temporarily, but ksh does not.
>
> In zsh the emulation of ksh and sh both keep the variable assignment.
>
> Is this the POSIX standard?
POSIX.1-2017 leaves it unspecified, so both behaviors are conformant.
As per section 2.9.1 "Simple Commands" (e.g., something like "var=val
cmd"):
- If the command name is a function that is not a standard
utility implemented as a function, variable assignments
shall affect the current execution environment during the
execution of the function. It is unspecified:
- Whether or not the variable assignments persist
after the completion of the function
- Whether or not the variables gain the export
attribute during the execution of the function
- Whether or not export attributes gained as a
result of the variable assignments persist after
the completion of the function (if variable
assignments persist after the completion of the
function)
https://pubs.opengroup.org/onlinepubs/9699919799/utilities/V3_chap02.html#tag_18_09_01
> If so, then how should one temporarily set a variable? A subshell?
That's probably the most portable approach, yes.
--
vq
prev parent reply other threads:[~2023-03-22 1:06 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2023-03-22 0:21 Felipe Contreras
2023-03-22 1:03 ` Lawrence Velázquez [this message]
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