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From: Stephane Chazelas <stephane@chazelas.org>
To: Bart Schaefer <schaefer@brasslantern.com>
Cc: Peter Stephenson <p.w.stephenson@ntlworld.com>,
	Zsh hackers list <zsh-workers@zsh.org>
Subject: Re: [PATCH (not final)] (take three?) unset "array[$anything]"
Date: Mon, 14 Jun 2021 08:19:40 +0100	[thread overview]
Message-ID: <20210614071940.xugzcv63habfegjo@chazelas.org> (raw)
In-Reply-To: <CAH+w=7YKqdJJvLjF3-oEiwc2pQqosUZLcJz0OC7-KqCA7_e11Q@mail.gmail.com>

2021-06-13 14:44:03 -0700, Bart Schaefer:
> On Sun, Jun 13, 2021 at 12:50 PM Peter Stephenson
> <p.w.stephenson@ntlworld.com> wrote:
> >
> > Yes, in fact those are the same thoughts that flitted through my mind.
> 
> One other idea ... NO_UNSET could warn if you unset something that's
> not set, as well as when you $deref something that's not set.  That
> would at least blat at you if your hash key was misinterpreted.

Note that nounset is a POSIX option. And for the unset special
utility:

"Unsetting a variable or function that was not previously set
shall not be considered an error and does not cause the shell to
abort."

POSIX has no jurisdiction over arrays/hashes, but that does mean
we can't have unset fail on unset variables when in sh emulation
at least.

A shell that would fail upon:

  unset var

When var was not previously set would not be compliant.

A script that would do

  unset "var[foo]"

Would not be a POSIX script as var[foo] is not a valid variable
name, so implementations are free to do whatever they want for
them. But if zsh returned failure for when var[foo] is not set
and not in unset var, that would make it quite inconsistent.

Changing the behaviour would likely break some scripts that use
errexit as well.

-- 
Stephane


  reply	other threads:[~2021-06-14  7:20 UTC|newest]

Thread overview: 58+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2019-12-16 21:10 regexp-replace and ^, word boundary or look-behind operators Stephane Chazelas
2019-12-16 21:27 ` Stephane Chazelas
2019-12-17  7:38   ` Stephane Chazelas
2019-12-17 11:11     ` [PATCH] " Stephane Chazelas
2019-12-18  0:22       ` Daniel Shahaf
2019-12-18  8:31         ` Stephane Chazelas
2020-01-01 14:03         ` [PATCH v2] " Stephane Chazelas
2021-04-30  6:11           ` Stephane Chazelas
2021-04-30 23:13             ` Bart Schaefer
2021-05-05 11:45               ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2021-05-31  0:58                 ` Lawrence Velázquez
2021-05-31 18:18                 ` Bart Schaefer
2021-05-31 21:37                   ` [PATCH] (?) typeset array[position=index]=value Bart Schaefer
2021-06-01  5:32                     ` Stephane Chazelas
2021-06-01 16:05                       ` Bart Schaefer
2021-06-02  2:51                         ` [PATCH] (take two?) typeset array[position=index]=value / unset hash[$stuff] Bart Schaefer
2021-06-02 10:06                           ` Stephane Chazelas
2021-06-02 14:52                             ` Bart Schaefer
2021-06-02 16:02                               ` Stephane Chazelas
2021-06-02  9:11                         ` [PATCH] (?) typeset array[position=index]=value Stephane Chazelas
2021-06-02 13:34                           ` Daniel Shahaf
2021-06-02 14:20                             ` Stephane Chazelas
2021-06-02 15:59                               ` Bart Schaefer
2021-06-03  2:04                                 ` [PATCH (not final)] (take three?) unset "array[$anything]" Bart Schaefer
2021-06-03  2:42                                   ` Bart Schaefer
2021-06-03  6:12                                     ` Bart Schaefer
2021-06-03  8:54                                       ` Peter Stephenson
2021-06-03 13:13                                         ` Stephane Chazelas
2021-06-03 14:41                                           ` Peter Stephenson
2021-06-04 19:25                                             ` Bart Schaefer
2021-06-05 18:18                                               ` Peter Stephenson
2021-06-09 23:31                                                 ` Bart Schaefer
2021-06-13 16:51                                                   ` Peter Stephenson
2021-06-13 18:04                                                     ` Bart Schaefer
2021-06-13 19:48                                                       ` Peter Stephenson
2021-06-13 21:44                                                         ` Bart Schaefer
2021-06-14  7:19                                                           ` Stephane Chazelas [this message]
2021-06-03 18:12                                           ` Bart Schaefer
2021-06-04  8:02                                             ` Stephane Chazelas
2021-06-04 18:36                                               ` Bart Schaefer
2021-06-04 20:21                                                 ` Stephane Chazelas
2021-06-05  0:20                                                   ` Bart Schaefer
2021-06-05 17:05                                                     ` Stephane Chazelas
2021-06-10  0:14                                                       ` Square brackets in command position Bart Schaefer
2021-06-03  6:05                                   ` [PATCH (not final)] (take three?) unset "array[$anything]" Stephane Chazelas
2021-06-03  6:43                                     ` Bart Schaefer
2021-06-03  7:31                                       ` Stephane Chazelas
2021-06-10  0:21                         ` [PATCH] (?) typeset array[position=index]=value Bart Schaefer
2021-06-05  4:29                     ` Mikael Magnusson
2021-06-05  5:49                       ` Bart Schaefer
2021-06-05 11:06                         ` Mikael Magnusson
2021-06-05 16:22                           ` Bart Schaefer
2021-06-18 10:53                         ` Mikael Magnusson
2024-03-08 15:30                 ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2024-03-09  8:41                   ` [PATCH v5] " Stephane Chazelas
2024-03-09  9:21                     ` MBEGIN when =~ finds bytes inside characters (Was: [PATCH v5] regexp-replace and ^, word boundary or look-behind operators (and more).) Stephane Chazelas
2024-03-09 13:03                   ` [PATCH v3] regexp-replace and ^, word boundary or look-behind operators (and more) Stephane Chazelas
2024-03-10 19:52                     ` [PATCH v6] " Stephane Chazelas

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