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Re: Arithmetic expansion with increments and output redirection
From: |
Andreas Schwab |
Subject: |
Re: Arithmetic expansion with increments and output redirection |
Date: |
Wed, 24 Apr 2019 15:07:53 +0200 |
User-agent: |
Gnus/5.13 (Gnus v5.13) Emacs/26.2 (gnu/linux) |
On Apr 24 2019, Greg Wooledge <address@hidden> wrote:
> On Wed, Apr 24, 2019 at 06:47:41AM -0600, Ian Neal wrote:
>> At what point is a subshell being invoked? There's no pipeline, command
>> substitution, coprocess, background process, or explicit () subshell here,
>> which are the only cases a subshell should be created. Otherwise, the
>> entire operation should be evaluated by the main shell. Arithmetic
>> expansion is not in that list.
>
> The context got snipped but IIRC it was something like
>
> /bin/true > $((n++))
>
> The /bin/true forces the use of an external command, which means a subshell
> is forked. The redirection occurs in the forked subshell.
But the expansion isn't required to be performed in the subshell. I
don't see POSIX having any wording to require one or the other. Doing
the expansion before the fork looks reasonable, even if only to make it
consistent with builtins.
Andreas.
--
Andreas Schwab, address@hidden
GPG Key fingerprint = 7578 EB47 D4E5 4D69 2510 2552 DF73 E780 A9DA AEC1
"And now for something completely different."
- Arithmetic expansion with increments and output redirection, Ian Neal, 2019/04/23
- Re: Arithmetic expansion with increments and output redirection, Robert Elz, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Ian Neal, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Greg Wooledge, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection,
Andreas Schwab <=
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Ian Neal, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Ilkka Virta, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Greg Wooledge, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Ian Neal, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24
- Re: Arithmetic expansion with increments and output redirection, Chet Ramey, 2019/04/24