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Re: [patch #10070] toggle invert flag when reading `!'

From: Chet Ramey
Subject: Re: [patch #10070] toggle invert flag when reading `!'
Date: Thu, 27 May 2021 11:37:48 -0400
User-agent: Mozilla/5.0 (Macintosh; Intel Mac OS X 10.15; rv:78.0) Gecko/20100101 Thunderbird/78.10.2

On 5/27/21 11:20 AM, Andreas Schwab wrote:
On Mai 27 2021, Chet Ramey wrote:

On 5/26/21 9:55 PM, Dale R. Worley wrote:

    $ ! ! [ 1 -eq 1 ]; echo $?
That last one isn't defined by the manual page.  I'm surprised you don't
get a syntax error.

It's clearly valid.

According to the POSIX grammar, a pipeline can only be a pipe_sequence
optionally preceded by a single Bang.  If you want another Bang the
pipe_sequnce needs to be either a subshell or a brace_group.

True, but bash accepts it. (So do ksh and mksh; dash and yash do not.)

``The lyf so short, the craft so long to lerne.'' - Chaucer
                 ``Ars longa, vita brevis'' - Hippocrates
Chet Ramey, UTech, CWRU    chet@case.edu    http://tiswww.cwru.edu/~chet/

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