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Re: Q on Bash's self-documented POSIX compliance...

From: John Kearney
Subject: Re: Q on Bash's self-documented POSIX compliance...
Date: Sun, 27 Jan 2013 04:52:20 +0100
User-agent: Mozilla/5.0 (Windows NT 6.1; WOW64; rv:17.0) Gecko/20130107 Thunderbird/17.0.2

Am 27.01.2013 01:37, schrieb Clark WANG:
> On Sat, Jan 26, 2013 at 1:27 PM, Linda Walsh <address@hidden> wrote:
>> I noted on the bash man page that it says it will start in posix
>> compliance mode when started as 'sh' (/bin/sh).
>> What does that mean about bash extensions like arrays and
>> use of [[]]?
>> Those are currently not-POSIX (but due to both Bash and Ksh having
>> them, some think that such features are part of POSIX now)...
>> If you operate in POSIX compliance mode, what guarantee is there that
>> you can take a script developed with bash, in POSIX compliance mode,
>> and run it under another POSIX compliant shell?
>> Is it such that Bash can run POSIX compliant scripts, BUT, cannot be
>> (easily) used to develop such, as there is no way to tell it to
>> only use POSIX?
>> If someone runs in POSIX mode, should bash keep arbitrary bash-specific
>> extensions enabled?
>> I am wondering about the rational, but also note that some people believe
>> they are running a POSIX compatible shell when they use /bin/sh, but would
>> get rudely surprised is another less feature-full shell were dropped in
>> as a replacement.
> I think every POSIX compatible shell has its own extensions so there's no
> guarantee that a script which works fine in shell A would still work in
> shell B even if both A and B are POSIX compatible unless the script writer
> only uses POSIX compatible features. Is there a pure POSIX shell without
> adding any extensions?
dash is normally a better gauge of how portable your script is, than
bash in posix mode.

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