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Re: [PATCH] tests: avoid problematic $(< file) shell construct

From: Pádraig Brady
Subject: Re: [PATCH] tests: avoid problematic $(< file) shell construct
Date: Mon, 16 Dec 2013 16:10:59 +0000
User-agent: Mozilla/5.0 (X11; Linux x86_64; rv:17.0) Gecko/20130110 Thunderbird/17.0.2

On 12/16/2013 02:53 PM, Bernhard Voelker wrote:
> On 12/16/2013 03:27 PM, Eric Blake wrote:
>> On 12/15/2013 12:59 PM, Bernhard Voelker wrote:
>>> +# Avoid problematic redirect-only statements in $(...) shell construct.
>>> +# Although the "man bash" states that this is faster, it does not seem
>>> +# to be portable.  Issues have been seen on dash v0.5.6 and on the shell
>>> +# on FreeBSD.
>>> +sc_prohibit_redirect_only_command_substitution:
>>> +   @prohibit='\$$\(<'              \
>> Shouldn't you also prevent $(> ...)?
> Maybe yes, but I don't think that it's use is very likely,
> because one wanting to create a file that way would most
> probably do it without the $(...) command substitution.
> The check is quite rough anyway because nothing prevents
> a user from writing a command after the redirection:
>   u="$(</etc/passwd  head -n1 | cut -d: -f1)"
> However, I think such use is very rare.

Well not really. You could easily have $(<file tr blah BLAH) for example.
While this could be reordered, I suppose the re should only match
there is no space or no | after the initial name.
I suppose we should also handle `< file`.


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