[pacman-dev] [PATCH] [makepkg] use double brackets

[Xavier Chantry]

On Tue, May 25, 2010 at 10:06 PM, Andres P <aepd87 at gmail.com> wrote:
> On Sat, May 22, 2010 at 2:18 AM, Allan McRae <allan at archlinux.org> wrote:
>> In fact, thinking about this more.  Bash-4.1 was released on 2010-01-03 so
>> it will have been out for ~6 months before the next pacman release. Anyone
>> upgrading their package manager from 3.3 -> 3.4 will upgrade bash from 4.0
>> -> 4.1 so this is probably a non-issue.
>>
>> So I will accept this patch when the comment above and "stray" ! is removed
>> with it.
>>
>> Allan
>>
> I was about to do that, but first I think I should talk about another
> change.
>
> `type -p foo` has a return val, so consider this:
>    $ time for i in {1..1000}; do [[ $(type -p sh) ]]; done
>    real    0m1.564s
>    user    0m0.160s
>    sys 0m0.337s
>
>    $ time for i in {1..1000}; do type -p sh &>/dev/null; done
>    real    0m0.166s
>    user    0m0.060s
>    sys 0m0.103s
>
> Even though there is a negligible perfomance difference in makepkg, this
> is the correct way to check for $?.
>

I don't understand this sentence.
negligible = 10x ?
And if your "correct" way is 10x faster, why do you say "even though" ?
This makes it sound like we need to accept a compromise (like worse
perf) for a correct behavior.
But from my understanding of your mail, you are saying that using type
-p directly is both more correct and faster.

> If the redir to /dev/null becomes to much of a burden to type, it could
> become a function. Not to mention that the whole series of checking
> for vcs in PATH, which is where most of `type p` gets used, could be
> changed in to a more platable chunk.
>
> Would there be interest in making this change?
>
> I really think that throwing away the return val and making a string
> check is poor practice.
>
>

So the only downside of using  type -p sh &>/dev/null directly without
[/[[ and a subshell is that we need to type &>/dev/null ?
It does not seem like a big deal to me.
And yeah if it's used a lot, like more than 5 times, just make a function.