Subject: Re: [PATCH] test-lib.sh: use awk instead of expr for a POSIX non integer check

From: Junio C Hamano <[email-masked]>
Date: Wed, 09 Mar 2022 09:47:33 -0800

Eric Sunshine <[email-masked]> writes:

> On Tue, Mar 8, 2022 at 6:58 PM Eric Sunshine <[email-masked]> wrote:
>> On Tue, Mar 8, 2022 at 6:55 PM Eric Sunshine <[email-masked]> wrote:
>> > On Tue, Mar 8, 2022 at 6:44 PM Carlo Marcelo Arenas Belón
>> > <[email-masked]> wrote:
>> > > +               local _GLIBC_VERSION=$(getconf GNU_LIBC_VERSION 2>/dev/null)
>> > > +               if echo "$_GLIBC_VERSION" | cut -d. -f1-2 |
>> > > +                       awk '{ if ($2 - 2.34 < 0) exit 1 }'
>> >
>> > No need for `cut` since `awk` can accomplish the same by itself.
>> >
>> >     if echo "$_GLIBC_VERSION" | awk '/^glibc / { if ($2 - 2.34 < 0) exit 1 }'
>> >
>> > should work, I would think.
>>
>> Nevermind, I forgot you want to better support "2.34.9000" matches.
>> Though, awk should still be able to do so on its own, one would
>> expect, but not too important.
>
> This seems to work, though it's getting a bit verbose:
>
>     awk '/^glibc / { split($2,v,"."); if (sprintf("%s.%s", v[1], v[2])
> - 2.34 < 0) exit 1 }'

If we are losing "cut" (which I think is a good thing to do), we
probably can lose the pipe, too and refer to $_GLIBC_VERSION as an
element in ARGV[] and make the command used as "if" condition to a
single "awk" script?

In general it is a good discipline to question a pipeline that
preprocesses input fed to a script written in a language with full
programming power like awk and perl (and to lessor extent, sed) to
see if we can come up with a simpler solution without pipeline
helping to solve what these languages are invented to solve, and I
very much appreciate your exploration ;-)

Thanks.