[Buildroot] [PATCH] support/scripts/check-host-libs: add new check on host binaries/libs

[yann.morin at orange.com]

David, All,

On 2022-09-21 08:23 +0000, David Laight spake thusly:
> From: Arnout Vandecappelle
> > Sent: 20 September 2022 20:49
> ...
> > date +%s
> > find host/*bin host/lib* -type f |while read f; do
> >          if printf '\x7f\x45\x4c\x46' | cmp -s -n 4 - ${f}; then
> >              printf '%s\n' "${f}"
> >          fi
> > done | wc -l
> > date +%s
> > 
> > 1663702312
> > 111
> > 1663702338
> 
> Think a bit further and you can remove the exec of cmp, eg:
> 
> $ time find /usr/lib -type f | (ELF="$(printf '\x7f\x45\x4c\x46')"; while read f; do read l <"$f" && [ "${l#$ELF}" != "$l" ] && echo $f; done )| wc -l

Nice trick. That took ~3s on my host/ dir.

And then, I think we can do simpler and more obvious (we know we have
bash, so we can use the bashisms 'read -N'):

    read -N 4 magic <"${f}"
    if [ "${magic}" = "${ELF}" ]; then printf "%s\n" "${f}"; fi

Now it's about ~1s, and that yields the same list as cmp yields.

Regards,
Yann E. MORIN.

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