Re: [PATCH v9] scripts/bash_aliases: Add useful functions

Stefan Puiu
2021-03-01T10:23:34Z

Hi Alejandro,

On Sat, Feb 27, 2021 at 7:16 PM Alejandro Colomar (man-pages)
<alx.manpages@gmail.com> wrote:
[...snip]
> >> + find * -type f \
> >> + |grep '\.c$' \
> >> + |sort -V \
> >> + |xargs pcregrep -Mn "(?s)^\w*SYSCALL_DEFINE.\(${1},.*?\)" \
> >> + |sed -E 's/^[^:]+:[0-9]+:/&\n/';
> >> +
> >> + find * -type f \
> >> + |grep '\.[ch]$' \
> >
> > Any reason not to use "find . -type f -name '*.[ch]'" when you need to
> > restrict the files you're looking at? I would expect that to be
> > faster.
>
> I don't like find syntax. I never remember how all of its options work.
> grep is much simpler, and everyone knows how it works.
>
> find has: -[i]lname, -[i]name, -[i]path, -[i]regex, -[i]wholename
> I don't want to be reading the manual for all of them each time I use
> find. grep does the same with optional -i and some simple regex which
> anyone could understand with some basic regex knowledge.

I've always used find -name, I think most of the time it's enough. But
I can understand that people might prefer writing certain snippets in
a certain way, and you need to be comfortable with scripts you are
maintaining.

>
> For the performance part, I don't know; but we might be surprised. At
> most it might be a bit faster (nothing like 200%), but I care more about
> readability.

Actually, as far as I can tell there's not much difference
performance-wise between the two, as far as I can tell. At least when
searching the kernel source on my Linux VM. So it seems I'm wrong on
that point:

stefan@spuiu-vm:~/rpmbuild/BUILD/kernel-3.10.0-1160.2.2.el7/linux-3.10.0-1160.2.2.el7.x86_64$
time ( find . | grep '\.c' &>/dev/null )

real 0m0.076s
user 0m0.031s
sys 0m0.046s
stefan@spuiu-vm:~/rpmbuild/BUILD/kernel-3.10.0-1160.2.2.el7/linux-3.10.0-1160.2.2.el7.x86_64$
time ( find . -name '*.c' &>/dev/null )

real 0m0.088s
user 0m0.016s
sys 0m0.066s

>
> I also avoid using find -exec option, and instead use xargs. It's way
> simpler to understand, at least for me.
>
> See also:
> <http://doc.cat-v.org/unix/find-history>
> <http://harmful.cat-v.org/cat-v/>

Well, I understand the sentiment in those texts, but I would argue
that finding files by name is a core functionality of find :). It's
true that other extra functionality might not be exactly warranted,
and yes, '-print' feels kind of weird.

Thanks for bearing with me,
Stefan.