Re: URL to source file

[Vincent Lefevre <vincent@vinc17.net>]

On 2021-01-28 08:07:51 -0500, Greg Wooledge wrote:
> On Thu, Jan 28, 2021 at 02:26:47AM +0100, Vincent Lefevre wrote:
> >   print -r ${${(M)${(f)"$(aptitude show units)"}:#Version:*}#* }
> 
> I have one major objection to this: how do you handle a package that
> has more than one version available?
> 
> unicorn:~$ apt-cache show firefox-esr | grep ^Version:
> Version: 78.7.0esr-1~deb10u1
> Version: 78.5.0esr-1~deb10u1

The units package has 2 versions available:

zira:~> apt-cache show units | grep "^Version:"
Version: 2.21-1
Version: 2.18-1

but "aptitude show units" only returns one of them (the preferred one,
I suppose). So, no issues with my code.

In my previous message, I also gave the equivalent with apt-cache,
by using the --no-all-versions option.

[...]
> One of the advantages of this version over the zsh version is that it
> doesn't need to read the whole output of aptitude into memory all at
> once.

Note that with zsh, one can also do a process substitution. However,
I would tend to say that process substitution is more complex and
would have more overhead. At least there are more system calls with
bash:

zira:~> strace -f -o str.out bash -c 'v=$(date)' ; wc -l str.out
471 str.out

zira:~> strace -f -o str.out bash -c ': < <(date)' ; wc -l str.out
535 str.out

So I would say that command substitution is here more efficient.

Not much difference with zsh, though:

zira:~> strace -f -o str.out zsh -fc 'v=$(date)' ; wc -l str.out
725 str.out

zira:~> strace -f -o str.out zsh -fc ': < <(date)' ; wc -l str.out
726 str.out

-- 
Vincent Lefèvre <vincent@vinc17.net> - Web: <https://www.vinc17.net/>
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Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)