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 <vinc...@vinc17.net> - Web: <https://www.vinc17.net/>
100% accessible validated (X)HTML - Blog: <https://www.vinc17.net/blog/>
Work: CR INRIA - computer arithmetic / AriC project (LIP, ENS-Lyon)
