[Melbourne-pm] CPAN module
scottp at dd.com.au
Wed Mar 15 01:48:51 PST 2006
On 15/03/2006, at 20:29, Rick Measham wrote:
> Scott Penrose wrote:
>> CPAN & Debian are virtually identical, as is all Package
>> Management systems.
> I'd disagree here, but am happy to be wrong.
> With apt you can have many repository sources, they are all
> searched for the highest-version number when you ask to install a
> given package.
You are agreeing with me :-)
> With CPAN.pm you give it a list of repositories, but that's only
> for high-availability. The module gets an up-to-date module list
> from the first repository that is willing to give it. Recently the
> repository I've been using here in .au stopped updating and so I
> had no new sources since December 18th. CPAN.pm gave me a warning,
> but didn't bother checking any other mirror for a more up-to-date
Yes sort of. But APT is not a package management system, I wrote that
wrong, that is dpkg - APT is a repository management system really -
all about multiple repositories. (this is an oversimplification and
they run together).
This discussion has been confusing because everyone is mixing their
CPAN - is a single repository - like Debian.org - not Debian the
system, not debians package management system DPKG, not the APT
system for getting multiple repositories downloaded etc etc.
CPAN.pm - is a system for accessing that repository - and it is like
the old DPKG download system dselect - which was used before APT - it
was not very flexible.
> When I ask to install a module that list is considered canonical.
> CPAN.pm does not check any other repository for any other version.
> You cannot set up a new CPAN repository with a single module and
> put that at the top of your urllist, and have all other modules
> installed from the second preference.
> Many apologies if I'm wrong :)
Sort of. CPAN itself is for accessing CPAN. And CPAN is not a System
like APT, which is designed to have multiple repositories. CPAN IS
the repository. It is like having a repository (in debian anyway)
called "debian-unofficial" - that is the name of the repository. The
name of the CPAN repository is CPAN.
Package management systems are usually broken up into three things.
1) The repository - of which you can have many
2) The collection system (not sure of the right name for this thing)
- of which you can have many
eg: apt is one for Debian which works with others in concurrency
3) The package management/install system - there must be only one of
In Debian these are:
1) (simplified) debian.org, debian-unofficial.org, cdrom, etc
2) apt, dselect, (there used to be heaps others but apt is so good we
just use that now)
In Perl these are usually:
1) CPAN & Manually installed
2) CPAN (only really works with CPAN, but see previous post for
alternatives) & Manual
3) Perl Modules (it is self managed and can even have multiple
versions installed at once)
But of course this is an over simplification - what about APT &
Debian - they too can install Perl Modules.
So to answer Mathew's original question - he can use APT or GenToo or
RPM or MakeUpYourOwnModule or the CPAN modules I mentioned to manage
But... that is not CPAN.
So Rick - yes you are right CPAN is really the repository and it
comes with a free tool to get stuff - but people have extended it to
be both part 1 and part 2 - but what matters is part 3 - and you can
have multiple concurrent paths to part 3.
CPAN - Comprehensive Perl Archive Network - NOT a package management
system - a repository.
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scottp at dd.com.au
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