CPAN install nightmare
mkpm-20051014 at djce.org.uk
Mon Mar 27 12:52:18 PST 2006
On Mon, Mar 27, 2006 at 09:27:01PM +0100, Ian Cameron wrote:
Easy questions first.
> How is the location of installed modules decided?
Each installation of Perl has a whole bunch of "Config" values (which were
chosen when perl was built), including things such as where to install
modules, where to install `bin' or `sbin' files, etc. For example, try typing
`perl -V:sitearch' to see where (IIRC) CPAN will tend to install modules.
> How does Perl know where to look for them?
Each `perl' executable has a compiled-in default search path. Type
`/path/to/perl -V' to see the default list.
> Can modules installed under each setup be used together, and if so how?
Sometimes (in fact, usually). However, it's not usually a good idea.
You would do this by adding the extra directories to the lib search path, e.g.
using `perl -I ...' or `use lib ...'.
> The new perl is the one in /usr/local/bin, which is 5.8.8, the one in
> /usr/bin is 5.8.5 and came via the RHEL RPM's. I presume the 5.8.8 version
> was installed to satisfy a dependency when I installed one of the other
Sounds convincing. Sometimes a module will decide that it requires a
whole new version of Perl, so CPAN will "helpfully" download and install a new
Perl for you. And no, I've never found this to be a useful behaviour. :-(
Personally what I would do now is disregard the new perl (i.e. the one under
/usr/local), and try installing the modules you require using the packaged
perl. Beware: when you start CPAN (e.g. by typing 'cpan', or 'perl -MCPAN -eshell'),
make sure you type the full path to the correct perl / cpan.
"/usr/bin/perl -MCPAN -eshell"
will install things under your RPM'd perl, whereas
"/usr/local/bin/perl -MCPAN -eshell"
whill install things for your new /usr/local perl; whereas the behaviour of
"perl -MCPAN -eshell"
depends on which `perl` is in your $PATH first.
Did that make sense?
PGP key: http://rudolf.org.uk/pgpkey
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