l i n u x - u s e r s - g r o u p - o f - d a v i s
Next Meeting:
July 7: Social gathering
Next Installfest:
Latest News:
Jun. 14: June LUGOD meeting cancelled
Page last updated:
2001 Dec 30 17:06

The following is an archive of a post made to our 'vox-tech mailing list' by one of its subscribers.

Report this post as spam:

(Enter your email address)
Re: [vox-tech] howto: perl modules and global variables
[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]

Re: [vox-tech] howto: perl modules and global variables

On Thu, Jun 14, 2001 at 08:56:30AM -0700, Peter Jay Salzman wrote:
> i'm trying to figure out how a perl module accesses a global variable.
> below i show listings for the module (Hello.pm) and the program
> (testmodule.pl).  testmodule defines a global variable which i'd like
> to know how to access from within Hello.pm.
> anyone know how to do this?

Your code almost works; see below for my coments.

> Hello.pm:
>        package Hello;
>        require Exporter;          # } These set up an import
>        @ISA = qw(Exporter);       # } method, called implicitly
>        @EXPORT = qw( say_hello ); # } by use().
>        sub say_hello {
>           print "Hello, world!\n";
>           print $globalvariable . "\n";

$globalvariable is uninitialized but is a ``global''.[1]

>        }
>        return 1;
> testmodule.pl:
>       #!/usr/bin/perl -w
>       use diagnostics;
>       use Hello;
>       my $globalvariable = "hello world";

This $globalvariable is NOT a global. It is a lexical. The $globalvariable
referenced earlier is quite seperate. 

>       print "using scope specifier:\n";
>       Hello::say_hello();
>       print "now without scope specifier:\n";
>       say_hello();

[1] Quotes around global because perl does not really have globals per se.
All variables are associated with some namespace. Variables in the default
namespace mail can be treated as globals in most cases.

Henry House
OpenPGP key available from http://romana.hajhouse.org/hajhouse.asc

LUGOD Group on LinkedIn
Sign up for LUGOD event announcements
Your email address:
LUGOD Group on Facebook
'Like' LUGOD on Facebook:

Hosting provided by:
Sunset Systems
Sunset Systems offers preconfigured Linux systems, remote system administration and custom software development.

LUGOD: Linux Users' Group of Davis
PO Box 2082, Davis, CA 95617
Contact Us

LUGOD is a 501(c)7 non-profit organization
based in Davis, California
and serving the Sacramento area.
"Linux" is a trademark of Linus Torvalds.

Sponsored in part by:
Appahost Applications
For a significant contribution towards our projector, and a generous donation to allow us to continue meeting at the Davis Library.