declaring a hash table in one file and using it in another in Perl

Question

I need to create a hash table in one file and use in in another. The reason for it is that that the table is my \"database\" and will be changed, and I want it to seat with

Answer 1

Define your hashtable in a global or package variable. Then use the do command to load the definition into another script:

 datafiles/database.def
 ---------------------------
 package ProjectData;
 our %DATA = ('abc' => 'def', 'ghi' => 'jkl', ...);


 scripts/myscript.pl
 ------------------------
 use strict;
 do 'datafiles/database.def';
 ... do something with %ProjectData::DATA ...

Answer 2

This is likely not be the best solution, but you could just use Storable or Data::Dumper, both of which are in the core since forever (5.7.3 and 5.5, respectively).

Alternatively, you could put them in another module and use/require that, ala

package MyImportantHash;

use Exporter;

our @EXPORT = qw( %important_hash );

our %important_hash = (
              some_key  => 'some_value',
         );

1;

And in your main package,

use MyImportantHash;
say "$_ => $important_hash{$_}" for sort keys %important_hash;

Of course, this all assumes that you don't want changes in the hash while in-memory to automatically show up in the file. If you do, look no further than davorg's answer.

Answer 3

There are too many ways to do it!

A simple one is to write your data to a file as CSV and load it using Text::CSV or Text::CSV_XS.

update:

You can also use the do builtin to read and execute a perl file from another script. I.e.:

do "config.pl";

Or use a configuration file format that allows for complex data structures (XML, JSON, yaml, .ini, etc.).

Answer 4

Perhaps you're looking for a tied hash.