I have an application in which scripts will be run that need to be able access stored data. I want to run a script (main.pl) which will create an array. Later, if I run A.pl or B.pl, I want those scripts to be able access the previously created array and change values within it. What do I need to code in main.pl A.pl B.pl so I can achieve that?
2 Answers
Normally one perl instance can not access the variables of another instance. The question then becomes "what can one do that is almost like sharing variables"?
One approach is to store data somewhere it can persist, such as in a database or a CSV file on disk. This means reading the data at the beginning of the program, and writing it or updating it, and naturally leads to questions about race conditions, locking, etc... and greatly expands the scope that any possible answer would need to cover.
Another approach is to write your programs to use CSV or YAML or some other format easily read and written by libraries from CPAN, and use STDIN and STDOUT for input and output. This allows decoupling of storage, and also chaining several tools together with a pipe from the shell prompt.
For an in-memory solution for tieing hashes to shared memory, you can check out IPC::Shareable
Comments
Perl memory structures can't be stored and then accessed later by other Perl scripts. However, you can write out those memory structures as a file. This can be done through hard raw coding, or by using a wide variety of Perl modules. The Storable is a standard Perl module and has been around for quite a while.
Since all you're installing is an array, you could have one program write the array to a file, and then have the other file read the array.
use strict;
use warnings;
use autodie;
use constant {
ARRAY_FILE => "$Env{HOME}/perl_arry.txt",
};
my @array;
[...] #Build the array
open my $output_fh, ">", ARRAY_FILE;
while my $item ( @array ) {
say {$output_fh} $item;
}
close $output_fh;
Now, have your second program read in this array:
use strict;
use warnings;
use autodie;
use constant {
ARRAY_FILE => "$Env{HOME}/perl_arry.txt",
};
my @new_array;
open my $input_fh, "<", ARRAY_FILE;
while ( my $item = <$input_fh> ) {
push @new_array, $item;
}
close $input_fh;
More complex data can be stored with Storable, but's it's pretty much the same thing: You need to write Storable to a physical file and then reopen that file to pull in your data once again.
Comments
StorableorData::Dumpermodules