Question

I’m trying to put a hash %listvol into an array @fileInfo in Perl.

@fileInfo = ($filename, $data, $index, \%listvol);

%listvol contains a list of volume: key = $vol, value = $vol.
The first $vol values are ABCDEF, then GFFFF, EEEAA – always different.

Then I put the array @fileInfo in the hash %listeAllFile:

$listeAllFile{$nameOfFile} = [@fileInfo];

Later I’m trying to get the hash %listvol without success. I’m using this code:

foreach $key (keys %listeAllFile) {
    @tab      = @{ $listeAllFile{$key} };
    $filename = $tab[0];
    %listvol  = %{ $tab[3] };
    foreach $vol (keys %listvol) {
        print "\n vol is $vol for file $filename";
    }

The file name is always different, so it is ok. But the value of the variable $vol is always the same, ABCDEF. It seems that I get get each time the same value.

Does anyone have an idea?

Answer 1

While you didn’t include code to reproduce your problem, I’m fairly sure that the issue is that you’re storing a reference to the same %listvol hash in each array.

When you change the contents of %listvol for the second entry, you’re modifying the first entry at the same time. One way to fix that is to use {%listvol} instead of \%listvol. The former makes a shallow copy of the current contents of %listvol, just like [@fileInfo] makes a shallow copy of the current contents of @fileInfo.