Hi,

I'm coding some logging configuration info into hash of hashes - for instance: 
my %Log_names = (
               "BM_therm_boiler_00_state"  => { 'events_log' => 1 },
               "BM_therm_house_00_state"  => { 'events_log' => 1 },
               "BM_therm_hpump_00_state"  => { 'events_log' => 1 },
               "BM_swi_"  => { 'device_log' => 1 },
              );

[download]


Now I'd like to check for certain key whether it exists and retrieve it's content. But using simple exists or defined with double hashes, like 
if exists $Log_names{"BM_light_test_00_"}{"device_log"}

[download]
I get the right result but it seems that keys are added to hash. Can I prevent this ?

$VAR1 = {
          'BM_light_test_00_' => {},
          'BM_swi_' => {
                         'device_log' => 1
                       },
          'BM_therm_house_00_state' => {
                                         'events_log' => 1
                                       },
          'BM_therm_boiler_00_state' => {
                                          'events_log' => 1
                                        },
          'BM_therm_hpump_00_state' => {
                                         'events_log' => 1
                                       }
        };

[download]
How to properly check existence and retrieve its content from hash of hashes ?

Thanks in advance,

regards,

Rob.

In reply to Checking existence in hash of hashes without adding entries by Anonymous Monk

Title:
Use:  <p> text here (a paragraph) </p>
and:  <code> code here </code>
to format your post, it's "PerlMonks-approved HTML":


  • Posts are HTML formatted. Put <p> </p> tags around your paragraphs. Put <code> </code> tags around your code and data!
  • Titles consisting of a single word are discouraged, and in most cases are disallowed outright.
  • Read Where should I post X? if you're not absolutely sure you're posting in the right place.
  • Please read these before you post! —
  • Posts may use any of the Perl Monks Approved HTML tags:
    a, abbr, b, big, blockquote, br, caption, center, col, colgroup, dd, del, details, div, dl, dt, em, font, h1, h2, h3, h4, h5, h6, hr, i, ins, li, ol, p, pre, readmore, small, span, spoiler, strike, strong, sub, summary, sup, table, tbody, td, tfoot, th, thead, tr, tt, u, ul, wbr
  • You may need to use entities for some characters, as follows. (Exception: Within code tags, you can put the characters literally.)
            For:     Use:
    & &amp;
    < &lt;
    > &gt;
    [ &#91;
    ] &#93;
  • Link using PerlMonks shortcuts! What shortcuts can I use for linking?
  • See Writeup Formatting Tips and other pages linked from there for more info.