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IP addresses?

by phroggy (Monk)
on Aug 18, 2005 at 02:22 UTC ( #484657=obfuscated: print w/ replies, xml ) Need Help??

It occurred to me that a mostly-deobfuscated version of a previous JAPH I did still seems pretty odd. Top of page 68 in the camel book, if you're confused...
#!/usr/bin/perl use strict; use warnings; my @ips=( 74.117.115.116, 32.97.110.111, 116.104.101.114, 32.80.101.114, 108.32.104.97, 99.107.101.114, 44.32.32.10, ); print for @ips;

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Re: IP addresses?
by 5mi11er (Deacon) on Aug 18, 2005 at 14:32 UTC
    Interesting. So, what exactly is perl doing?
      DB<11> p 74.117.115.116;
    Just
      DB<12> p 74;
    74
      DB<13> p 74.117;
    74.117
      DB<14> p 74.117.115;
    Jus
      DB<15> p 74.117.32.32.44.115;
    Ju  ,s
    
    The dot operator is used to concatenate strings together, so as long as it doesn't look like a normal integer or floating point number, it assumes they are "strings", and perl is storing them as single byte integers (characters), rather than, for example, the string "74". When printed, out come their ascii representations.

    Is this a good description of what's going on internally, or is there some further magic to be explained?

    -Scott

      Good observations, but your guesses are completely wrong. See "Version Strings" in perldoc perldata. Looks like support for these is going away after 5.8...

      perl -e '($,,@_)=("er",",\n","l Hack"," P","Just anoth"); print reverse @_;'
        Ah, version strings. I'd forgotten about those.

        It's a nice side effect that "raw" IP addresses end up getting stored like that.

        But, is it portable between big and little endian machines?

        -Scott

Re: IP addresses?
by cristian (Hermit) on Aug 18, 2005 at 14:59 UTC
    Simply Example 1: without "for" my @ips=( 74.117.115.116, 32.97.110.111, 116.104.101.114, 32.80.101.114, 108.32.104.97, 99.107.101.114, 44.32.32.10, ); print @ips; Example 2: whithout @ips print ( 74.117.115.116, 32.97.110.111, 116.104.101.114, 32.80.101.114, 108.32.104.97, 99.107.101.114, 44.32.32.10, ); This is the end. Just another Perl hacker,
      Ahh, good call - I hadn't thought of removing "for". As for removing @ips, I thought leaving it in would add just a tiny bit of misdirection, making the reader think of IP addresses....

      perl -e '($,,@_)=("er",",\n","l Hack"," P","Just anoth"); print reverse @_;'

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