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Re: Extracting IP addresses from a file...

by damian1301 (Curate)
on Jul 04, 2001 at 23:38 UTC ( #93922=note: print w/ replies, xml ) Need Help??

in reply to Extracting IP addresses from a file...

foreach($data=~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g){ push @ips, $1; }
Should do it. (or some re like that.)

$_.=($=+(6<<1));print(chr(my$a=$_));$^H=$_+$_;$_=$^H; print chr($_-39); # Easy but its ok.

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Re: Re: Extracting IP addresses from a file...
by tachyon (Chancellor) on Jul 05, 2001 at 00:02 UTC

    You can't use foreach like this - you need to use while to make your code work. See the code below for a demo:

    $data = <<'DATA'; foo foo bar bar baz 333.333.333.333 baz DATA # this is *wrong* foreach($data=~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g){ push @ips, $1; } print "Foreach fails and gives:\n"; print "$_\n" for @ips; @ips = (); # this is right while($data=~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g){ push @ips, $1; } print "While works and gives:\n"; print "$_\n" for @ips;

    For an explanation of why the for loop generates three copies of the last IP address you need to consider what has happened. A /g type regex will return an array of matches. So as it is called in array context it returns an array (this actually contains the three addresses) however $1 now contains the last address matched as we had to match all occurences to generate the array. We then iterate over this array and push $1 (the last IP address) into our array three times. To fix this we either use while or push $_ (not $1) into our IP array like this:

    $data = <<'DATA'; foo foo bar bar baz 333.333.333.333 baz DATA foreach($data=~ /(\d{1,3}\.\d{1,3}\.\d{1,3}\.\d{1,3})/g){ push @ips, $_; } print "Foreach now gives:\n"; print "$_\n" for @ips;

    Oh you can slurp up the file into a variable $data like this:

    open FILE, "<path/to/file" or die "Oops, Perl says: $!"; { local $/; $data = <FILE>; } close FILE;




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