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Re: Regex matching after ASCII characters

by suaveant (Parson)
on Oct 05, 2011 at 20:31 UTC ( #929876=note: print w/ replies, xml ) Need Help??

in reply to Regex matching after ASCII characters

$file =~ m{ \A [A-Z]{6} [A-Z0-9]{2} $prompt_host }xms; But it wouldn't be a bad idea to do some sanity checks on $prompt_host before randomly injecting user entered text into your regexp.

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Re^2: Regex matching after ASCII characters
by Anonymous Monk on Oct 05, 2011 at 21:11 UTC

    Thanks for your quick response, I tried your code and am getting the same false positives.

    Example: $prompt_host = "BR|GR", filenames such as: YUGRABCKFI01- and GRREPCCOBE10- are erroneously being pushed. Here is how I implemented your code:

    while (my $file = readdir(DIR)) { if($file =~ m{ \A [A-Z0-9]{8} $prompt_host }xms) { push(@traffic_file_list, $file); } }
      The problem with your code is the "BR|GR". Perl will now match any of these 2:
      \A [A-Z0-9]{8} BR
      The second one matches. The solution would be to set $prompt_host to:
      $prompt_host = (?:BR|GR)

        Perfect, thank you guys for your help.

      And with some sanity checking:

      >perl -wMstrict -le "my @t = ( 'YUGRABCKFI01-', 'GRREPCCOBE10-', ); ;; ENTRY: for my $entry ('BR|RG', 'FI', '(?{ `rm -R *` })', '++') { my $rx = eval { qr{ \A [A-Z]{6} [A-Z\d]{2} (?: $entry) }xms }; if ($@) { print qq{user entered '$entry' is evil: $@}; next ENTRY; } for my $t (@t, @ARGV) { printf qq{%7s %-3smatch with '$t' \n}, qq{'$entry'}, $t =~ $rx ? '' : 'NO' ; } } " "STTLWA02RG01_2011-10-" 'BR|RG' NO match with 'YUGRABCKFI01-' 'BR|RG' NO match with 'GRREPCCOBE10-' 'BR|RG' match with 'STTLWA02RG01_2011-10-' 'FI' match with 'YUGRABCKFI01-' 'FI' NO match with 'GRREPCCOBE10-' 'FI' NO match with 'STTLWA02RG01_2011-10-' user entered '(?{ `rm -R *` })' is evil: Eval-group not allowed at runtime, use re 'eval' in regex m/ \A [A-Z]{6} [A-Z\d]{2} (?: (?{ `rm -R *` })) / at ... user entered '++' is evil: Quantifier follows nothing in regex; marked by <-- HERE in m/ \A [A-Z]{6} [A-Z\d]{2} (?: + <-- HERE +) / at ...

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