Re: Using regexp with binary data

People attacking binary data with regular expressions generally have two problems: by default, /./ won't match newlines, and /$/ will, on a string which ends with character 10, match just before the final character.

The solution to the first of these problems is to use the s modifier on your regexp, as has already been mentioned. Note that you can encode this modifier into the regexp when you define it:

my $data = "\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11";

my @find = (
  # These Work
  qr"\x04\x05\x06\x07\x08\x09\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11"s,
  qr"\x04\x05.{4}\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11"s,
  qr"\x04\x05\x06\x07\x08.{1}\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11"s,
  qr"\x04\x05\x06\x07\x08\x09\x0a.{1}\x0c\x0d\x0e\x0f\x10\x11"s,

  #These didn't work before, but do now.
  qr"\x04\x05.{5}\x0b\x0c\x0d\x0e\x0f\x10\x11"s,
  qr"\x04\x05\x06\x07\x08\x09.{1}\x0b\x0c\x0d\x0e\x0f\x10\x11"s,
);

foreach (@find) {
  if ($data =~ /$_/) { print "found\n" } else { print "not found\n" } 
+;
};
[download]

The solution to the second problem is to use \Z instead of $ when you absolutely need the very end of the string, even if it ends in a newline.

As for online regexp references, doing perldoc perlre as suggested before is good (if you are working on windows and have ActiveState's perl installed, then search C:\Perl\html\index.html for "perlre") - if you prefer to look at some online page, googling for perlre will get you several online copies of the same page.

@/=map{[/./g]}qw/.h_nJ Xapou cets krht ele_ r_ra/;
map{y/X_/\n /;print}map{pop@$_}@/for@/
[download]

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Re^2: Using regexp with binary data by Anonymous Monk on Aug 28, 2005 at 16:06 UTC
Thanks for your help everyone. It is greatly appriciated. Its things like qr"\x04\x05.{4}\x0a\x0b\x0c\x0d\x0e\x0f\x10\x11"s that make me really love perl. I mean that is just poetry in programming right there.	[reply]