Regular Expression problem when Extracting Start\ VALUE \End

gasho has asked for the wisdom of the Perl Monks concerning the following question:

I am trying to come up with universal code :) that will extract value between $StartTag value $EndTag from single line. I am having problem when special characters are involved.

my $line = <DATA>;
my @wanted_substrings=();
#No Problem
#my $StartTag='START';
#my $EndTag='END';

#Error Unmatched ) in regex; marked by <-- HERE in m/TRicky\(.*?)
#my $StartTag="TRicky\\";
#my $EndTag="\\endTricky";

#No Error but no value VALUE
#my $StartTag="Next\$";
#my $EndTag="\^Next";

#No Error but no value VALUE
my $StartTag="Last\+";
my $EndTag="\+some";
       if ($line=~/$StartTag(.*?)$EndTag/g)
    {
       push(@wanted_substrings,$1) ;

       }
print join "\n", @wanted_substrings;
__DATA__
CharSTARTanotherENDCharTRicky\VALUEE\endTrickyNext$VALUE^NextLast+VALU
+E+some
[download]

#Forgot to mention if I do not use $StartTag or $EndTag
# and insted use actual string that it will work.

#Instead
       if ($line=~/$StartTag(.*?)$EndTag/g)
#This one works
       if ($line=~/TRicky\\(.*?)\\endTricky/g)
#Problem is that I have to use varialble $ because 
#I am using it as an arg in my sub

sub getInfoFromSingleLineMultiLineFile
{
#$stag,$etag uses as arguments
    my ($InputFile,$stag,$etag)=@_;
    my ($line,@wanted_substrings);

    #Openning file for reading
    open(IFH,"$InputFile") || die "Can't open file: $InputFile\n";
      while($line=<IFH>)
      {
        if ($line =~ m/$stag(.*?)$etag/g)
        {
           push(@wanted_substrings,$1);
        }
      }
return @wanted_substrings;
}
[download]

Thanks in advance Gasho

Comment on Regular Expression problem when Extracting Start\ VALUE \End Select or Download Code

Replies are listed 'Best First'.
Re: Regular Expression problem when Extracting Start\ VALUE \End by japhy (Canon) on Sep 30, 2005 at 14:35 UTC
Backslashes are a pain in the back. Slash. The problem is that your regex ends up being `/TRicky\(.?)\endTricky/` because your variables interpolate. When that gets compiled as a regex, it's a problem because the trailing backslash of "TRicky\" has escaped the opening parenthesis. I would suggest using `my $StartTag = qr/TRicky\\/; my $EndTag = qr/\\endTricky/;` The qr// operator will keep things properly backslashed later, because the content is treated like a regex. Jeff `japhy` Pinyan, P.L., P.M., P.O.D, X.S.: Perl, regex, and `perl` hacker How can we ever be the sold short or the cheated, we who for every service have long ago been overpaid? ~~ Meister Eckhart*	[reply] [d/l] [select]
Re: Regular Expression problem when Extracting Start\ VALUE \End by gasho (Beadle) on Sep 30, 2005 at 15:50 UTC
Thank you all for quick responses `#Works fine my $StartTag = qr/TRicky\\/; my $EndTag = qr/\\endTricky/;` [download]	[reply] [d/l]
Re: Regular Expression problem when Extracting Start\ VALUE \End by philcrow (Priest) on Sep 30, 2005 at 14:31 UTC
Why not just make sure the string is a single line (say with split) then use extract_tagged from Text::Balanced. Unless you are just trying to teach yourself regexes, this module is ideal. Phil	[reply]
Re: Regular Expression problem when Extracting Start\ VALUE \End by gasho (Beadle) on Sep 30, 2005 at 16:36 UTC
I got an error when tried to use Text::Balanced I verified that I have Balanced.pm under /lib/Text Thanks `use Text::Balanced; $text='blabla<Else><LogEntry message="FAIL TESTCASE "/><FailTestCase/> +</Else>blabla'; ($extracted, $remainder) = extract_tagged($text); print $extracted; #Error #Undefined subroutine &main::extract_bracketed called at C:\InstallV3\ +Test.pl` [download]	[reply] [d/l]
Re^2: Regular Expression problem when Extracting Start\ VALUE \End by philcrow (Priest) on Sep 30, 2005 at 18:12 UTC
Text::Balances does not export functions into the main namespace by default. This means you have two options. First, you could ask for the function by name: `use Text::Balanced qw( extract_tagged ); # The rest of your code from above here.` [download] This will bring extract_tagged into your module's namespace. Alternatively, you could fully qualify the name: `use Text::Balanced; my $text = 'sometexthere'; ($extracted, $remainder) = Text::Balanced::extract_tagged($text);` [download] Phil	[reply] [d/l] [select]
Re^3: Regular Expression problem when Extracting Start\ VALUE \End by gasho (Beadle) on Sep 30, 2005 at 20:36 UTC
Re^4: Regular Expression problem when Extracting Start\ VALUE \End by philcrow (Priest) on Sep 30, 2005 at 21:00 UTC
Re^3: Regular Expression problem when Extracting Start\ VALUE \End by Anonymous Monk on Feb 12, 2015 at 23:20 UTC
Re^4: Regular Expression problem when Extracting Start\ VALUE \End by Anonymous Monk on Feb 13, 2015 at 07:43 UTC
Re: Regular Expression problem when Extracting Start\ VALUE \End by salva (Canon) on Sep 30, 2005 at 14:41 UTC
use `quotemeta` to escape special regex chars on the start and end strings: `my $StartTag = quotemeta("Last+"); my $EndTag = quotemeta("+some");` [download]	[reply] [d/l] [select]
Re: Regular Expression problem when Extracting Start\ VALUE \End by injunjoel (Priest) on Sep 30, 2005 at 17:15 UTC
Greetings all, In the spirit of TIMTOWTDI my suggestion is to use \Q\E. `sub getInfoFromSingleLineMultiLineFile { #args and file opening... while($line = <IFH>){ if($line =~ /\Q$stag\E(.*?)\Q$etag\E/){ push(@wanted_substrings,$1); } } return @wanted_substrings; }` [download] That should get you what you want. -InjunJoel "I do not feel obliged to believe that the same God who endowed us with sense, reason and intellect has intended us to forego their use." -Galileo	[reply] [d/l]


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