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

I have input lines that start with "./" and ".\",my regex works when the line starts with ".\" fails for the other one,I need help to write a regex that fits in both the scenarios? 

INPUT:-

.\amss\platform\cs\bin\cdep.exe-43041;FILE.flf;//deploy/core/cs/pk/rel
+/1.4/bin/cdep.exe - VU_CORE_CS_PK.01.04.00.07.00 : 5
./modem_proc/build/ms/dmss_flags.min-000197;FILE.flf;//depot/asic/buil
+d/ms/dmss_flags.txt - BUILD_MS.00.00.02 : 5

I have the following code which fails when the line starts with "./",h
+ow do I modify the below code to suit for both the above inputs?

OUTPUT:-
KEYS:-//deploy/core/cs/pk/rel/1.4/bin/cdep.exe
      //depot/asic/build/ms/dmss_flags.txt           
VALUES:- amss\platform\cs\bin\cdep.exe
         modem_proc/build/ms/dmss_flags.min

my %hash_basebuild_rpf; 
 
open my $inputfh, '<', $basebuild_rpf_file or die "could not open $bas
+ebuild_rpf_file - $!"; 
while (my $line = <$inputfh>) {  
    chomp($line);
    my ($key) = $line =~ /;([^;]+)\s-\s/;  
    print "KEY:$key\n";
    my ($value) = $line =~ /\.\\(.*);/; # this line fails when the lin
+e starts with "./"
    print "VALUE:$value\n";
  
    $hash_basebuild_rpf{$key} = $value unless (exists $hash_basebuild_
+rpf{$key}); 
}

[download]

Replies are listed 'Best First'.
Re: Regex failing when the line starts with "./"
by davido (Cardinal) on Feb 03, 2011 at 09:38 UTC

    Maybe the faulty line should read as follows:

    my( $value ) =
    $line =~ m{(?:\.\\|\./)(.*);};

    [download]

    (Re updated to correct the order of dot and slash)

    Match either '.\' or '/.' followed by everything up to and including ';'. Note, I used '{' and '}' curly brackets to improve legibility. It's bad enough with all those \'s and /'s. I also used non-capturing (?:....) brackets in constraining the alternation so that the capturing brackets used later on in the same RE would retain their position as $1.


    Dave

[reply]
[d/l]
      I'm trying to wrap my head around this and it's not coming together.
      Wouldn't (?:\.\\|\./) mean "full stop, then either backslash or dot, then forward slash"?
      I have no time to test this now, but it seems to me that the correct regex would be:
      $line =~ m{(?:\.\\)|(?:\./)(.*);};
      with grouping on either side of the |. Or does a | placed within grouping parentheses always match the entire first/second half of the grouping?
[reply]
[d/l]
[select]
        Wouldn't (?:\.\\|\./) mean "full stop, then either backslash or dot, then forward slash"? ... Or does a | placed within grouping parentheses always match the entire first/second half of the grouping?

        It is second case: [.\\] is one group of regex, [./] is the other.

        To match per your first query, regex would be qr{[.] (?: \\ | . ) /}x (which I would rather write as qr{[.] [.\\] /}x but that is besides the point).

[reply]
[d/l]
[select]
Re: Regex failing when the line starts with "./"
by tospo (Hermit) on Feb 03, 2011 at 09:40 UTC
    try 
    my ($value) = $line =~ /\.[\\\/](.*);/;

    [download]
[reply]
[d/l]
      my ($value) = $line =~ /\.[\\\/](.*);/;

      [download]

      That won't match lines starting with '/.'

      Update: ./ /. \. .\.... too many dots and slashes. I got it wrong.

      :)


      Dave

[reply]
[d/l]
Re: Regex failing when the line starts with "./"
by Anonymous Monk on Feb 03, 2011 at 10:21 UTC
[reply]

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