Need help in construct an regexp

Question

Need help in construct an regexp

whn (Programmer)

(OP)

28 Mar 13 15:57

I need to find a string match at Microsoft site. Out of its web page, there could be one or more strings look like this:

<a class="download" onclick="return false;" href="confirmation.aspx?id=36888" bi:fileurl="http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu"

var downloadFileUrl = "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu" ;

$("#ctl00_ctl21_ColumnRepeater_ctl00_RowRepeater_ctl01_CellRepeater_ctl00_ctl01").details({ "downloadUrl": "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu", "enableAtlasActionTag": true, "atlasActionTag": ""

The regexp I came up is somewhat like this:

CODE

my $kb = 'KB2809289';
my $pattern = qq/http:\/\/download\.microsoft\.com\/download([\\d+\\D+\\w+\W+]+)+$kb\.msu/;

I then have two implementations:

Implementation I:

CODE

my $pattern = qq/http:\/\/download\.microsoft\.com\/download([\\d+\\D+\\w+\W+]+)+$kbName\.msu/;
  my $contents = `cat $srce`; # The Microsoft page has been saved as a local file
  my $i = 1;
  while($contents =~ /($pattern)/g) {
    my $match = $&;
    print ("\$i = $i, $match\n");
    $i++;
  }

The error I got is like this:

CODE

Complex regular subexpression recursion limit (32766) exceeded at <file name> line 3348.

Implementation II:

CODE

if(open(FH, $srce)) {
    my $i = 1;
    while(my $line = <FH>) {
      if($line =~ /($pattern)/g) {
        my $match = $1;
        print ("\$i = $i, $match\n");
      }
      $i++;
    }
    close(FH);
  }

No match is found. So I know the regexp is incorrect.

Please help me in two areas:
1) fix my regexp;
2) with a correct regexp, would I still get this error - Complex regular subexpression recursion limit (32766) exceeded?

Many thanks!!

feherke (Programmer) · Answer 1 · 2013-03-29 06:43:24

Hi

What is the expected output for that sample input ?

Feherke.
http://feherke.github.com/

whn (Programmer) · Answer 2 · 2013-03-29 08:42:15

Sorry for not having myself clear.

I need to extract "ｈｔｔｐ：//download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu" from an html file. The strings in bold red font are known. A few sample lines in that html file were listed in my original post.

Thanks.

feherke (Programmer) · Answer 3 · 2013-03-29 08:53:44

Hi

Oops. I had the feeling you want only certain parts of the URLs.

Then I would do it like this :

CODE --> Perl

my $kb = 'KB2809289';
my $pattern1 = qq{http://download.microsoft.com/download.+?-$kb-\\w+.msu};    # string
my $pattern2 = qr{http://download\.microsoft\.com/download/.+?-$kb-\w+\.msu}; # regular expression

my $contents = do { local $/; <DATA> };

my $i = 1;
while ($contents =~ /$pattern1/g) {
  my $match = $&;
  print "\$i = $i, $match\n";
  $i++;
}

__DATA__
<a class="download" onclick="return false;" href="confirmation.aspx?id=36888" bi:fileurl="
http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu"

var downloadFileUrl = "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu" ;

$("#ctl00_ctl21_ColumnRepeater_ctl00_RowRepeater_ctl01_CellRepeater_ctl00_ctl01").details({ "downloadUrl": "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu", "enableAtlasActionTag": true, "atlasActionTag": ""

Note that using the $pattern1 string or the $pattern2 regular expression does the same. I included both as I see you mixed abit the their syntax.

Feherke.
http://feherke.github.com/

whn (Programmer) · Answer 4 · 2013-03-29 11:12:21

Thank you so much, Feherke! You are the man!!

whn (Programmer) · Answer 5 · 2013-03-29 12:42:11

Hi Feherke,

I have a follow-up question.

I modified your code a bit. Please also note that I modified the input data, too. All my changes are in blue bold fonts.

I noticed that when regexp is used, then the case-insensitive match would not work. Is this the way supposed to be?

Again, thank you so much for your help.

CODE

my $kb = 'KB2809289';
my $cpuType = 'x86'; # passed in, could be in upper case, too
my $cpuTypeInL = lc($cpuType);
my $cpuTypeInU = uc($cpuType);

# String
my $pattern1 = qq{http://download.microsoft.com/download.+?-$kb-$cpuTypeInL.*?.msu};
my $pattern2 = qq{http://download.microsoft.com/download.+?-$kb-$cpuTypeInU.*?.msu};

# regular expression
my $pattern3 = qr{http://download\.microsoft\.com/download/.+?-$kb-$cpuTypeInL.*?.msu};
my $pattern4 = qr{http://download\.microsoft\.com/download/.+?-$kb-$cpuTypeInU.*?.msu};

my $p;
#$p = $pattern1; # string match - match all 3
#$p = $pattern2; # string match - match all 3
#$p = $pattern3; # regexp match - only match 2
$p = $pattern4;  # regexp match - only match 1

my $contents = do { local $/; <DATA> };
if($p =~ /x86/) {
  print "Lower Case Pattern: $p\n";
}
else {
  print "Upper Case Pattern: $p\n";
}

my $i = 1;
while ($contents =~ /$p/gi) { # make it case-insensitive match
  my $match = $&;
  print "\$i = $i, $match\n";
  $i++;
}
__DATA__
<a class="download" onclick="return false;" href="confirmation.aspx?id=36888" bi:fileurl="
http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu"

var downloadFileUrl = "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-X86.msu" ; // It's upper case!!

$("#ctl00_ctl21_ColumnRepeater_ctl00_RowRepeater_ctl01_CellRepeater_ctl00_ctl01").details({ "downloadUrl": "http://download.microsoft.com/download/8/D/5/8D5F90F3-AC24-4A15-9716-BAE10533977A/Windows6.0-KB2809289-x86.msu", "enableAtlasActionTag": true, "atlasActionTag": ""

feherke (Programmer) · Answer 6 · 2013-03-29 13:06:10

Hi

That is because putting a regular expression into a variable also includes the flags :

CODE --> perl -de 42

  DB<1> print qr{foo}
(?^:foo)
  DB<2> print qr{foo}i
(?^i:foo)

There the ?^ resets the flags locally inside the group. So you have to specify the case-insensitive flag at the qr :

CODE --> (fragment)

regular expression
my $pattern3 = qr{http://download\.microsoft\.com/download/.+?-$kb-$cpuTypeInL.*?.msu}i;
my $pattern4 = qr{http://download\.microsoft\.com/download/.+?-$kb-$cpuTypeInU.*?.msu}i;

Feherke.
http://feherke.github.com/

whn (Programmer) · Answer 7 · 2013-03-29 14:36:46

RE: Need help in construct an regexp

whn (Programmer)

(OP)

29 Mar 13 14:36

Excellent!! Thank you, Feherke.

Come Join Us!

Posting Guidelines

Need help in construct an regexp