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

<lt=c24>PRL IJB PRL CHA <refauth><fname>K.</fname> <middlename>M.</mid
+dlename> <surname>Cuomo</surname></refauth> and <refauth><fname>A.</f
+name> <middlename>V.</middlename> <surname>Oppenheim</surname></refau
+th>, <jtitle>Phys. Rev. Lett.</jtitle> <B><volume>71</volume>,</B> <p
+ages>65</pages> (<date>1993</date>); <refauth><fname>L.</fname> <surn
+ame>Kocarev</surname></refauth>, <refauth><fname>K.</fname> <middlena
+me>S.</middlename> <surname>Halle</surname></refauth>, <refauth><fnam
+e>K.</fname> <surname>Eckert</surname></refauth>, <refauth><fname>L.<
+/fname> <middlename>O.</middlename> <surname>Chua</surname></refauth>
+, and <refauth><fname>U.</fname> <surname>Parlitz</surname></refauth>
+, <jtitle>Int. J. Bifurcation Chaos Appl. Sci. Eng.</jtitle> <B><volu
+me>2</volume>,</B> <pages>973</pages> (<date>1992</date>); <refauth><
+fname>L.</fname> <surname>Kocarev</surname></refauth> and <refauth><f
+name>U.</fname> <surname>Parlitz</surname></refauth>, <jtitle>Phys. R
+ev. Lett.</jtitle> <B><volume>74</volume>,</B> <pages>5028</pages> (<
+date>1995</date>); <refauth><fname>N.</fname> <middlename>F.</middlen
+ame> <surname>Rulkov</surname></refauth>, <jtitle>Chaos</jtitle> <B><
+volume>6</volume>,</B> <pages>262</pages> (<date>1996</date>).</lt>

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How to backtrack the below pairs of information from the above line. the number of pairs/line may chage from a range of 0 to 5 
PRL  <jtitle>Phys. Rev. Lett.</jtitle>
IJB  <jtitle>Int. J. Bifurcation Chaos Appl. Sci. Eng.</jtitle>
PRL  <jtitle>Phys. Rev. Lett.</jtitle>
CHB  <jtitle>Chaos</jtitle>

[download]
Regards,
Ganesh

20050624 Edit by ysth: code, br tags

Replies are listed 'Best First'.
Re: Backtracking
by tlm (Prior) on Jun 24, 2005 at 11:31 UTC

    I will guess that by "backtrack" what you mean is "extract". If so, then look into XML::Parser or XML::Twig.

    the lowliest monk

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Re: Backtracking
by fmerges (Chaplain) on Jun 24, 2005 at 10:14 UTC
    Hi
    I don't really understood the problem, but I you want to get out this tags you could use a loop to get over the lines, or parse using a Parser suitable, and store the values into a hash, you could use something like: 
    $hash = {
      jtitle => ['a', 'b'],
      ...
}

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    Regards,
    :)
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[d/l]
Re: Backtracking
by Animator (Hermit) on Jun 24, 2005 at 14:42 UTC

    Here is another way (which works by removing the text it extracted):

    $out = "";
while ($data =~ s#(<lt=c24>)(\w{3} ?)(.*?)(<jtitle>.*?</jtitle>)#$1$3#
+is) { 
  $out .= $2. " " . $4 . "\n"; 
}

    [download]

    Written as a one-liner this gives: 

    perl -p0 -e '$x="";while (s#(<lt=c24>)(\w{3} ?)(.*?)(<jtitle>.*?</jtit
+le>)#$1$3#is) { $x.=$2." ".$4."\n"; } } $_ = $x; {' data

    [download]

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Re: Backtracking
by sapnac (Beadle) on Jun 24, 2005 at 14:33 UTC
    I bet many there are many other better ways; 
    
Here is a quick way;

#  Global declarations

open(spooler,"test.html") or die "Can't open file\n";
while($spool=<spooler>){
    $spool;
    @value=split(/<*>*</,$spool);
    $i=0;$j=0;
    while ($i<= $#value) {
        if ($value[$i] =~  /lt=c24/i ) {
            $value[$i] =~  s/lt=c24>//g;
            @val1=split(/ /,$value[$i]);
           }
        if($value[$i] =~ /^jtitle>/i) {
           #$value[$i]    =~  s/^jtitle>//ig;
           $val2[$j]=$value[$i];
           $j++;
           }
        $i++;
   }
}

for($n=0;$n<$j; $n++)
{
    print $val1[$n]."  <".$val2[$n]."<jtitle>\n";
}

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    Hope it helps!
[reply]
[d/l]

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