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Learning Perl on Win32 Systems

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Previous: A.15 Chapter 16, System InformationAppendix A
Exercise Answers
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A.16 Chapter 17, Database Manipulation

  1. Here's one way to do it:

    # program 1:
    dbmopen(%WORDS,"words",0644);
    while (<>) {
      foreach $word (split(/\W+/)) {
        $WORDS{$word}++;
      }
    }
    dbmclose(%WORDS);

    The first program (the writer) opens a DBM in the current directory called words, creating files named words.dir and words.pag. The while loop grabs each line using the diamond operator. This line is split apart using the split operator, with a delimiter of /\W+/, meaning nonword characters. Each word is then counted into the DBM array, using the foreach statement to step through the words.

    # program 2:
    dbmopen(%WORDS,"words",undef);
    foreach $word (sort { $WORDS{$b} <=> $WORDS{$a} } keys %WORDS) {
      print "$word $WORDS{$word}\n";
    }
    dbmclose(%WORDS);

    The second program opens a DBM in the current directory called words. That complicated looking foreach line does most of the dirty work. The value of $word each time through the loop will be the next element of a list. The list is the sorted keys from %WORDS, sorted by their values (the count) in descending order. For each word in the list, we print the word and the number of times the word has occurred.


Previous: A.15 Chapter 16, System InformationLearning Perl on Win32 SystemsNext: A.17 Chapter 18, CGI Programming
A.15 Chapter 16, System InformationBook IndexA.17 Chapter 18, CGI Programming