NAME

SYNOPSIS

   #!/bin/perl
   # Read a series of People records from STDIN.
   # Add an "Eligible" tag to all those whose
   # Age >= 35 and Friends list includes "Fred"
   use Boulder::Stream;
   
   # filestream way:
   my $stream = Boulder::Stream->newFh;
   while ( my $record = <$stream> ) {
      next unless $record->Age >= 35;
      my @friends = $record->Friends;
      next unless grep {$_ eq 'Fred'} @friends;

      $record->insert(Eligible => 'yes');
      print $stream $record;
    }

    # object oriented way:
   my $stream = Boulder::Stream->new;
   while (my $record = $stream->get ) {
      next unless $record->Age >= 35;
      my @friends = $record->Friends;
      next unless grep {$_ eq 'Fred'} @friends;

      $record->insert(Eligible => 'yes');
      print $stream $record;
    }

DESCRIPTION

By default, data is read from the magic ARGV filehandle (STDIN or a list of files provided on the command line) and written to STDOUT. This can be changed to the filehandles of your choice.

  query_database | find_vector | find_dups | \
    | blast_sequence | pick_primer | mail_report

SKELETON BOULDER PROGRAM

   #!/bin/perl
   use Boulder::Stream;
   
   my $stream = Boulder::Stream->newFh;
   
   while ( my $record = <$stream> ) {
      next unless $record->Age >= 35;
      my @friends = $record->Friends;
      next unless grep {$_ eq 'Fred'} @friends;

      $record->insert(Eligible => 'yes');
      print $stream $record;
    }

The code starts by creating a Boulder::Stream object to handle the I/O. It reads from the stream one record at a time, returning a Stone object. We recover the Age and Friends tags, and continue looping unless the Age is greater or equal to 35, and the list of Friends contains "Fred". If these criteria match, then we insert a new tag named Eligible and print the record to the stream. The output may look like this:

  Name=Janice
  Age=36
  Eligible=yes
  Friends=Susan
  Friends=Fred
  Friends=Ralph
  =
  Name=Ralph
  Age=42
  Eligible=yes
  Friends=Janice
  Friends=Fred
  =
  Name=Susan
  Age=35
  Eligible=yes
  Friends=Susan
  Friends=Fred
  =

Note that in this case only records that meet the criteria are echoed to standard output. The object-oriented version of the program looks like this:

   #!/bin/perl
   use Boulder::Stream;
   
   my $stream = Boulder::Stream->new;
   
   while ( my $record = $stream->get('Age','Friends') ) {
      next unless $record->Age >= 35;
      my @friends = $record->Friends;
      next unless grep {$_ eq 'Fred'} @friends;

      $record->insert(Eligible => 'yes');
      $stream->put($record);
    }

The get() method is used to fetch Stones containing one or more of the indicated tags. The put() method is used to send the result to standard output. The pass-through behavior might produce a set of records like this one:

  Name=Janice
  Age=36
  Eligible=yes
  Friends=Susan
  Friends=Fred
  Friends=Ralph
  =
  Name=Phillip
  Age=30
  =
  Name=Ralph
  Age=42
  Eligible=yes
  Friends=Janice
  Friends=Fred
  =
  Name=Barbara
  Friends=Agatha
  Friends=Janice
  =
  Name=Susan
  Age=35
  Eligible=yes
  Friends=Susan
  Friends=Fred
  =

Notice that there are now two records ("Phillip" and "Barbara") that do not contain the Eligible tag.

Boulder::Stream METHODS

  $stream = tied $fh;

        $a = new Boulder::Stream;
        $a->{delim}=':';
        $a->{record_start}='[';
        $a->{record_end}=']';
        $a->{passthru}=undef;

BUGS

AUTHOR

SEE ALSO