NAME

MARC::Loop - process a batch of MARC21 records

SYNOPSIS

use MARC::Loop qw(marcloop marcbuild TAG VALREF DEL);
my $filehandle = \*STDIN;
my $deleted999 = 0;
my $fixed035 = 0;
marcloop {
    my ($leader, $fields, $raw_marc_ref) = @_;
    my $changed;
    foreach my $field (@$fields) {
        if ($field->[TAG] eq '035') {
            # Normalize OCLC numbers
            my $valref = $field->[VALREF];
            $$valref =~ s/\(OCoLC\)oc[mn]0*/(OCoLC)/g;
            $fixed035++;
            $changed = 1;
        }
        elsif ($field->[TAG] eq '999') {
            # Delete 999 fields
            $field->[DEL] = 1;
            $deleted999++;
            $changed = 1;
        }
    }
    # Print only changed records
    print marcbuild($leader, $fields) if $changed;
} $filehandle;
print STDERR "$deleted999 999 fields were deleted\n",
             "$fixed035 035 fields were fixed\n";

DESCRIPTION

MARC::Loop is an alternative to MARC::File and MARC::Record that eschews an object-oriented approach in favor of a bare-bones procedural one.

FUNCTIONS

All of these functions are exported upon request.

marcloop

# This example prints a MARC record in human-readable form, using a single
# line for each field no matter how many subfields it might have.
use MARC::Loop qw(marcloop);
marcloop {
    my ($leader, $fields, $raw_marc_ref) = @_;
    foreach my $field (@$fields) {
        if ($field->[TAG] lt '010) {
            # Control field
            my $valref = $field->[VALREF];
            print $field->[TAG], '    ', $$valref, "\n";
        }
        else {
            # Data field 
            my ($i1, $i2) = ($field->[IND1], $field->[IND2]);
            print "$field->[TAG] $i1$i2";
            my @subfields  = @{ $field->[SUBS..$#$field] };
            foreach my $subfield (@subfields) {
                my ($code, $valref) = @$subfield;
                print '$', $code, ' ', $$valref;
            }
            print "\n";
        }
    }
} $filehandle, %options;

Options:

print_all

All MARC records will be printed to STDOUT. Any changes you make will be reflected in what is printed.

drop array_ref

'drop' => [ '001', '090' ]

Tags of fields to be dropped unconditionally.

only array_ref

'only' => [ qw(001 004 008 852 856) ]

Tags of fields to be preserved; all other fields will be dropped. (The leader is never dropped, of course.)

error

A code reference to call when there is an error.

'error' => sub { exit -1 }

strict

'strict' => 1

Halt processing when an ill-formed MARC record is encountered.

Options will be more fully documented in a future release; in the meantime, read the source code.

marcparse

($leader, $fields) = marcparse(\$string, %options);

Parses a MARC record into the same data structure that marcloop uses. Options are mostly the same as for marcloop.

marcbuild

print marcbuild($leader, $fields);

Builds a raw MARC record from the same data structure that marcloop uses and that marcparse produces.

marcfield

# Control field
push $@fields, marcfield(                  
    '001',   # Tag
    1234567, # Content
);  

# Data field
push $@fields, marcfield(                  
    '245',              # Tag
    ' ', ' ',           # Indicators
    'a' => 'Blah blah', # Subfield $a
    'c' => 'Amy Emu',   # Subfield $c
    ...                 # More subfields
);

A convenience function to build a data structure representing a single MARC21 field.

BUGS

The documentation is woefully lacking and probably just plain wrong. Read the source code -- or, better yet, step through it in the Perl debugger -- to get a better understanding of what this code does.

Unhandled errors cause ill-formed records to be dropped without notice. You must specify an error option to marcloop to get around this.

AUTHOR

Paul Hoffman <paul@flo.org>.

COPYRIGHT

Copyright 2009-2010 Fenway Libraries Online. Released under the GNU Public License, version 3.