1MARC::Field(3) User Contributed Perl Documentation MARC::Field(3)
2
6 MARC::Field - Perl extension for handling MARC fields
7
9 use MARC::Field;
10 # If your system uses wacky control field tags, add them
12 MARC::Field->allow_controlfield_tags('FMT', 'LLE');
13 my $field = MARC::Field->new( 245, '1', '0',
15 'a' => 'Raccoons and ripe corn / ',
16 'c' => 'Jim Arnosky.'
17 );
18 $field->add_subfields( "a", "1st ed." );
19
21 Defines MARC fields for use in the MARC::Record module. I suppose you
22 could use them on their own, but that wouldn't be very interesting.
23
25 None by default. Any errors are stored in $MARC::Field::ERROR, which
26 $MARC::Record usually bubbles up to $MARC::Record::ERROR.
27
29 extra_controlfield_tags: Some systems (notably Ex Libris's Aleph) throw
30 extra control fields in their MARC (e.g., Aleph's MARC-XML tends to
31 have a "FMT" control field). We keep a class-level hash to track to
32 track them; it can be manipulated with "allow_controlfield_tags" and
33 c<disallow_controlfield_tags>.
34
36 new()
37 The constructor, which will return a MARC::Field object. Typically you
38 will pass in the tag number, indicator 1, indicator 2, and then a list
39 of any subfield/data pairs. For example:
40 my $field = MARC::Field->new(
42 245, '1', '0',
43 'a' => 'Raccoons and ripe corn / ',
44 'c' => 'Jim Arnosky.'
45 );
46 Or if you want to add a control field (< 010) that does not have
48 indicators.
49 my $field = MARC::Field->new( '001', ' 14919759' );
51 tag()
53 Returns the three digit tag for the field.
54 set_tag(tag)
56 Changes the tag number of this field. Updates the control status
57 accordingly. Will "croak" if an invalid value is passed in.
58 indicator(indno)
60 Returns the specified indicator. Returns "undef" and logs a warning if
61 field is a control field and thus doesn't have indicators. If the
62 field is not a control field, croaks if the indno is not 1 or 2.
63 set_indicator($indno, $indval)
65 Set the indicator position $indno to the value specified by $indval.
66 Croaks if the indicator position, is invalid, the field is a control
67 field and thus doesn't have indicators, or if the new indicator value
68 is invalid.
69 allow_controlfield_tags($tag, $tag2, ...)
71 Add $tags to class-level list of strings to consider valid control
72 fields tags (in addition to 001 through 009). Tags must have three
73 characters.
74 disallow_controlfield_tags($tag, $tag2, ...) =head2
76 disallow_controlfield_tags('*')
77 Revoke the validity of a control field tag previously added with
78 allow_controlfield_tags. As a special case, if you pass the string '*'
79 it will clear out all previously-added tags.
80 NOTE that this will only deal with stuff added with
82 allow_controlfield_tags; you can't disallow '001'.
83 is_valid_tag($tag) -- is the given tag valid?
85 Generally called as a class method (e.g.,
86 MARC::Field->is_valid_tag('001'))
87 is_valid_indicator($indval) -- is the given indicator value valid?
89 Generally called as a class method (e.g.,
90 MARC::Field->is_valid_indicator('4'))
91 is_controlfield_tag($tag) -- does the given tag denote a control field?
93 Generally called as a class method (e.g.,
94 MARC::Field->is_controlfield_tag('001'))
95 is_control_field()
97 Tells whether this field is one of the control tags from 001-009.
98 subfield(code)
100 When called in a scalar context returns the text from the first
101 subfield matching the subfield code.
102 my $subfield = $field->subfield( 'a' );
104 Or if you think there might be more than one you can get all of them by
106 calling in a list context:
107 my @subfields = $field->subfield( 'a' );
109 If no matching subfields are found, "undef" is returned in a scalar
111 context and an empty list in a list context.
112 If the tag is a control field, "undef" is returned and
114 $MARC::Field::ERROR is set.
115 subfields()
117 Returns all the subfields in the field. What's returned is a list of
118 list refs, where the inner list is a subfield code and the subfield
119 data.
120 For example, this might be the subfields from a 245 field:
122 (
124 [ 'a', 'Perl in a nutshell :' ],
125 [ 'b', 'A desktop quick reference.' ],
126 )
127 data()
129 Returns the data part of the field, if the tag number is less than 10.
130 add_subfields(code,text[,code,text ...])
132 Adds subfields to the end of the subfield list.
133 $field->add_subfields( 'c' => '1985' );
135 Returns the number of subfields added, or "undef" if there was an
137 error.
138 delete_subfield()
140 delete_subfield() allows you to remove subfields from a field:
141 # delete any subfield a in the field
143 $field->delete_subfield(code => 'a');
144 # delete any subfield a or u in the field
146 $field->delete_subfield(code => ['a', 'u']);
147 # delete any subfield code matching a compiled regular expression
149 $field->delete_subfield(code => qr/[^a-z0-9]/);
150 If you want to only delete subfields at a particular position you can
152 use the pos parameter:
153 # delete subfield u at the first position
155 $field->delete_subfield(code => 'u', pos => 0);
156 # delete subfield u at first or second position
158 $field->delete_subfield(code => 'u', pos => [0,1]);
159 # delete the second subfield, no matter what it is
161 $field->delete_subfield(pos => 1);
162 You can specify a regex to for only deleting subfields that match:
164 # delete any subfield u that matches zombo.com
166 $field->delete_subfield(code => 'u', match => qr/zombo.com/);
167 # delete any subfield that matches quux
169 $field->delete_subfield(match => qr/quux/);
170 You can also pass a single subfield label:
172 # delete all subfield u
174 $field->delete_subfield('u');
175 delete_subfields()
177 Delete all subfields with a given subfield code. This is here for
178 backwards compatibility, you should use the more flexible
179 delete_subfield().
180 update()
182 Allows you to change the values of the field. You can update indicators
183 and subfields like this:
184 $field->update( ind2 => '4', a => 'The ballad of Abe Lincoln');
186 If you attempt to update a subfield which does not currently exist in
188 the field, then a new subfield will be appended to the field. If you
189 don't like this auto-vivification you must check for the existence of
190 the subfield prior to update.
191 if ( $field->subfield( 'a' ) ) {
193 $field->update( 'a' => 'Cryptonomicon' );
194 }
195 If you want to update a field that has no indicators or subfields
197 (000-009) just call update() with one argument, the string that you
198 would like to set the field to.
199 $field = $record->field( '003' );
201 $field->update('IMchF');
202 Note: when doing subfield updates be aware that "update()" will only
204 update the first occurrence. If you need to do anything more
205 complicated you will probably need to create a new field and use
206 "replace_with()".
207 Returns the number of items modified.
209 replace_with()
211 Allows you to replace an existing field with a new one. You need to
212 pass "replace()" a MARC::Field object to replace the existing field
213 with. For example:
214 $field = $record->field('245');
216 my $new_field = new MARC::Field('245','0','4','The ballad of Abe Lincoln.');
217 $field->replace_with($new_field);
218 Doesn't return a meaningful or reliable value.
220 as_string( [$subfields] [, $delimiter] )
222 Returns a string of all subfields run together. A space is added to the
223 result between each subfield, unless the delimiter parameter is passed.
224 The tag number and subfield character are not included.
225 Subfields appear in the output string in the order in which they occur
227 in the field.
228 If $subfields is specified, then only those subfields will be included.
230 my $field = MARC::Field->new(
232 245, '1', '0',
233 'a' => 'Abraham Lincoln',
234 'h' => '[videorecording] :',
235 'b' => 'preserving the union /',
236 'c' => 'A&E Home Video.'
237 );
238 print $field->as_string( 'abh' ); # Only those three subfields
239 # prints 'Abraham Lincoln [videorecording] : preserving the union /'.
240 print $field->as_string( 'ab', '--' ); # Only those two subfields, with a delimiter
241 # prints 'Abraham Lincoln--preserving the union /'.
242 Note that subfield h comes before subfield b in the output.
244 as_formatted()
246 Returns a pretty string for printing in a MARC dump.
247 as_usmarc()
249 Returns a string for putting into a USMARC file. It's really only
250 useful for "MARC::Record::as_usmarc()".
251 clone()
253 Makes a copy of the field. Note that this is not just the same as
254 saying
255 my $newfield = $field;
257 since that just makes a copy of the reference. To get a new object,
259 you must
260 my $newfield = $field->clone;
262 Returns a MARC::Field record.
264 warnings()
266 Returns the warnings that were created when the record was read. These
267 are things like "Invalid indicators converted to blanks".
268 The warnings are items that you might be interested in, or might not.
270 It depends on how stringently you're checking data. If you're doing
271 some grunt data analysis, you probably don't care.
272
274 See the "SEE ALSO" section for MARC::Record.
275
277 See the "TODO" section for MARC::Record.
278
280 This code may be distributed under the same terms as Perl itself.
281 Please note that these modules are not products of or supported by the
283 employers of the various contributors to the code.
284
286 Andy Lester, "<andy@petdance.com>"
287perl v5.36.0 2022-07-22 MARC::Field(3)