1Text::BibTeX::Entry(3)User Contributed Perl DocumentationText::BibTeX::Entry(3)
2
6 Text::BibTeX::Entry - read and parse BibTeX files
7
9 use Text::BibTeX::Entry;
10 # ...assuming that $bibfile and $newbib are both objects of class
12 # Text::BibTeX::File, opened for reading and writing (respectively):
13 # Entry creation/parsing methods:
15 $entry = Text::BibTeX::Entry->new();
16 $entry->read ($bibfile);
17 $entry->parse ($filename, $filehandle);
18 $entry->parse_s ($entry_text);
19 # or:
21 $entry = Text::BibTeX::Entry->new( $bibfile );
22 $entry = Text::BibTeX::Entry->new( $filename, $filehandle );
23 $entry = Text::BibTeX::Entry->new( $entry_text );
24 # Entry query methods
26 warn "error in input" unless $entry->parse_ok;
27 $metatype = $entry->metatype;
28 $type = $entry->type;
29 # if metatype is BTE_REGULAR or BTE_MACRODEF:
31 $key = $entry->key; # only for BTE_REGULAR metatype
32 $num_fields = $entry->num_fields;
33 @fieldlist = $entry->fieldlist;
34 $has_title = $entry->exists ('title');
35 $title = $entry->get ('title');
36 # or:
37 ($val1,$val2,...$valn) = $entry->get ($field1, $field2, ..., $fieldn);
38 # if metatype is BTE_COMMENT or BTE_PREAMBLE:
40 $value = $entry->value;
41 # Author name methods
43 @authors = $entry->split ('author');
44 ($first_author) = $entry->names ('author');
45 # Entry modification methods
47 $entry->set_type ($new_type);
48 $entry->set_key ($new_key);
49 $entry->set ('title', $new_title);
50 # or:
51 $entry->set ($field1, $val1, $field2, $val2, ..., $fieldn, $valn);
52 $entry->delete (@fields);
53 $entry->set_fieldlist (\@fieldlist);
54 # Entry output methods
56 $entry->write ($newbib);
57 $entry->print ($filehandle);
58 $entry_text = $entry->print_s;
59 # Reset internal parser state:
61 $entry = Text::BibTeX::Entry->new();
62 $entry->parse ($filename, undef);
63 $entry->parse_s (undef);
64 # or:
66 $entry = Text::BibTeX::Entry->new( $filename, undef );
67 $entry = Text::BibTeX::Entry->new( undef );
68 # Miscellaneous methods
70 $entry->warn ($entry_warning);
71 # or:
72 $entry->warn ($field_warning, $field);
73 $entry->clone;
74
76 "Text::BibTeX::Entry" does all the real work of reading and parsing
77 BibTeX files. (Well, actually it just provides an object-oriented Perl
78 front-end to a C library that does all that. But that's not important
79 right now.)
80 BibTeX entries can be read either from "Text::BibTeX::File" objects
82 (using the "read" method), or directly from a filehandle (using the
83 "parse" method), or from a string (using "parse_s"). The first is
84 preferable, since you don't have to worry about supplying the filename,
85 and because of the extra functionality provided by the
86 "Text::BibTeX::File" class. Currently, this means that you may specify
87 the database structure to which entries are expected to conform via the
88 "File" class. This lets you ensure that entries follow the rules for
89 required fields and mutually constrained fields for a particular type
90 of database, and also gives you access to all the methods of the
91 structured entry class for this database structure. See
92 Text::BibTeX::Structure for details on database structures.
93 Once you have the entry, you can query it or change it in a variety of
95 ways. The query methods are "parse_ok", "type", "key", "num_fields",
96 "fieldlist", "exists", and "get". Methods for changing the entry are
97 "set_type", "set_key", "set_fieldlist", "delete", and "set".
98 Finally, you can output BibTeX entries, again either to an open
100 "Text::BibTeX::File" object, a filehandle or a string. (A filehandle
101 or "File" object must, of course, have been opened in write mode.)
102 Output to a "File" object is done with the "write" method, to a
103 filehandle via "print", and to a string with "print_s". Using the
104 "File" class is recommended for future extensibility, although it
105 currently doesn't offer anything extra.
106
108 Entry creation/parsing methods
109 new ([OPTS ,] [SOURCE])
110 Creates a new "Text::BibTeX::Entry" object. If the SOURCE
111 parameter is supplied, it must be one of the following: a
112 "Text::BibTeX::File" (or descendant class) object, a
113 filename/filehandle pair, or a string. Calls "read" to read from a
114 "Text::BibTeX::File" object, "parse" to read from a filehandle, and
115 "parse_s" to read from a string.
116 A filehandle can be specified as a GLOB reference, or as an
118 "IO::Handle" (or descendants) object, or as a "FileHandle" (or
119 descendants) object. (But there's really no point in using
120 "FileHandle" objects, since "Text::BibTeX" requires Perl 5.004,
121 which always includes the "IO" modules.) You can not pass in the
122 name of a filehandle as a string, though, because
123 "Text::BibTeX::Entry" conforms to the "use strict" pragma (which
124 disallows such symbolic references).
125 The corresponding filename should be supplied in order to allow for
127 accurate error messages; if you simply don't have the filename, you
128 can pass "undef" and you'll get error messages without a filename.
129 (It's probably better to rearrange your code so that the filename
130 is available, though.)
131 Thus, the following are equivalent to read from a file named by
133 $filename (error handling ignored):
134 # good ol' fashioned filehandle and GLOB ref
136 open (BIBFILE, $filename);
137 $entry = Text::BibTeX::Entry->new($filename, \*BIBFILE);
138 # newfangled IO::File thingy
140 $file = IO::File->new($filename);
141 $entry = Text::BibTeX::Entry->new($filename, $file);
142 But using a "Text::BibTeX::File" object is simpler and preferred:
144 $file = Text::BibTeX::File->new($filename);
146 $entry = Text::BibTeX::Entry->new($file);
147 Returns the new object, unless SOURCE is supplied and
149 reading/parsing the entry fails (e.g., due to end of file) -- then
150 it returns false.
151 You may supply a reference to an option hash as first argument.
153 Supported options are:
154 BINMODE
156 Set the way Text::BibTeX deals with strings. By default it
157 manages strings as bytes. You can set BINMODE to 'utf-8' to get
158 NFC normalized
159 Text::BibTeX::Entry->new(
161 { binmode => 'utf-8', normalization => 'NFD' },
162 $file });
163 NORMALIZATION
165 UTF-8 strings and you can customise the normalization with the
166 NORMALIZATION option.
167 clone
169 Clone a Text::BibTeX::Entry object, returning the clone. This re-
170 uses the reference to any Text::BibTeX::Structure or
171 Text::BibTeX::File but copies everything else, so that the clone
172 can be modified apart from the original.
173 read (BIBFILE)
175 Reads and parses an entry from BIBFILE, which must be a
176 "Text::BibTeX::File" object (or descendant). The next entry will
177 be read from the file associated with that object.
178 Returns the same as "parse" (or "parse_s"): false if no entry found
180 (e.g., at end-of-file), true otherwise. To see if the parse itself
181 failed (due to errors in the input), call the "parse_ok" method.
182 parse (FILENAME, FILEHANDLE)
184 Reads and parses the next entry from FILEHANDLE. (That is, it
185 scans the input until an '@' sign is seen, and then slurps up to
186 the next '@' sign. Everything between the two '@' signs [including
187 the first one, but not the second one -- it's pushed back onto the
188 input stream for the next entry] is parsed as a BibTeX entry, with
189 the simultaneous construction of an abstract syntax tree [AST].
190 The AST is traversed to ferret out the most interesting
191 information, and this is stuffed into a Perl hash, which
192 coincidentally is the "Text::BibTeX::Entry" object you've been
193 tossing around. But you don't need to know any of that -- I just
194 figured if you've read this far, you might want to know something
195 about the inner workings of this module.)
196 The success of the parse is stored internally so that you can later
198 query it with the "parse_ok" method. Even in the presence of
199 syntax errors, you'll usually get something resembling your input,
200 but it's usually not wise to try to do anything with it. Just call
201 "parse_ok", and if it returns false then silently skip to the next
202 entry. (The error messages printed out by the parser should be
203 quite adequate for the user to figure out what's wrong. And no,
204 there's currently no way for you to capture or redirect those error
205 messages -- they're always printed to "stderr" by the underlying C
206 code. That should change in future releases.)
207 If no '@' signs are seen on the input before reaching end-of-file,
209 then we've exhausted all the entries in the file, and "parse"
210 returns a false value. Otherwise, it returns a true value -- even
211 if there were syntax errors. Hence, it's important to check
212 "parse_ok".
213 The FILENAME parameter is only used for generating error messages,
215 but anybody using your program will certainly appreciate your
216 setting it correctly!
217 Passing "undef" to FILEHANDLE will reset the state of the
219 underlying C parser, which is required in order to parse multiple
220 files.
221 parse_s (TEXT)
223 Parses a BibTeX entry (using the above rules) from the string TEXT.
224 The string is not modified; repeatedly calling "parse_s" with the
225 same string will give you the same results each time. Thus,
226 there's no point in putting multiple entries in one string.
227 Passing "undef" to TEXT will reset the state of the underlying C
229 parser, which may be required in order to parse multiple strings.
230 Entry query methods
232 parse_ok ()
233 Returns false if there were any serious errors encountered while
234 parsing the entry. (A "serious" error is a lexical or syntax
235 error; currently, warnings such as "undefined macro" result in an
236 error message being printed to "stderr" for the user's edification,
237 but no notice is available to the calling code.)
238 type ()
240 Returns the type of the entry. (The `type' is the word that
241 follows the '@' sign; e.g. `article', `book', `inproceedings', etc.
242 for the standard BibTeX styles.)
243 metatype ()
245 Returns the metatype of the entry. (The `metatype' is a numeric
246 value used to classify entry types into four groups: comment,
247 preamble, macro definition (@string entries), and regular (all
248 other entry types). "Text::BibTeX" exports four constants for
249 these metatypes: "BTE_COMMENT", "BTE_PREAMBLE", "BTE_MACRODEF", and
250 "BTE_REGULAR".)
251 key ()
253 Returns the key of the entry. (The key is the token immediately
254 following the opening `{' or `(' in "regular" entries. Returns
255 "undef" for entries that don't have a key, such as macro definition
256 (@string) entries.)
257 num_fields ()
259 Returns the number of fields in the entry. (Note that, currently,
260 this is not equivalent to putting "scalar" in front of a call to
261 "fieldlist". See below for the consequences of calling "fieldlist"
262 in a scalar context.)
263 fieldlist ()
265 Returns the list of fields in the entry.
266 WARNING In scalar context, it no longer returns a reference to the
268 object's own list of fields.
269 exists (FIELD)
271 Returns true if a field named FIELD is present in the entry, false
272 otherwise.
273 get (FIELD, ...)
275 Returns the value of one or more FIELDs, as a list of values. For
276 example:
277 $author = $entry->get ('author');
279 ($author, $editor) = $entry->get ('author', 'editor');
280 If a FIELD is not present in the entry, "undef" will be returned at
282 its place in the return list. However, you can't completely trust
283 this as a test for presence or absence of a field; it is possible
284 for a field to be present but undefined. Currently this can only
285 happen due to certain syntax errors in the input, or if you pass an
286 undefined value to "set", or if you create a new field with
287 "set_fieldlist" (the new field's value is implicitly set to
288 "undef").
289 Normally, the field value is what the input looks like after
291 "maximal processing"--quote characters are removed, whitespace is
292 collapsed (the same way that BibTeX itself does it), macros are
293 expanded, and multiple tokens are pasted together. (See
294 bt_postprocess for details on the post-processing performed by
295 btparse.)
296 For example, if your input file has the following:
298 @string{of = "of"}
300 @string{foobars = "Foobars"}
301 @article{foobar,
303 title = { The Mating Habits } # of # " Adult " # foobars
304 }
305 then using "get" to query the value of the "title" field from the
307 "foobar" entry would give the string "The Mating Habits of Adult
308 Foobars".
309 However, in certain circumstances you may wish to preserve the
311 values as they appear in the input. This is done by setting a
312 "preserve_values" flag at some point; then, "get" will return not
313 strings but "Text::BibTeX::Value" objects. Each "Value" object is
314 a list of "Text::BibTeX::SimpleValue" objects, which in turn
315 consists of a simple value type (string, macro, or number) and the
316 text of the simple value. Various ways to set the
317 "preserve_values" flag and the interface to both "Value" and
318 "SimpleValue" objects are described in Text::BibTeX::Value.
319 value ()
321 Returns the single string associated with @comment and @preamble
322 entries. For instance, the entry
323 @preamble{" This is a preamble" #
325 {---the concatenation of several strings}}
326 would return a value of "This is a preamble---the concatenation of
328 several strings".
329 If this entry was parsed in "value preservation" mode, then "value"
331 acts like "get", and returns a "Value" object rather than a simple
332 string.
333 Author name methods
335 This is the only part of the module that makes any assumption about the
336 nature of the data, namely that certain fields are lists delimited by a
337 simple word such as "and", and that the delimited sub-strings are human
338 names of the "First von Last" or "von Last, Jr., First" style used by
339 BibTeX. If you are using this module for anything other than
340 bibliographic data, you can most likely forget about these two methods.
341 However, if you are in fact hacking on BibTeX-style bibliographic data,
342 these could come in very handy -- the name-parsing done by BibTeX is
343 not trivial, and the list-splitting would also be a pain to implement
344 in Perl because you have to pay attention to brace-depth. (Not that it
345 wasn't a pain to implement in C -- it's just a lot more efficient than
346 a Perl implementation would be.)
347 Incidentally, both of these methods assume that the strings being split
349 have already been "collapsed" in the BibTeX way, i.e. all leading and
350 trailing whitespace removed and internal whitespace reduced to single
351 spaces. This should always be the case when using these two methods on
352 a "Text::BibTeX::Entry" object, but these are actually just front ends
353 to more general functions in "Text::BibTeX". (More general in that you
354 supply the string to be parsed, rather than supplying the name of an
355 entry field.) Should you ever use those more general functions
356 directly, you might have to worry about collapsing whitespace; see
357 Text::BibTeX (the "split_list" and "split_name" functions in
358 particular) for more information.
359 Please note that the interface to author name parsing is experimental,
361 subject to change, and open to discussion. Please let me know if you
362 have problems with it, think it's just perfect, or whatever.
363 split (FIELD [, DELIM [, DESC]])
365 Splits the value of FIELD on DELIM (default: `and'). Don't assume
366 that this works the same as Perl's builtin "split" just because the
367 names are the same: in particular, DELIM must be a simple string
368 (no regexps), and delimiters that are at the beginning or end of
369 the string, or at non-zero brace depth, or not surrounded by
370 whitespace, are ignored. Some examples might illuminate matters:
371 if field F is... then split (F) returns...
373 'Name1 and Name2' ('Name1', 'Name2')
374 'Name1 and and Name2' ('Name1', undef, 'Name2')
375 'Name1 and' ('Name1 and')
376 'and Name2' ('and Name2')
377 'Name1 {and} Name2 and Name3' ('Name1 {and} Name2', 'Name3')
378 '{Name1 and Name2} and Name3' ('{Name1 and Name2}', 'Name3')
379 Note that a warning will be issued for empty names (as in the
381 second example above). A warning ought to be issued for delimiters
382 at the beginning or end of a string, but currently this isn't done.
383 (Hmmm.)
384 DESC is a one-word description of the substrings; it defaults to
386 'name'. It is only used for generating warning messages.
387 names (FIELD)
389 Splits FIELD as described above, and further splits each name into
390 four components: first, von, last, and jr.
391 Returns a list of "Text::BibTeX::Name" objects, each of which
393 represents one name. Use the "part" method to query these objects;
394 see Text::BibTeX::Name for details on the interface to name objects
395 (and on name-parsing as well).
396 For example if this entry:
398 @article{foo,
400 author = {John Smith and
401 Hacker, J. Random and
402 Ludwig van Beethoven and
403 {Foo, Bar and Company}}}
404 has been parsed into a "Text::BibTeX::Entry" object $entry, then
406 @names = $entry->names ('author');
408 will put a list of "Text::BibTeX::Name" objects in @names. These
410 can be queried individually as described in Text::BibTeX::Name; for
411 instance,
412 @last = $names[0]->part ('last');
414 would put the list of tokens comprising the last name of the first
416 author into the @last array: "('Smith')".
417 Entry modification methods
419 set_type (TYPE)
420 Sets the entry's type.
421 set_metatype (METATYPE)
423 Sets the entry's metatype (must be one of the four constants
424 "BTE_COMMENT", "BTE_PREAMBLE", "BTE_MACRODEF", and "BTE_REGULAR",
425 which are all optionally exported from "Text::BibTeX").
426 set_key (KEY)
428 Sets the entry's key.
429 set (FIELD, VALUE, ...)
431 Sets the value of field FIELD. (VALUE might be "undef" or
432 unsupplied, in which case FIELD will simply be set to "undef" --
433 this is where the difference between the "exists" method and
434 testing the definedness of field values becomes clear.)
435 Multiple (FIELD, VALUE) pairs may be supplied; they will be
437 processed in order (i.e. the input is treated like a list, not a
438 hash). For example:
439 $entry->set ('author', $author);
441 $entry->set ('author', $author, 'editor', $editor);
442 VALUE can be either a simple string or a "Text::BibTeX::Value"
444 object; it doesn't matter if the entry was parsed in "full post-
445 processing" or "preserve input values" mode.
446 delete (FIELD)
448 Deletes field FIELD from an entry.
449 set_fieldlist (FIELDLIST)
451 Sets the entry's list of fields to FIELDLIST, which must be a list
452 reference. If any of the field names supplied in FIELDLIST are not
453 currently present in the entry, they are created with the value
454 "undef" and a warning is printed. Conversely, if any of the fields
455 currently present in the entry are not named in the list of fields
456 supplied to "set_fields", they are deleted from the entry and
457 another warning is printed.
458 Entry output methods
460 write (BIBFILE)
461 Prints a BibTeX entry on the filehandle associated with BIBFILE
462 (which should be a "Text::BibTeX::File" object, opened for output).
463 Currently the printout is not particularly human-friendly; a highly
464 configurable pretty-printer will be developed eventually.
465 print (FILEHANDLE)
467 Prints a BibTeX entry on FILEHANDLE.
468 print_s ()
470 Prints a BibTeX entry to a string, which is the return value.
471 Miscellaneous methods
473 warn (WARNING [, FIELD])
474 Prepends a bit of location information (filename and line
475 number(s)) to WARNING, appends a newline, and passes it to Perl's
476 "warn". If FIELD is supplied, the line number given is just that
477 of the field; otherwise, the range of lines for the whole entry is
478 given. (Well, almost -- currently, the line number of the last
479 field is used as the last line of the whole entry. This is a bug.)
480 For example, if lines 10-15 of file foo.bib look like this:
482 @article{homer97,
484 author = {Homer Simpson and Ned Flanders},
485 title = {Territorial Imperatives in Modern Suburbia},
486 journal = {Journal of Suburban Studies},
487 year = 1997
488 }
489 then, after parsing this entry to $entry, the calls
491 $entry->warn ('what a silly entry');
493 $entry->warn ('what a silly journal', 'journal');
494 would result in the following warnings being issued:
496 foo.bib, lines 10-14: what a silly entry
498 foo.bib, line 13: what a silly journal
499 line ([FIELD])
501 Returns the line number of FIELD. If the entry was parsed from a
502 string, this still works--it's just the line number relative to the
503 start of the string. If the entry was parsed from a file, this
504 works just as you'd expect it to: it returns the absolute line
505 number with respect to the whole file. Line numbers are one-based.
506 If FIELD is not supplied, returns a two-element list containing the
508 line numbers of the beginning and end of the whole entry.
509 (Actually, the "end" line number is currently inaccurate: it's
510 really the the line number of the last field in the entry. But
511 it's better than nothing.)
512 filename ()
514 Returns the name of the file from which the entry was parsed. Only
515 works if the file is represented by a "Text::BibTeX::File"
516 object---if you just passed a filename/filehandle pair to "parse",
517 you can't get the filename back. (Sorry.)
518
520 Text::BibTeX, Text::BibTeX::File, Text::BibTeX::Structure
521
523 Greg Ward <gward@python.net>
524
526 Copyright (c) 1997-2000 by Gregory P. Ward. All rights reserved. This
527 file is part of the Text::BibTeX library. This library is free
528 software; you may redistribute it and/or modify it under the same terms
529 as Perl itself.
530perl v5.32.1 2021-01-27 Text::BibTeX::Entry(3)