1XBase(3) User Contributed Perl Documentation XBase(3)
2
6 XBase - Perl module for reading and writing the dbf files
7
9 use XBase;
10 my $table = new XBase "dbase.dbf" or die XBase->errstr;
11 for (0 .. $table->last_record) {
12 my ($deleted, $id, $msg)
13 = $table->get_record($_, "ID", "MSG");
14 print "$id:\t$msg\n" unless $deleted;
15 }
16
18 This module can read and write XBase database files, known as dbf in
19 dBase and FoxPro world. It also reads memo fields from the dbt and fpt
20 files, if needed. An alpha code of reading index support for ndx, ntx,
21 mdx, idx and cdx is available for testing -- see the DBD::Index(3) man
22 page. Module XBase provides simple native interface to XBase files.
23 For DBI compliant database access, see the DBD::XBase and DBI modules
24 and their man pages.
25 The following methods are supported by XBase module:
27 General methods
29 new Creates the XBase object, loads the info about the table form the
30 dbf file. The first parameter should be the name of existing dbf
31 file (table, in fact) to read. A suffix .dbf will be appended if
32 needed. This method creates and initializes new object, will also
33 check for memo file, if needed.
34 The parameters can also be specified in the form of hash: value of
36 name is then the name of the table, other flags supported are:
37 memofile specifies non standard name for the associated memo file.
39 By default it's the name of the dbf file, with extension dbt or
40 fpt.
41 ignorememo ignore memo file at all. This is usefull if you've lost
43 the dbt file and you do not need it. Default is false.
44 memosep separator of memo records in the dBase III dbt files. The
46 standard says it should be "\x1a\x1a". There are however
47 implamentations that only put in one "\x1a". XBase.pm tries to
48 guess which is valid for your dbt but if it fails, you can tell it
49 yourself.
50 nolongchars prevents XBase to treat the decimal value of character
52 fields as high byte of the length -- there are some broken products
53 around producing character fields with decimal values set.
54 my $table = new XBase "table.dbf" or die XBase->errstr;
56 my $table = new XBase "name" => "table.dbf",
58 "ignorememo" => 1;
59 recompute_lastrecno forces XBase.pm to disbelieve the information
61 about the number of records in the header of the dbf file and
62 recompute the number of records. Use this only if you know that
63 some other software of yours produces incorrect headers.
64 close
66 Closes the object/file, no arguments.
67 create
69 Creates new database file on disk and initializes it with 0
70 records. A dbt (memo) file will be also created if the table
71 contains some memo fields. Parameters to create are passed as hash.
72 You can call this method as method of another XBase object and then
74 you only need to pass name value of the hash; the structure
75 (fields) of the new file will be the same as of the original
76 object.
77 If you call create using class name (XBase), you have to (besides
79 name) also specify another four values, each being a reference to
80 list: field_names, field_types, field_lengths and field_decimals.
81 The field types are specified by one letter strings (C, N, L, D,
82 ...). If you set some value as undefined, create will make it into
83 some reasonable default.
84 my $newtable = $table->create("name" => "copy.dbf");
86 my $newtable = XBase->create("name" => "copy.dbf",
88 "field_names" => [ "ID", "MSG" ],
89 "field_types" => [ "N", "C" ],
90 "field_lengths" => [ 6, 40 ],
91 "field_decimals" => [ 0, undef ]);
92 Other attributes are memofile for non standard memo file location,
94 codepage to set the codepage flag in the dbf header (it does not
95 affect how XBase.pm reads or writes the data though, just to make
96 FoxPro happy), and version to force different version of the dbt
97 (dbt) file. The default is the version of the object from which you
98 create the new one, or 3 if you call this as class method
99 (XBase->create).
100 The new file mustn't exist yet -- XBase will not allow you to
102 overwrite existing table. Use drop (or unlink) to delete it first.
103 drop
105 This method closes the table and deletes it on disk (including
106 associated memo file, if there is any).
107 last_record
109 Returns number of the last record in the file. The lines deleted
110 but present in the file are included in this number.
111 last_field
113 Returns number of the last field in the file, number of fields
114 minus 1.
115 field_names, field_types, field_lengths, field_decimals
117 Return list of field names and so on for the dbf file.
118 field_type, field_length, field_decimal
120 For a field name, returns the appropriate value. Returns undef if
121 the field doesn't exist in the table.
122 Reading the data one by one
124 When dealing with the records one by one, reading or writing (the
125 following six methods), you have to specify the number of the record in
126 the file as the first argument. The range is "0 ..
127 $table->last_record".
128 get_record
130 Returns a list of data (field values) from the specified record
131 (line of the table). The first parameter in the call is the number
132 of the record. If you do not specify any other parameters, all
133 fields are returned in the same order as they appear in the file.
134 You can also put list of field names after the record number and
135 then only those will be returned. The first value of the returned
136 list is always the 1/0 "_DELETED" value saying whether the record
137 is deleted or not, so on success, get_record never returns empty
138 list.
139 get_record_nf
141 Instead if the names of the fields, you can pass list of numbers of
142 the fields to read.
143 get_record_as_hash
145 Returns hash (in list context) or reference to hash (in scalar
146 context) containing field values indexed by field names. The name
147 of the deleted flag is "_DELETED". The only parameter in the call
148 is the record number. The field names are returned as uppercase.
149 Writing the data
151 All three writing methods always undelete the record. On success they
152 return true -- the record number actually written.
153 set_record
155 As parameters, takes the number of the record and the list of
156 values of the fields. It writes the record to the file. Unspecified
157 fields (if you pass less than you should) are set to undef/empty.
158 set_record_hash
160 Takes number of the record and hash as parameters, sets the fields,
161 unspecified are undefed/emptied.
162 update_record_hash
164 Like set_record_hash but fields that do not have value specified in
165 the hash retain their value.
166 To explicitely delete/undelete a record, use methods delete_record or
168 undelete_record with record number as a parameter.
169 Assorted examples of reading and writing:
171 my @data = $table->get_record(3, "jezek", "krtek");
173 my $hashref = $table->get_record_as_hash(38);
174 $table->set_record_hash(8, "jezek" => "jezecek",
175 "krtek" => 5);
176 $table->undelete_record(4);
177 This is a code to update field MSG in record where ID is 123.
179 use XBase;
181 my $table = new XBase "test.dbf" or die XBase->errstr;
182 for (0 .. $table->last_record) {
183 my ($deleted, $id) = $table->get_record($_, "ID")
184 die $table->errstr unless defined $deleted;
185 next if $deleted;
186 $table->update_record_hash($_, "MSG" => "New message")
187 if $id == 123;
188 }
189 Sequentially reading the file
191 If you plan to sequentially walk through the file, you can create a
192 cursor first and then repeatedly call fetch to get next record.
193 prepare_select
195 As parameters, pass list of field names to return, if no
196 parameters, the following fetch will return all fields.
197 prepare_select_with_index
199 The first parameter is the file name of the index file, the rest is
200 as above. For index types that can hold more index structures in on
201 file, use arrayref instead of the file name and in that array
202 include file name and the tag name, and optionaly the index type.
203 The fetch will then return records in the ascending order,
204 according to the index.
205 Prepare will return object cursor, the following method are methods of
207 the cursor, not of the table.
208 fetch
210 Returns the fields of the next available undeleted record. The list
211 thus doesn't contain the "_DELETED" flag since you are guaranteed
212 that the record is not deleted.
213 fetch_hashref
215 Returns a hash reference of fields for the next non deleted record.
216 last_fetched
218 Returns the number of the record last fetched.
219 find_eq
221 This only works with cursor created via prepare_select_with_index.
222 Will roll to the first record what is equal to specified argument,
223 or to the first greater if there is none equal. The following
224 fetches then continue normally.
225 Examples of using cursors:
227 my $table = new XBase "names.dbf" or die XBase->errstr;
229 my $cursor = $table->prepare_select("ID", "NAME", "STREET");
230 while (my @data = $cursor->fetch) {
231 ### do something here, like print "@data\n";
232 }
233 my $table = new XBase "employ.dbf";
235 my $cur = $table->prepare_select_with_index("empid.ndx");
236 ## my $cur = $table->prepare_select_with_index(
237 ["empid.cdx", "ADDRES", "char"], "id", "address");
238 $cur->find_eq(1097);
239 while (my $hashref = $cur->fetch_hashref
240 and $hashref->{"ID"} == 1097) {
241 ### do something here with $hashref
242 }
243 The second example shows that after you have done find_eq, the fetches
245 continue untill the end of the index, so you have to check whether you
246 are still on records with given value. And if there is no record with
247 value 1097 in the indexed field, you will just get the next record in
248 the order.
249 The updating example can be rewritten to:
251 use XBase;
253 my $table = new XBase "test.dbf" or die XBase->errstr;
254 my $cursor = $table->prepare_select("ID")
255 while (my ($id) = $cursor->fetch) {
256 $table->update_record_hash($cursor->last_fetched,
257 "MSG" => "New message") if $id == 123
258 }
259 Dumping the content of the file
261 A method get_all_records returns reference to an array containing array
262 of values for each undeleted record at once. As parameters, pass list
263 of fields to return for each record.
264 To print the content of the file in a readable form, use method
266 dump_records. It prints all not deleted records from the file. By
267 default, all fields are printed, separated by colons, one record on a
268 row. The method can have parameters in a form of a hash with the
269 following keys:
270 rs Record separator, string, newline by default.
272 fs Field separator, string, one colon by default.
274 fields
276 Reference to a list of names of the fields to print. By default
277 it's undef, meaning all fields.
278 undef
280 What to print for undefined (NULL) values, empty string by default.
281 Example of use is
283 use XBase;
285 my $table = new XBase "table" or die XBase->errstr;
286 $table->dump_records("fs" => " | ", "rs" => " <-+\n",
287 "fields" => [ "id", "msg" ]);'
288 Also note that there is a script dbfdump.pl(1) that does the printing.
290 Errors and debugging
292 If the method fails (returns false or null list), the error message can
293 be retrieved via errstr method. If the new or create method fails, you
294 have no object so you get the error message using class syntax
295 "XBase->errstr()".
296 The method header_info returns (not prints) string with information
298 about the file and about the fields.
299 Module XBase::Base(3) defines some basic functions that are inherited
301 by both XBase and XBase::Memo(3) module.
302
304 The character fields are returned "as is". No charset or other
305 translation is done. The numbers are converted to Perl numbers. The
306 date fields are returned as 8 character string of the 'YYYYMMDD' form
307 and when inserting the date, you again have to provide it in this form.
308 No checking for the validity of the date is done. The datetime field is
309 returned in the number of (possibly negative) seconds since 1970/1/1,
310 possibly with decimal part (since it allows precision up to 1/1000 s).
311 To get the fields, use the gmtime (or similar) Perl function.
312 If there is a memo field in the dbf file, the module tries to open file
314 with the same name but extension dbt, fpt or smt. It uses module
315 XBase::Memo(3) for this. It reads and writes this memo field
316 transparently (you do not know about it) and returns the data as single
317 scalar.
318
320 New: A support for ndx, ntx, mdx, idx and cdx index formats is
321 available with alpha status for testing. Some of the formats are
322 already rather stable (ndx). Please read the XBase::Index(3) man page
323 and the eg/use_index file in the distribution for examples and ideas.
324 Send me examples of your data files and suggestions for interface if
325 you need indexes.
326 General locking methods are locksh, lockex and unlock for shared lock,
328 exclusive lock and unlock. They call flock but you can redefine then in
329 XBase::Base package.
330
332 This module is built using information from and article XBase File
333 Format Description by Erik Bachmann, URL
334 http://www.clicketyclick.dk/databases/xbase/format/
336 Thanks a lot.
338
340 1.08
341
343 http://www.adelton.com/perl/DBD-XBase/
344
346 (c) 1997--2017 Jan Pazdziora.
347 All rights reserved. This package is free software; you can
349 redistribute it and/or modify it under the same terms as Perl itself.
350 Contact the author at jpx dash perl at adelton dot com.
352
354 Many people have provided information, test files, test results and
355 patches. This project would not be so great without them. See the
356 Changes file for (I hope) complete list. Thank you all, guys!
357 Special thanks go to Erik Bachmann for his great page about the file
359 structures; to Frans van Loon, William McKee, Randy Kobes and Dan
360 Albertsson for longtime cooperation and many emails we've exchanged
361 when fixing and polishing the modules' behaviour; and to Dan Albertsson
362 for providing support for the project.
363
365 perl(1); XBase::FAQ(3); DBD::XBase(3) and DBI(3) for DBI interface;
366 dbfdump.pl(1)
367perl v5.34.0 2022-01-21 XBase(3)