XBase(3) User Contributed Perl Documentation XBase(3)NAMEXBase - Perl module for reading and writing the dbf files
SYNOPSIS
use XBase;
my $table = new XBase "dbase.dbf" or die XBase->errstr;
for (0 .. $table->last_record) {
my ($deleted, $id, $msg)
= $table->get_record($_, "ID", "MSG");
print "$id:\t$msg\n" unless $deleted;
}
DESCRIPTION
This module can read and write XBase database files, known as dbf in
dBase and FoxPro world. It also reads memo fields from the dbt and fpt
files, if needed. An alpha code of reading index support for ndx, ntx,
mdx, idx and cdx is available for testing -- see the DBD::Index(3) man
page. Module XBase provides simple native interface to XBase files.
For DBI compliant database access, see the DBD::XBase and DBI modules
and their man pages.
The following methods are supported by XBase module:
General methods
new Creates the XBase object, loads the info about the table form the
dbf file. The first parameter should be the name of existing dbf
file (table, in fact) to read. A suffix .dbf will be appended if
needed. This method creates and initializes new object, will also
check for memo file, if needed.
The parameters can also be specified in the form of hash: value of
name is then the name of the table, other flags supported are:
memofile specifies non standard name for the associated memo file.
By default it's the name of the dbf file, with extension dbt or
fpt.
ignorememo ignore memo file at all. This is usefull if you've lost
the dbt file and you do not need it. Default is false.
memosep separator of memo records in the dBase III dbt files. The
standard says it should be "\x1a\x1a". There are however
implamentations that only put in one "\x1a". XBase.pm tries to
guess which is valid for your dbt but if it fails, you can tell it
yourself.
nolongchars prevents XBase to treat the decimal value of character
fields as high byte of the length -- there are some broken products
around producing character fields with decimal values set.
my $table = new XBase "table.dbf" or die XBase->errstr;
my $table = new XBase "name" => "table.dbf",
"ignorememo" => 1;
recompute_lastrecno forces XBase.pm to disbelieve the information
about the number of records in the header of the dbf file and
recompute the number of records. Use this only if you know that
some other software of yours produces incorrect headers.
close
Closes the object/file, no arguments.
create
Creates new database file on disk and initializes it with 0
records. A dbt (memo) file will be also created if the table
contains some memo fields. Parameters to create are passed as hash.
You can call this method as method of another XBase object and then
you only need to pass name value of the hash; the structure
(fields) of the new file will be the same as of the original
object.
If you call create using class name (XBase), you have to (besides
name) also specify another four values, each being a reference to
list: field_names, field_types, field_lengths and field_decimals.
The field types are specified by one letter strings (C, N, L, D,
...). If you set some value as undefined, create will make it into
some reasonable default.
my $newtable = $table->create("name" => "copy.dbf");
my $newtable = XBase->create("name" => "copy.dbf",
"field_names" => [ "ID", "MSG" ],
"field_types" => [ "N", "C" ],
"field_lengths" => [ 6, 40 ],
"field_decimals" => [ 0, undef ]);
Other attributes are memofile for non standard memo file location,
codepage to set the codepage flag in the dbf header (it does not
affect how XBase.pm reads or writes the data though, just to make
FoxPro happy), and version to force different version of the dbt
(dbt) file. The default is the version of the object from which you
create the new one, or 3 if you call this as class method
(XBase->create).
The new file mustn't exist yet --XBase will not allow you to
overwrite existing table. Use drop (or unlink) to delete it first.
drop
This method closes the table and deletes it on disk (including
associated memo file, if there is any).
last_record
Returns number of the last record in the file. The lines deleted
but present in the file are included in this number.
last_field
Returns number of the last field in the file, number of fields
minus 1.
field_names, field_types, field_lengths, field_decimals
Return list of field names and so on for the dbf file.
field_type, field_length, field_decimal
For a field name, returns the appropriate value. Returns undef if
the field doesn't exist in the table.
Reading the data one by one
When dealing with the records one by one, reading or writing (the
following six methods), you have to specify the number of the record in
the file as the first argument. The range is "0 ..
$table->last_record".
get_record
Returns a list of data (field values) from the specified record
(line of the table). The first parameter in the call is the number
of the record. If you do not specify any other parameters, all
fields are returned in the same order as they appear in the file.
You can also put list of field names after the record number and
then only those will be returned. The first value of the returned
list is always the 1/0 "_DELETED" value saying whether the record
is deleted or not, so on success, get_record never returns empty
list.
get_record_nf
Instead if the names of the fields, you can pass list of numbers of
the fields to read.
get_record_as_hash
Returns hash (in list context) or reference to hash (in scalar
context) containing field values indexed by field names. The name
of the deleted flag is "_DELETED". The only parameter in the call
is the record number. The field names are returned as uppercase.
Writing the data
All three writing methods always undelete the record. On success they
return true -- the record number actually written.
set_record
As parameters, takes the number of the record and the list of
values of the fields. It writes the record to the file. Unspecified
fields (if you pass less than you should) are set to undef/empty.
set_record_hash
Takes number of the record and hash as parameters, sets the fields,
unspecified are undefed/emptied.
update_record_hash
Like set_record_hash but fields that do not have value specified in
the hash retain their value.
To explicitely delete/undelete a record, use methods delete_record or
undelete_record with record number as a parameter.
Assorted examples of reading and writing:
my @data = $table->get_record(3, "jezek", "krtek");
my $hashref = $table->get_record_as_hash(38);
$table->set_record_hash(8, "jezek" => "jezecek",
"krtek" => 5);
$table->undelete_record(4);
This is a code to update field MSG in record where ID is 123.
use XBase;
my $table = new XBase "test.dbf" or die XBase->errstr;
for (0 .. $table->last_record) {
my ($deleted, $id) = $table->get_record($_, "ID")
die $table->errstr unless defined $deleted;
next if $deleted;
$table->update_record_hash($_, "MSG" => "New message")
if $id == 123;
}
Sequentially reading the file
If you plan to sequentially walk through the file, you can create a
cursor first and then repeatedly call fetch to get next record.
prepare_select
As parameters, pass list of field names to return, if no
parameters, the following fetch will return all fields.
prepare_select_with_index
The first parameter is the file name of the index file, the rest is
as above. For index types that can hold more index structures in on
file, use arrayref instead of the file name and in that array
include file name and the tag name, and optionaly the index type.
The fetch will then return records in the ascending order,
according to the index.
Prepare will return object cursor, the following method are methods of
the cursor, not of the table.
fetch
Returns the fields of the next available undeleted record. The list
thus doesn't contain the "_DELETED" flag since you are guaranteed
that the record is not deleted.
fetch_hashref
Returns a hash reference of fields for the next non deleted record.
last_fetched
Returns the number of the record last fetched.
find_eq
This only works with cursor created via prepare_select_with_index.
Will roll to the first record what is equal to specified argument,
or to the first greater if there is none equal. The following
fetches then continue normally.
Examples of using cursors:
my $table = new XBase "names.dbf" or die XBase->errstr;
my $cursor = $table->prepare_select("ID", "NAME", "STREET");
while (my @data = $cursor->fetch) {
### do something here, like print "@data\n";
}
my $table = new XBase "employ.dbf";
my $cur = $table->prepare_select_with_index("empid.ndx");
## my $cur = $table->prepare_select_with_index(
["empid.cdx", "ADDRES", "char"], "id", "address");
$cur->find_eq(1097);
while (my $hashref = $cur->fetch_hashref
and $hashref->{"ID"} == 1097) {
### do something here with $hashref
}
The second example shows that after you have done find_eq, the fetches
continue untill the end of the index, so you have to check whether you
are still on records with given value. And if there is no record with
value 1097 in the indexed field, you will just get the next record in
the order.
The updating example can be rewritten to:
use XBase;
my $table = new XBase "test.dbf" or die XBase->errstr;
my $cursor = $table->prepare_select("ID")
while (my ($id) = $cursor->fetch) {
$table->update_record_hash($cursor->last_fetched,
"MSG" => "New message") if $id == 123
}
Dumping the content of the file
A method get_all_records returns reference to an array containing array
of values for each undeleted record at once. As parameters, pass list
of fields to return for each record.
To print the content of the file in a readable form, use method
dump_records. It prints all not deleted records from the file. By
default, all fields are printed, separated by colons, one record on a
row. The method can have parameters in a form of a hash with the
following keys:
rs Record separator, string, newline by default.
fs Field separator, string, one colon by default.
fields
Reference to a list of names of the fields to print. By default
it's undef, meaning all fields.
undef
What to print for undefined (NULL) values, empty string by default.
Example of use is
use XBase;
my $table = new XBase "table" or die XBase->errstr;
$table->dump_records("fs" => " | ", "rs" => " <-+\n",
"fields" => [ "id", "msg" ]);'
Also note that there is a script dbfdump.pl(1) that does the printing.
Errors and debugging
If the method fails (returns false or null list), the error message can
be retrieved via errstr method. If the new or create method fails, you
have no object so you get the error message using class syntax
"XBase->errstr()".
The method header_info returns (not prints) string with information
about the file and about the fields.
Module XBase::Base(3) defines some basic functions that are inherited
by both XBase and XBase::Memo(3) module.
DATA TYPES
The character fields are returned "as is". No charset or other
translation is done. The numbers are converted to Perl numbers. The
date fields are returned as 8 character string of the 'YYYYMMDD' form
and when inserting the date, you again have to provide it in this form.
No checking for the validity of the date is done. The datetime field is
returned in the number of (possibly negative) seconds since 1970/1/1,
possibly with decimal part (since it allows precision up to 1/1000 s).
To get the fields, use the gmtime (or similar) Perl function.
If there is a memo field in the dbf file, the module tries to open file
with the same name but extension dbt, fpt or smt. It uses module
XBase::Memo(3) for this. It reads and writes this memo field
transparently (you do not know about it) and returns the data as single
scalar.
INDEX, LOCKS
New: A support for ndx, ntx, mdx, idx and cdx index formats is
available with alpha status for testing. Some of the formats are
already rather stable (ndx). Please read the XBase::Index(3) man page
and the eg/use_index file in the distribution for examples and ideas.
Send me examples of your data files and suggestions for interface if
you need indexes.
General locking methods are locksh, lockex and unlock for shared lock,
exclusive lock and unlock. They call flock but you can redefine then in
XBase::Base package.
INFORMATION SOURCE
This module is built using information from and article XBase File
Format Description by Erik Bachmann, URL
http://www.clicketyclick.dk/databases/xbase/format/
Thanks a lot.
VERSION
1.02
AVAILABLE FROM
http://www.adelton.com/perl/DBD-XBase/
AUTHOR
(c) 1997--2011 Jan Pazdziora.
All rights reserved. This package is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.
Contact the author at jpx dash perl at adelton dot com.
THANKS
Many people have provided information, test files, test results and
patches. This project would not be so great without them. See the
Changes file for (I hope) complete list. Thank you all, guys!
Special thanks go to Erik Bachmann for his great page about the file
structures; to Frans van Loon, William McKee, Randy Kobes and Dan
Albertsson for longtime cooperation and many emails we've exchanged
when fixing and polishing the modules' behaviour; and to Dan Albertsson
for providing support for the project.
SEE ALSOperl(1); XBase::FAQ(3); DBD::XBase(3) and DBI(3) for DBI interface;
dbfdump.pl(1)perl v5.14.1 2011-03-03 XBase(3)
