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.\" ========================================================================
.\"
.IX Title "XBase 3"
.TH XBase 3 "2003-11-21" "perl v5.8.8" "User Contributed Perl Documentation"
.SH "NAME"
XBase \- Perl module for reading and writing the dbf files
.SH "SYNOPSIS"
.IX Header "SYNOPSIS"
.Vb 7
\&  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 "$id:\et$msg\en" unless $deleted;
\&  }
.Ve
.SH "DESCRIPTION"
.IX Header "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 \fIDBD::Index\fR\|(3) man
page. Module XBase provides simple native interface to XBase files.
For \s-1DBI\s0 compliant database access, see the DBD::XBase and \s-1DBI\s0 modules
and their man pages.
.PP
The following methods are supported by XBase module:
.Sh "General methods"
.IX Subsection "General methods"
.IP "new" 4
.IX Item "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.
.Sp
The parameters can also be specified in the form of hash: value of
\&\fBname\fR is then the name of the table, other flags supported are:
.Sp
\&\fBmemofile\fR specifies non standard name for the associated memo file.
By default it's the name of the dbf file, with extension dbt or fpt.
.Sp
\&\fBignorememo\fR ignore memo file at all. This is usefull if you've lost
the dbt file and you do not need it. Default is false.
.Sp
\&\fBmemosep\fR separator of memo records in the dBase \s-1III\s0 dbt files. The
standard says it should be \f(CW"\ex1a\ex1a"\fR. There are however
implamentations that only put in one \f(CW"\ex1a"\fR. XBase.pm tries to
guess which is valid for your dbt but if it fails, you can tell it
yourself.
.Sp
\&\fBnolongchars\fR 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.
.Sp
.Vb 1
\&    my $table = new XBase "table.dbf" or die XBase->errstr;
.Ve
.Sp
.Vb 2
\&    my $table = new XBase "name" => "table.dbf",
\&                                        "ignorememo" => 1;
.Ve
.Sp
\&\fBrecompute_lastrecno\fR 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.
.IP "close" 4
.IX Item "close"
Closes the object/file, no arguments.
.IP "create" 4
.IX Item "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.
.Sp
You can call this method as method of another XBase object and then
you only need to pass \fBname\fR value of the hash; the structure
(fields) of the new file will be the same as of the original object.
.Sp
If you call \fBcreate\fR using class name (XBase), you have to (besides
\&\fBname\fR) also specify another four values, each being a reference
to list: \fBfield_names\fR, \fBfield_types\fR, \fBfield_lengths\fR and
\&\fBfield_decimals\fR. 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.
.Sp
.Vb 1
\&    my $newtable = $table->create("name" => "copy.dbf");
.Ve
.Sp
.Vb 5
\&    my $newtable = XBase->create("name" => "copy.dbf",
\&                "field_names" => [ "ID", "MSG" ],
\&                "field_types" => [ "N", "C" ],
\&                "field_lengths" => [ 6, 40 ],
\&                "field_decimals" => [ 0, undef ]);
.Ve
.Sp
Other attributes are \fBmemofile\fR for non standard memo file location,
\&\fBcodepage\fR 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 \fBversion\fR 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).
.Sp
The new file mustn't exist yet \*(-- XBase will not allow you to
overwrite existing table. Use \fBdrop\fR (or unlink) to delete it first.
.IP "drop" 4
.IX Item "drop"
This method closes the table and deletes it on disk (including
associated memo file, if there is any).
.IP "last_record" 4
.IX Item "last_record"
Returns number of the last record in the file. The lines deleted but
present in the file are included in this number.
.IP "last_field" 4
.IX Item "last_field"
Returns number of the last field in the file, number of fields minus 1.
.IP "field_names, field_types, field_lengths, field_decimals" 4
.IX Item "field_names, field_types, field_lengths, field_decimals"
Return list of field names and so on for the dbf file.
.IP "field_type, field_length, field_decimal" 4
.IX Item "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.
.Sh "Reading the data one by one"
.IX Subsection "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
\&\f(CW\*(C`0 .. $table\->last_record\*(C'\fR.
.IP "get_record" 4
.IX Item "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 \f(CW\*(C`_DELETED\*(C'\fR value saying whether the record is deleted or not, so
on success, \fBget_record\fR never returns empty list.
.IP "get_record_nf" 4
.IX Item "get_record_nf"
Instead if the names of the fields, you can pass list of numbers of
the fields to read.
.IP "get_record_as_hash" 4
.IX Item "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 \f(CW\*(C`_DELETED\*(C'\fR. The only parameter in the call is
the record number. The field names are returned as uppercase.
.Sh "Writing the data"
.IX Subsection "Writing the data"
All three writing methods always undelete the record. On success they
return true \*(-- the record number actually written.
.IP "set_record" 4
.IX Item "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.
.IP "set_record_hash" 4
.IX Item "set_record_hash"
Takes number of the record and hash as parameters, sets the fields,
unspecified are undefed/emptied.
.IP "update_record_hash" 4
.IX Item "update_record_hash"
Like \fBset_record_hash\fR but fields that do not have value specified
in the hash retain their value.
.PP
To explicitely delete/undelete a record, use methods \fBdelete_record\fR
or \fBundelete_record\fR with record number as a parameter.
.PP
Assorted examples of reading and writing:
.PP
.Vb 5
\&    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);
.Ve
.PP
This is a code to update field \s-1MSG\s0 in record where \s-1ID\s0 is 123.
.PP
.Vb 9
\&    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;
\&    }
.Ve
.Sh "Sequentially reading the file"
.IX Subsection "Sequentially reading the file"
If you plan to sequentially walk through the file, you can create
a cursor first and then repeatedly call \fBfetch\fR to get next record.
.IP "prepare_select" 4
.IX Item "prepare_select"
As parameters, pass list of field names to return, if no parameters,
the following \fBfetch\fR will return all fields.
.IP "prepare_select_with_index" 4
.IX Item "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 \fBfetch\fR will then return records in the ascending order,
according to the index.
.PP
Prepare will return object cursor, the following method are methods of
the cursor, not of the table.
.IP "fetch" 4
.IX Item "fetch"
Returns the fields of the next available undeleted record. The list
thus doesn't contain the \f(CW\*(C`_DELETED\*(C'\fR flag since you are guaranteed
that the record is not deleted.
.IP "fetch_hashref" 4
.IX Item "fetch_hashref"
Returns a hash reference of fields for the next non deleted record.
.IP "last_fetched" 4
.IX Item "last_fetched"
Returns the number of the record last fetched.
.IP "find_eq" 4
.IX Item "find_eq"
This only works with cursor created via \fBprepare_select_with_index\fR.
Will roll to the first record what is equal to specified argument, or
to the first greater if there is none equal. The following \fBfetch\fRes
then continue normally.
.PP
Examples of using cursors:
.PP
.Vb 5
\&    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\en";
\&    }
.Ve
.PP
.Vb 9
\&    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
\&    }
.Ve
.PP
The second example shows that after you have done \fBfind_eq\fR, the
\&\fBfetch\fRes 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.
.PP
The updating example can be rewritten to:
.PP
.Vb 7
\&    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   
\&    }
.Ve
.Sh "Dumping the content of the file"
.IX Subsection "Dumping the content of the file"
A method \fBget_all_records\fR 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.
.PP
To print the content of the file in a readable form, use method
\&\fBdump_records\fR. 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:
.IP "rs" 4
.IX Item "rs"
Record separator, string, newline by default.
.IP "fs" 4
.IX Item "fs"
Field separator, string, one colon by default.
.IP "fields" 4
.IX Item "fields"
Reference to a list of names of the fields to print. By default it's
undef, meaning all fields.
.IP "undef" 4
.IX Item "undef"
What to print for undefined (\s-1NULL\s0) values, empty string by default.
.PP
Example of use is
.PP
.Vb 4
\&    use XBase;
\&    my $table = new XBase "table" or die XBase->errstr;
\&    $table->dump_records("fs" => " | ", "rs" => " <-+\en",
\&                        "fields" => [ "id", "msg" ]);'
.Ve
.PP
Also note that there is a script \fIdbfdump\fR\|(1) that does the printing.
.Sh "Errors and debugging"
.IX Subsection "Errors and debugging"
If the method fails (returns false or null list), the error message
can be retrieved via \fBerrstr\fR method. If the \fBnew\fR or \fBcreate\fR
method fails, you have no object so you get the error message using
class syntax \f(CW\*(C`XBase\->errstr()\*(C'\fR.
.PP
The method \fBheader_info\fR returns (not prints) string with
information about the file and about the fields.
.PP
Module \fIXBase::Base\fR\|(3) defines some basic functions that are inherited
by both XBase and \fIXBase::Memo\fR\|(3) module.
.SH "DATA TYPES"
.IX Header "DATA TYPES"
The character fields are returned \*(L"as is\*(R". 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 '\s-1YYYYMMDD\s0' 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.
.PP
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
\&\fIXBase::Memo\fR\|(3) for this. It reads and writes this memo field
transparently (you do not know about it) and returns the data as
single scalar.
.SH "INDEX, LOCKS"
.IX Header "INDEX, LOCKS"
\&\fBNew:\fR 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 \fIXBase::Index\fR\|(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.
.PP
General locking methods are \fBlocksh\fR, \fBlockex\fR and \fBunlock\fR for
shared lock, exclusive lock and unlock. They call flock but you can
redefine then in XBase::Base package.
.SH "INFORMATION SOURCE"
.IX Header "INFORMATION SOURCE"
This module is built using information from and article XBase File
Format Description by Erik Bachmann, \s-1URL\s0
.PP
.Vb 1
\&        http://www.e-bachmann.dk/docs/xbase.htm
.Ve
.PP
Thanks a lot.
.SH "VERSION"
.IX Header "VERSION"
0.241
.SH "AUTHOR"
.IX Header "AUTHOR"
(c) 1997\-\-2003 Jan Pazdziora, adelton@fi.muni.cz,
http://www.fi.muni.cz/~adelton/ at Faculty of Informatics, Masaryk
University in Brno, Czech Republic
.PP
All rights reserved. This package is free software; you can
redistribute it and/or modify it under the same terms as Perl itself.
.SH "THANKS"
.IX Header "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!
.PP
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.
.SH "SEE ALSO"
.IX Header "SEE ALSO"
\&\fIperl\fR\|(1); \fIXBase::FAQ\fR\|(3); \fIDBD::XBase\fR\|(3) and \s-1\fIDBI\s0\fR\|(3) for \s-1DBI\s0 interface;
\&\fIdbfdump\fR\|(1)
Creat By MiNi SheLL
Email: devilkiller@gmail.com