1XBase::FAQ(3) User Contributed Perl Documentation XBase::FAQ(3)
2
6 XBase::FAQ - Frequently asked questions about the XBase.pm/DBD::XBase
7 modules
8
10 This is a list of questions people asked since the module has been
11 announced in fall 1997, and my answers to them.
12
14 Jan Pazdziora, adelton@fi.muni.cz
15
17 What Perl version do I need? What other modules?
18 You need perl at least 5.004. I test each new distribution agains
19 5.005* and 5.004_04 version of perl. You need DBI module version 1.00
20 or higher, if you want to use the DBD driver (which you should).
21 Can I use XBase.pm under Windows 95/NT?
23 Yes. It's a standard Perl module so there is no reason it shouldn't.
24 Or, actually, there are a lot of reasons why standard thing do not
25 work on systems that are broken, but I'm trying hard to workaround
26 these bugs. If you find a problem on these platform, send me a
27 description and I'll try to find yet another workaround.
28 Is there a choice of the format of the date?
30 The only possible format in which you can get the date and that the
31 module expect for inserts and updates is a 8 char string 'YYYYMMDD'.
32 It is not possible to change this format. I prefer to do the
33 formating myself since you have more control over it.
34 The "get_record" also returns deleted records. Why?
36 Because. You get the _DELETED flag as the first value of the array.
37 This gives you a possibility to decide what to do -- undelete,
38 ignore... It's a feature -- you say you want a record of given
39 number, you get it and get additional information, if the record is
40 or isn't marked deleted.
41 But with DBD::XBase, I do not see the deleted records.
43 That's correct: DBD::XBase only gives you records that are positively
44 in the file and not deleted. Which shows that XBase.pm is a lower
45 level tool because you can touch records that are marked deleted,
46 while DBD::XBase is higher level -- it gives you SQL interface and
47 let's you work with the file more naturaly (what is deleted should
48 stay deleted).
49 XBase.pm cannot read files created with [your favorite tool].
51 Describe exactly, what you expect and what you get. Send me the file
52 (I understand attachments, uuencode, tar, gzip and zip) so that I can
53 check what it going on and make XBase.pm undestand your file. A
54 small sample (three rows, or so) are generally enough but you can
55 send the whole file if it doesn't have megabytes. Please understand
56 How to install the module when I do not have make?
58 On Win* platform and with ActiveState port, use ppm to install
59 DBD::XBase from ActiveState's site. You can also just copy the files
60 from the lib directory of the distribution to where perl can find
61 them. Also check whether your make doesn't hide under different names
62 (nmake, gmake). See "README".
63 I have make but I cannot install into default directory.
65 Ask your sysadmin to do it for your. If he refuses, fire the
66 sysadmin. See "README" for how to install into and use nonstandard
67 place for the module.
68 Can I access one dbf file both from Perl and (say) Clipper?
70 For reading -- yes. For writing -- XBase.pm has a locksh and lockex
71 method to lock the file. The question is to what extend Clipper (or
72 Fox* or whatever) uses the same system calls, documentation of native
73 XBase applications doesn't tell this. So the answer is that for
74 multiple updates you should probably consider real RDBMS system
75 (PostgreSQL, MySQL, Oracle, to name a few).
76 XBase.pm/DBD::XBase breaks my accented characters.
78 No, it doesn't. The character data is returned exactly as it appears
79 in the dbf/dbt file. You probably brought the file from different
80 system that uses differend character encodings. So some bytes in the
81 strings have different meaning on that system. You also probably have
82 fonts in different encoding on that system. In the Czech language, we
83 have about 6 different encoding that affect possition at which
84 accented characters appear.
85 So what you really want to do is to use some external utility to
87 convert the strings to encoding you need -- for example, when I bring
88 the dbf from Win*, it often is in the Windows-1250 or PC-Latin-2
89 encoding, while the standard is ISO-8859-2. I use my utility
90 Cz::Cstocs to do the conversion, you maight also try GNU program
91 recode or use Text::Iconv Perl module.
92 How do I access the fields in the memo file?
94 Just read the memo field, it will fetch the data from the memo file
95 for you transparently.
96 Matching with "field = '%str%'" doesn't work.
98 If you want to match wildcards with DBD::XBase, you have to use
99 "like":
100 select * from table where field like '%str%'
102 Can I sue you if XBase.pm/DBD::XBase corrupts my data?
104 No. At least, I hope no. The software is provided without any
105 warranty, in a hope you might find is usefull. Which is by the way
106 the same as with most other software, even if you pay for that. What
107 is different with XBase.pm/DBD::XBase is the fact that if you find
108 out that the results are different from those expected, you are
109 welcome to contact me, describe the problem and send me the files
110 that give troubles to the module, and I'll try to find fix the
111 module.
112 What dbf/other files standard does the module support?
114 I try to support any file that looks reasonably as
115 dbf/dbt/fpt/smt/ndx/ntx/mdx/idx/cdx. There are many clones of XBase-
116 like software, each adding its own extension. The module tries to
117 accept all different variations. To do that, I need your cooperation
118 however -- usually good description of the problem, file sample and
119 expected results lead to rather fast patch.
120 What SQL standard does the DBD::XBase support?
122 If supports a reasonable subset of the SQL syntax, IMHO. So you can
123 do select, delete, insert and update, create and drop table. If there
124 is something that should be added, let me know and I will consider
125 it. Having said that, I do not expect to ever support joins, for
126 example. This module is more a parser to read files from your legacy
127 applications that a RDBMS -- you can find plenty of them around --
128 use them.
129 I downloaded you module I do not know how to install it.
131 Did you follow the steps in the "README" and "INSTALL" files? Where
132 did it fail? This module uses a standard way modules in Perl are
133 installed. If you've never installed a module on your system and your
134 system is so non-standard that the general instruction do not help,
135 you should contact your system administrator or the support for your
136 system.
137 "select max(field) from table" does not work.
139 Aggregate functions are not supported. It would probably be very
140 slow, since the DBD doesn't make use of indexes at the moment. I do
141 not have plans to add this support in some near future.
142 "DBI->connect" says that the directory doesn't exist ...
144 ... but it's there. Is DBD::XBase mad or what?
145 The third part of the first parameter to the connect is the directory
147 where DBD::XBase will look for the dbf files. During connect, the
148 module checks "if -d $directory". So if it says it's not there, it's
149 not there and the only thing DBD::XBase can do about it is to report
150 it to you. It might be that the directory is not mounted, you do not
151 have permissions to it, the script is running under different UID
152 than when you try it from command line, or you use relative patch and
153 run the script from a different directory (pwd) than you expect.
154 Anyway, add
155 die "Error reading $dir: $!\n" unless -d $dir;
157 to your script and you will see that it's not DBD::XBase problem.
159 The XBase.pm/dbfdump.pl stops after reading n records ...
161 ... why doesn't it read all 10 x n records?
162 Check if the file isn't truncated. "dbfdump.pl -i file.dbf" will tell
164 you the expected number of records and length of one record, like
165 Filename: file.dbf
167 Version: 0x03 (ver. 3)
168 Num of records: 65
169 Header length: 1313
170 Record length: 1117
171 Last change: 1998/12/18
172 Num fields: 40
173 So the expected length of the file is at least 1313 + 65 * 1117. If
175 it's shorter, you've got damaged file and XBase.pm/dbfdump.pl only
176 reads as much rows as it can find in the dbf.
177 How is this DBD::XBase related to DBD::ODBC?
179 DBD::XBase reads the dbf files directly, using the (included)
180 XBase.pm module. So it will run on any platform with reasonable new
181 perl. With DBD::ODBC, you need an ODBC server, or some program, that
182 DBD::ODBC could talk to. Many proprietary software can serve as ODBC
183 source for dbf files, it just doesn't seem to run on Un*x systems.
184 And is also much more resource intensive, if you just need to read
185 the file record by record and convert it to HTML page or do similary
186 simple operation with it.
187 How do I pack the dbf file, after the records were deleted?
189 XBase.pm doesn't support this directly. You'd probably want to create
190 new table, copy the data and rename back. Patches are always welcome.
191 Foxpro doesn't see all fields in dbf created with XBase.pm.
193 Put 'version' => 3 options in to the create call -- that way we say
194 that the dbf file is dBaseIII style.
195perl v5.12.0 2010-05-06 XBase::FAQ(3)