Perl Installation Notes

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Perl Installation Notes

The Perl DBI module provides a generic interface for database access. You can write a DBI script that works with many different database engines without change. To use DBI, you must install the DBI module, as well as a DataBase Driver (DBD) module for each type of database server you want to access. For MySQL, this driver is the DBD::mysql module.

Installing Perl on Unix

MySQL Perl support requires that you have installed MySQL client programming support (libraries and header files). Most installation methods install the necessary files. If you install MySQL from RPM files on Linux, be sure to install the developer RPM as well. The client programs are in the client RPM, but client programming support is in the developer RPM.

The files you need for Perl support can be obtained from the CPAN (Comprehensive Perl Archive Network) at http://search.cpan.org.

The easiest way to install Perl modules on Unix is to use the CPAN module. For example:
shell> perl -MCPAN -e shell
cpan> install DBI
cpan> install DBD::mysql

The DBD::mysql installation runs a number of tests. These tests attempt to connect to the local MySQL server using the default user name and password. (The default user name is your login name on Unix, and ODBC on Windows. The default password is “no password.”) If you cannot connect to the server with those values (for example, if your account has a password), the tests fail. You can use force install DBD::mysql to ignore the failed tests.

DBI requires the Data::Dumper module. It may be installed; if not, you should install it before installing DBI.

It is also possible to download the module distributions in the form of compressed tar archives and build the modules manually. For example, to unpack and build a DBI distribution, use a procedure such as this:

1. Unpack the distribution into the current directory:

shell> gunzip < DBI-VERSION.tar.gz | tar xvf –

This command creates a directory named DBI-VERSION.

2. Change location into the top-level directory of the unpacked distribution:
shell> cd DBI-VERSION
3. Build the distribution and compile everything:
shell>  perl Makefile.PL
shell>  Make
shell>  Make test
shell>  Make install

The make test command is important because it verifies that the module is working. Note that when you run that command during the DBD::mysql installation to exercise the interface code, the MySQL server must be running or the test fails.

It is a good idea to rebuild and reinstall the DBD::mysql distribution whenever you install a new release of MySQL. This ensures that the latest versions of the MySQL client libraries are installed correctly.

If you do not have access rights to install Perl modules in the system directory or if you want to install local Perl modules, the following reference may be useful: http://learn.perl.org/faq/perlfaq8.html#How-do-I-keep-my-own-module-library-directory-

Problems Using the Perl DBI/DBD Interface

If Perl reports that it cannot find the ../mysql/mysql.so module, the problem is probably that Perl cannot locate the libmysqlclient.so shared library. You should be able to fix this problem by one of the following methods:
• Copy libmysqlclient.so to the directory where your other shared libraries are located (probably /usr/lib or /lib).
• Modify the -L options used to compile DBD::mysql to reflect the actual location of libmysqlclient.so.
• On Linux, you can add the path name of the directory where libmysqlclient.so is located to the /etc/ld.so.conf file.
•Add the path name of the directory where libmysqlclient.so is located to the LD_RUN_PATH environment variable. Some systems use LD_LIBRARY_PATH instead.

Note that you may also need to modify the -L options if there are other libraries that the linker fails to find. For example, if the linker cannot find libc because it is in /lib and the link command specifies -L/usr/lib, change the -L option to -L/lib or add -L/lib to the existing link command.

If you get the following errors from DBD::mysql, you are probably using gcc (or using an old binary compiled with gcc):

/usr/bin/perl: can’t resolve symbol ‘__moddi3’
/usr/bin/perl: can’t resolve symbol ‘__divdi3’

Add -L/usr/lib/gcc-lib/… -lgcc to the link command when the mysql.so library gets built (check the output from make for mysql.so when you compile the Perl client). The -L option should specify the path name of the directory where libgcc.a is located on your system.

Another cause of this problem may be that Perl and MySQL are not both compiled with gcc. In this case, you can solve the mismatch by compiling both with gcc.

 

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