I'll Have My People Call Your People

Building a web-based telephone book can be easy, as long as you don't drink too much of Marcel's wine while you work.

Bon soir, mes amis. It is so very good to see you again. What? No, François, I do not think this is a good time. We have guests. Take a message and I will call later. Forgive me, mes amis. François has been run off his feet since we started distributing our new on-line phone book. My impetuous waiter put our name as a default record in each of the databases, and now everyone is calling! Mon Dieu!

The phone book? But, of course. In fact, in honor of this month's issue celebrating “The People Behind Linux”, we are cooking up a web-based telephone book made with rich, yet low-calorie, open-source software and our secret ingredient, Linux. I think you will find the recipe quite enjoyable and practical too, non? What is the point of knowing all these people if you never talk to them? That is why François' mother insisted that her name be put in. I jest. Please sit, mes amis, while I show you how to create your own web-based telephone book, which is sure to become a centerpiece of your intranet. For added spice, this wonder of the intranet even provides an IN/OUT board.

François! Bring some wine for our guests. Vite!

Figure 1. The web phonebook's search screen

Before we get into the meat of this recipe, may I suggest that you look at Figure 1 which shows the administration search screen. The standard user's screen is similar, but does not have the option to add a user. Figure 2 shows the results of a fairly wide search. Note the gray and red buttons that allow you to modify or delete an entry.

Figure 2. Administration Search Results Screen

Our telephone book is written entirely in Perl and uses PostgreSQL to store its entries. Before I get too far, I will tell you what you will need,

  • PostgreSQL

  • DBD and DBI modules for PostgreSQL from CPAN

  • The cgi-lib.pl Perl library

In all likelihood, Perl is already loaded on your system. Most distributions include it as part of the standard install. You should also have the Apache web server running. Again, it is extremely likely that you installed Apache with your system.

Preparation

PostgreSQL can be found at the official PostgreSQL site and, in most cases, on your Linux distribution CD. For my Red Hat system, it was simply a matter of installing PostgreSQL with the rpm command.

rpm -ivh postgresql-6.5.2-1.i386.rpm
rpm -ivh postgresql-devel-6.5.2-1.i386.rpm
rpm -ivh postgresql-server.6.5.2-1.i386.rpm

Depending on when you obtain and load PostgreSQL, the numbers may vary. Part of what happens during this installation is to create a postgres user. After assigning a password to this user, log in as postgres and initialize the database environment. Remember that the paths may vary depending on your installation.

initdb --pglib=/usr/lib/pgsql --pgdata=/var/lib/pgsql
Next, you will need to create some default PostgreSQL users. If you are installing as root (for access to Perl directories, cgi directories, etc.), then root will have to be added. So will the user “nobody”. This is often the user of your httpd server. Some have a user called “www” to run web services. I will use “nobody” as mine, and you may use whatever your server is configured for. Start by logging in as your postgres user, and execute the following command to add the users root and nobody to your PostgreSQL system:
createuser root
You'll be prompted for root's UID (accept the default) and whether user root is allowed to create databases. Answer “y”. When asked whether root is allowed to create users, I answered “n”. Now, do the same thing for user nobody. The only difference is that I answer “n” to the question of whether nobody is allowed to create databases as well. Depending on which version of PostgreSQL you are using, the question of whether a user is allowed to create other users may be worded this way:
Is user "whoever" a superuser?
The answer is still n, or “no”. Finally, with the creation of nobody, you will then be asked whether createuser should create a database for nobody. Answer “y” and you are finished creating users.

Both the DBD and DBI module can be found at the CPAN FTP site, a huge Perl resource on the web. Since the two modules are in slightly different directories, I will give you both: ftp://ftp.cpan.org/CPAN/modules/by-module/DBI/ and ftp://ftp.cpan.org/CPAN/modules/by-module/DBD/.

At the time of this writing, the latest and greatest DBI version was DBI-1.13.tar.gz, whereas DBD weighed in at a comfortable DPD-Pg-0.93.tar.gz.

The DBI module is common to all the various databases, but the DBD module must be specific. DBD modules are available for numerous databases such as Oracle, Informix and, of course, PostgreSQL. DBI is an application program interface (API) for Perl5 to interface with database systems. The idea is to provide a consistent set of modules and calls so that database access code is portable without too much fuss. Since each database will vary somewhat, however, the DBD module comes into play to take those differences into consideration.

For more information on how DBI works, try this address: www.isc.org/services/public/lists/dbi-lists.html. You do not need the information in order to be able to cook up today's recipe, but it makes for interesting reading later.

Install the DBI module first by unpacking the distributions into some temporary directory and following these steps:

cd /usr/local/temp_dir
tar -xzvf DBI-1.13.tar.gz
cd DBI-1.13
perl Makefile.PL
make
make test
make install

Tres simple. To install the DBD module, the process is similar. The latest version of the DBD module now requires you to set a couple of environment variables before the install can occur. These are POSTGRES_LIB and POSTGRES_INCLUDE.

POSTGRES_LIB=/usr/lib/pgsql
export POSTGRES_LIB
POSTGRES_INCLUDE=/usr/include/pgsql
export POSTGRES_INCLUDE
Now, you can run the install:
cd /usr/local/temp_dir
tar -xzvf DBD-Pg-0.93.tar.gz
cd DBD-Pg-0.93
perl Makefile.PL
make
make test
make install
The final ingredient you will need is the cgi-lib.pl library for Perl. This has become a virtual (de facto) standard for CGI design using forms. Surf over to the following address and save the file into your /usr/lib/perl5 directory: http://cgi-lib.berkeley.edu/.

If your Perl libraries live in a different directory (e.g., /usr/local/lib/perl5), you will need to modify the require /usr/lib/perl5/cgi-lib.pl line near the top of each cgi-bin perl script to reflect your own directory structure.

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