Hour 15. Finding Permanence

Writing Perl programs that find data in files or interact with the user is fine. But what happens when the program ends? The results are gone, you've got nothing to show for your effort, and you're left with this empty feeling—as though nothing had happened at all.

That's what databases are all about. Databases are for storing data for later use. A properly designed database can be used by many kinds of programs for queries, reports, and data entry. To design a database, you need to think carefully about what kind of data you want to store and how you want to store it. Another consideration is how the data will be accessed: by one person at a time or by many users simultaneously.

In this hour, you'll learn about a couple different methods for storing data for later retrieval.

In this hour you'll learn how to

• Create a DBM file and store data in it

• Treat regular text files as a database

• Read and write to random positions in files

• Lock files for concurrent access