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Ruby comes with a code profiler built in, and all you have to do to have your code profiled automatically is to add require "profile" to the start of your code, or run it with ruby --r profile before your source file name.

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n this chapter we re going to look at how to store, process, and interact with external sources of data from our Ruby programs. In 4 we briefly looked at how to load files to get data into an application, but this chapter will extend upon that greatly and allow you to create files from scratch from your Ruby programs. Later in this chapter we ll look at databases specialized organizations of data and how to interact with them, along with some notes on interacting with popular database systems such as SQLite, MySQL, PostgreSQL, Oracle, and Microsoft SQL Server. You can use databases for simple tasks such as storing information about a small set of items or as an address book, but databases are also used in the world s busiest data processing environments. By the end of this chapter, you ll be able to use databases the same way as, or at least in a similar way to, those used by professional developers around the world.

As you sketch the rest of the Explanation and Detail slides, use the range of graphical possibilities as described in 7 to sketch the slide headlines and then to add graphics, as shown in Figure 9-13. As you saw in earlier chapters, these graphics might include photos, screen captures, diagrams, charts, or other media elements. Add a navigation bar to your custom layouts for the Explanation and Detail slides to provide a cue to the presentation s organization and also to consistently carry through the visual motif in the form of a hurdle in the lower-right corner of each slide.

The names num and result are quite arbitrary in this example, but return is important. The return statement is used to return something from the function (which is also how we used it in the preceding hello function).

Interaction, in computer terms, relates to the input and output of data, or I/O for short. Most programming languages have built-in support for I/O, and Ruby s is particularly well designed. I/O streams are the basis for all input and output in Ruby. An I/O stream is a conduit or channel for input and output operations between one resource and another. Usually this will be between your Ruby program and the keyboard, or between your Ruby program and a file. Along this stream, input and output operations can take place. In some cases, such as when using the keyboard, only input can be retrieved, as you can t send data to a keyboard, and data can only be sent to, and not from, the screen. In this section we re going to look at using the keyboard, using files, and other forms of I/O in Ruby and how they can be used.

The simplest way to get external data into a program is to use the keyboard. For example:

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case and assigns it to a. You then print it, using puts, to the standard output the screen in this case.

The standard input is a default stream supplied by many operating systems that relates to the standard way to accept input from the user. In our case, the standard input is the keyboard, but if, for example, you were to redirect data to a Ruby application from a Unix-like operating system, such as Linux or Mac OS X, the standard input would be the data piped to it. For example: