Sams Teach Yourself Ruby in 21 Days

Formatted Output

Ruby provides a highly flexible way of formatting information for output, called printf. It is borrowed from the C language, and for the convenience of C programmers (including, presumably, the author of Ruby), the formatting specifications are like those used in C's standard I/O library. So if you already program in C and are familiar with how printf works, you can skip most of this section; the main differences that you need to know are that printf is a method of IO objects (including files) whereas sprintf is not (it returns a string).

Let's start with printf. You can use it just as you use print, except you give it a format string as an extra first argument. Certain sequences of characters in the format string will be subsituted ...