Learning Ruby

Chapter 8. Working with Files

You can manipulate file directories (folders) and files from within Ruby programs using methods from the Dir and File classes. There are other related classes, such as FileUtils, with lots of interesting methods, but we’ll narrow our focus to methods from Dir and File.

Most of the methods I’ll show you are class methods—that is, the method name is prefixed by the class name, as in File.open and File::open (you can use either :: or . to separate the class and method names).

Ruby uses a number of global constants (for a complete list, see Appendix A). Two global constants that are important in working with files are ARGV (or $*) and ARGF (or $<). Like Perl’s @ARGV, Ruby’s ARGV is an array that contains all the command-line arguments passed to a program. ARGF provides an I/O-like stream that allows access to a virtual concatenation of all files provided on the command line, or standard input if no files are provided. I’ll demonstrate both ARGV and ARGF later in the chapter.

Let’s start working with directories.

Directories

You can navigate directory structures on your computer with class methods from the Dir class. I’ll highlight three here: Dir.pwd, Dir.chdir (or Dir.getwd), and Dir.mkdir.

First, I’ll change directories (using an absolute path), and then store the value of the directory path in a variable.

Dir.chdir( "/Users/mikejfz" )
home = Dir.pwd # => "/Users/mikejfz/"
p home # => "/Users/mikejfz"

Compare a variable storing a directory path with the current ...