Using the irb Command (with examples)

1: Start the interactive shell

Code:

irb

Motivation:

The irb command is used to start the Interactive Ruby Shell, which provides an interactive environment for executing Ruby code. It is useful for quickly testing code snippets, exploring APIs, and debugging.

Explanation:

By simply typing irb in the command line, the Ruby interpreter launches the interactive shell, allowing us to enter and execute Ruby code interactively. This can be helpful when we need to experiment with code without having to create a separate Ruby script.

Example Output:

irb(main):001:0>

The irb(main):001:0> is the terminal prompt in the Ruby interactive shell, indicating that the shell is ready to accept Ruby code input.

2: Execute Ruby code from stdin

Code:

irb --noinspect < file.rb

Motivation:

The -noinspect flag helps to prevent the inspection of objects and makes the output more readable when executing Ruby code from a file.

Explanation:

By running the irb command with the --noinspect flag, we can execute Ruby code contained in a file directly from the command line. This can be useful when we have a Ruby file with code that we want to evaluate without manually typing each line into the interactive shell.

Example Output:

2

The output would vary depending on the code in the file, but in this example, the value 2 is the result of the evaluated Ruby code.

3: Access IRB documentation

Code:

irb --help

Motivation:

The irb command provides a convenient way to access the documentation for the Interactive Ruby Shell, which can be helpful for learning about its features and options.

Explanation:

When running irb with the --help flag, it displays a list of available command-line options and their descriptions. This can be useful for quickly referencing the options and functionalities of the Interactive Ruby Shell.

Example Output:

Usage: irb ...
    -e command         one line of script. Several -e's allowed. Omitted if file given
    -r library         additional $LOAD_PATH. May be used more than once
    ...

The output would list the available command-line options and their descriptions, which can be used to customize the behavior of the irb command.

4: Customize the Ruby environment

Code:

irb -r ./custom_lib.rb

Motivation:

The -r flag allows us to load additional libraries or custom code files before starting the Interactive Ruby Shell. This is useful when we want to customize the Ruby environment with our own code or external libraries.

Explanation:

By using the -r flag followed by the path to a Ruby code file, we can load that file as part of the Ruby environment when starting the interactive shell. This allows us to execute code from the file directly within the shell.

Example Output:

irb(main):001:0> CustomLib.foo
=> "Hello, World!"

Assuming custom_lib.rb defines a class or module CustomLib with a method foo, we can call that method within the interactive shell after loading the file using the -r flag. In this example, the output is "Hello, World!" which is the result of calling the foo method.