Ruby Syntax

Let's write a simple Ruby program. All Ruby files have the extension .rb. So, place the following source code in the test.rb file.

Online Example

#!/usr/bin/ruby　-w
　
puts "Hello, Ruby!";

Here, assume that your /usr/There is already an available Ruby interpreter in the bin directory. Now, try running this program as follows:

$ ruby test.rb

This will produce the following result:

Hello, Ruby!

You have already seen a simple Ruby program; now let's look at some basic concepts related to Ruby syntax:

whitespace in Ruby programs

Whitespace characters in Ruby code, such as spaces and tabs, are generally ignored unless they appear in strings, in which case they are not ignored. However, sometimes they are used to clarify ambiguous statements. When enabled -a warning will be generated when the w option is used.

Example:

a　+　b is interpreted as a+b (This is a local variable)
a　　+b is interpreted as a(b)+b) (This is a method call)

the end of a line in a Ruby program

Ruby interprets the semicolon and newline as the end of a statement. However, if Ruby encounters an operator at the end of a line, such as +、- or backslash, which indicates the continuation of a statement.

Ruby Identifier

An identifier is the name of a variable, constant, or method. Ruby identifiers are case-sensitive. This means Ram and RAM are two different identifiers in Ruby.

The name of a Ruby identifier can contain letters, numbers, and underscore characters (_).

Reserved Words

The following table lists the reserved words in Ruby. These reserved words cannot be used as constant or variable names. However, they can be used as method names.

Here Document in Ruby

"Here Document" refers to the creation of multi-line strings. After <<, you can specify a string or identifier to terminate the string, and all lines from the current line to the terminator are the value of the string.

If the terminator is enclosed in quotes, the type of quotes determines the line-oriented string type. Please note that there should be no space between << and the terminator.

Below are different examples:

Online Example

#!/usr/bin/ruby　-w
#　-*-　coding : utf-8　-*-
　
print <<EOF
　　　　This is the first way to create a here document.
　　　　Multi-line string.
EOF
　
print <<"EOF"; # Same as above
　　　　This is the second way to create a here document.
　　　　Multi-line string.
EOF
　
print <<`EOC` # Execute command
　　　　echo hi there
　　　　echo lo there
EOC
　
print <<"foo", <<"bar" # You can stack them
　　　　I said foo.
foo
　　　　I said bar.
bar

This will produce the following result:

This is the first way to create a here document.
Multi-line string.
This is the second way to create a here document.
Multi-line string.
hi there
lo there
I said foo.
I said bar.

Ruby BEGIN Statement

Syntax

BEGIN {
　　　code
}

Declaration code It will be called before the program runs.

Online Example

#!/usr/bin/ruby
　
puts "This is the main Ruby program"
　
BEGIN {
　　　puts "Initialize Ruby Program"
}

This will produce the following result:

Initialize Ruby Program
This is the main Ruby program

Ruby END Statement

Syntax

END {
　　　code
}

Declaration code It will be called at the end of the program.

Online Example

#!/usr/bin/ruby
　
puts "This is the main Ruby program"
　
END {
　　　puts "Stop Ruby Program"
}
BEGIN {
　　　puts "Initialize Ruby Program"
}

This will produce the following result:

Initialize Ruby Program
This is the main Ruby program
Stop Ruby Program

Ruby Comments

Comments hide a line, or part of a line, or several lines from the Ruby interpreter. You can use the character (#) at the beginning of a line:

# I am a comment, please ignore me.

Or, comments can follow the same line as the statement or expression:

name = "Madisetti" # This is also a comment

You can comment multiple lines, as shown below:

# This is a comment.
# This is also a comment.
# This is also a comment.
# This is still a comment.

Below is another form. This block comment hides =begin from the interpreter/Lines between =end:

=begin
This is a comment.
This is also a comment.
This is also a comment.
This is still a comment.
=end